MAX18 28V Internal Switch Step-Up DC-DC Conerter · 2015. 4. 16. · General Description The MAX618...

General DescriptionThe MAX618 CMOS, PWM, step-up DC-DC converter generates output voltages up to 28V and accepts inputs from +3V to +28V. An internal 2A, 0.3Ω switch eliminates the need for external power MOSFETs while supplying output currents up to 500mA or more. A PWM control scheme combined with Idle Mode™ operation at light loads minimizes noise and ripple while maximizing effi-ciency over a wide load range. No-load operating current is 500μA, which allows efficiency up to 93%.A fast 250kHz switching frequency allows the use of small surface-mount inductors and capacitors. A shut-down mode extends battery life when the device is not in use. Adaptive slope compensation allows the MAX618 to accommodate a wide range of input and output voltages with a simple, single compensation capacitor.The MAX618 is available in a thermally enhanced 16-pin QSOP package that is the same size as an industry-standard 8-pin SO but dissipates up to 1W. An evaluation kit (MAX618EVKIT) is available to help speed designs.

Applications Industrial +24V and +28V Systems LCD Displays Palmtop Computers

Features Adjustable Output Voltage Up to +28V Up to 93% Efficiency Wide Input Voltage Range (+3V to +28V) Up to 500mA Output Current at +12V 500μA Quiescent Supply Current 3μA Shutdown Current 250kHz Switching Frequency Small 1W, 16-Pin QSOP Package

Idle Mode is a trademark of Maxim Integrated Products, Inc.

+Denotes a lead(Pb)-free/RoHS-compliant package.

PART TEMP. RANGE PIN-PACKAGEMAX618EEE+ -40°C to +85°C 16 QSOP

PGND

LX

FBVL

VOUTUP TO28V

COMP

IN

SHDN

GND

VIN3V TO

28V MAX618

16

15

14

13

12

11

10

9

1

2

3

4

5

6

7

8

GND GND

PGND

PGND

PGND

GND

VL

IN

GND

TOP VIEW

MAX618

QSOP

LX

LX

COMP

LX

SHDN

FB

GND

+

MAX618 28V Internal Switch, Step-Up DC-DC Converter

19-1462; Rev 2; 4/15

Typical Application Circuit

Pin Configuration

Ordering Information

EVALUATION KIT AVAILABLE

IN to GND ...............................................................-0.3V to +30VLX to GND ..............................................................-0.3V to +30VVL to GND ................................................................-0.3V to +6VSHDN, COMP, FB to GND ............................-0.3V to (VL + 0.3V)PGND to GND.....................................................................±0.3V

Continuous Power Dissipation (TA = +70°C) (Note 1) 16-Pin QSOP (derate 15mW/°C above +70°C)...................1W

Operating Temperature Range ...........................-40°C to +85°CJunction Temperature......................................................+150°CStorage Temperature Range .............................-65°C to +150°CSoldering Temperature (reflow) .......................................+260°C

(VIN = +6V, PGND = GND, CVL = 4.7μF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSInput Voltage VIN 3 28 V

Supply Current, No Load IIN VIN = 3V to 28V, VFB = 1.6V, SHDN = VL 500 700 µA

Supply Current, Full Load, VL Connected to IN IIN

V IN = 3V to 5.5V, VFB = 1.4V, SHDN = VL = IN

5 6.5 mA

Supply Current, Full Load IINVIN = 3.4V to 28V, VFB = 1.4V, SHDN = VL, VVL < VIN

2.5 3.5 mA

Shutdown Supply Current IIN VIN = 28V, VFB = 1.6V, SHDN = GND 3 8 µA

VL Output Voltage VVL VIN = 3.5V or 28V, no load 2.9 3.05 3.2 V

VL Load Regulation DVVL ILOAD = 0 to 2mA, VFB = 1.6V 25 40 mV

VL Undervoltage Lockout Rising edge, 1% hysteresis 2.58 2.7 2.8 V

FB Set Voltage VFB 1.47 1.5 1.53 V

FB Input Bias Current IFB VFB = 1.6V 1 50 nA

Line Regulation DVOUT VIN = 3V to 6V,VOUT = 12V 0.01 0.08 %/V

Load Regulation DVOUT VOUT = 12V, ILOAD = 10mA to 500mA 0.2 %

LX Voltage VLX 28 V

LX Switch Current Limit ILXON PWM mode 1.7 2.2 2.7 A

Idle Mode Current Limit Threshold 0.25 0.35 0.45 A

LX On-Resistance RLXON 0.3 0.6 Ω

LX Leakage Current ILXOFF VLX = 28V 0.02 10 µA

COMP Maximum Output Current ICOMP FB = GND 100 200 µA

COMP Voltage to Switch Current Transconductance DFB = 0.1V 0.8 1 mmho

SHDN Input Logic Low VIL 0.8 V

SHDN Input Logic High VIH 2.0 V

Shutdown Input Current SHDN = GND or VL 1 µA

Switching Frequency f 200 250 300 kHz

Maximum Duty Cycle DC 90 95 %


www.maximintegrated.com Maxim Integrated 2

Note 1: With part mounted on 0.9 in.2 of copper.

Absolute Maximum Ratings

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Electrical Characteristics

(VIN = +6V, PGND = GND, CVL = 4.7μF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)

Note 2: Specifications to -40°C are guaranteed by design, not production tested.

(Circuit of Figure 1, TA = +25°C.)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITSInput Voltage VIN 3 28 V

Supply Current, No Load IIN VIN = 3V to 28V, VFB = 1.6V, SHDN = VL 800 µA

Supply Current, Full Load, VL Connected to IN IIN

VIN = 3V to 5.5, VFB = 1.4V, SHDN = VL = IN

7.5 mA

Supply Current, Full Load IINVIN = 3.4V to 28V, VFB = 1.4V, SHDN = VL, VVL < VIN

4 mA

Supply Current Shutdown IIN VIN = 28V, VFB = 1.6V, SHDN = GND 10 µA

VL Output Voltage VVL VIN = 3.5V or 28V, no load 2.85 3.3 V

VL Undervoltage Lockout VVL Rising edge, 1% hysteresis 2.55 2.85 V

FB Set Voltage VFB 1.455 1.545 V

LX Voltage Range VLXON 28 V

LX Switch Current Limit ILXON PWM mode 1.4 3 A

LX On-Resistance RLXON 0.6 Ω

Switching Frequency f 188 312 kHz

100

00.1 1 10 100 1000

EFFICIENCY vs. OUTPUT CURRENT(VOUT = 12V)

20

30

10

MAX

618

toc0

1

OUTPUT CURRENT (mA)

EFFI

CIEN

CY (%

)

40

50

6070

80

90VIN = 8V

VIN = 5VVIN = 3V

100

00.1 1 10 100 1000

EFFICIENCY vs. OUTPUT CURRENT(VOUT = 28V)

20

30

10

MAX

618

toc0

2

OUTPUT CURRENT (mA)

EFFI

CIEN

CY (%

)

40

50

6070

80

90VIN = 12V

VIN = 5V

VIN = 3V

320

360

340

400

380

420

440

480

460

500

2 4 5 6 7 8 9 10 113 12

NO-LOAD SUPPLY CURRENTvs. SUPPLY VOLTAGE

MAX

618

toc0

3

SUPPLY VOLTAGE (V)

SUPP

LY C

URRE

NT (µ

A)

VOUT = 12V



Electrical Characteristics (continued)

Typical Operating Characteristics

(Circuit of Figure 1, TA = +25°C.)

0.40

0.45

0.55

0.50

0.60

0.65

0 105 15 20 25 30

NO-LOAD SUPPLY CURRENTvs. INPUT VOLTAGE

MAX

618

toc0

4

INPUT VOLTAGE (V)

SUPP

LY C

IRRE

NT (µ

A)

300

400

350

500

450

550

600

650

700

-50 -10 10-30 30 50 70 90 110

SUPPLY CURRENT vs. TEMPERATURE

MAX

618

toc0

5

TEMPERATURE (°C)

SUPP

LY C

URRE

NT (µ

A)

VIN = 8V

VIN = 5V

VIN = 3V

INCLUDES CAPACITOR LEAKAGE CURRENT0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

2 127 17 22 27 32

SHUTDOWN CURRENTvs. SUPPLY VOLTAGE

MAX

618

toc0

6

SUPPLY VOLTAGE (V)

SHUT

DOW

N CU

RREN

T (µ

A)

0

VOUT(100mV/div)

VLX(10V/div)

IL(1A/div)

MEDIUM-LOAD SWITCHINGWAVEFORMS

MAX618 toc07

VIN = 5V, VOUT = 12V, IOUT = 200mA

2µs/div

0

VOUT(100mV/

div)

VLX(10V/div)

IL(1A/div)

HEAVY-LOAD SWITCHINGWAVEFORMS

MAX618 toc08

VIN = 5V, VOUT = 12V, IOUT = 500mA

2µs/div

3V6V

VOUT(50mV/div)

VIN(5V/div)

LINE-TRANSIENT RESPONSEMAX618 toc09

IOUT = 200mA, VOUT = 12V

2ms/div

0

VOUT(200mV/div)

IOUT(100mA/div)

LOAD-TRANSIENT RESPONSEMAX618 toc10

VIN = 5V, VOUT = 12V

5ms/div

5V

12V

0

SHDN(2V/div)

VOUT(2V/div)

SHUTDOWN RESPONSEMAX618 toc11

VIN = 5V, VOUT = 12V, ILOAD = 500mA

500µs/div0

0.4

0.2

0.6

1.2

1.4

1.0

0.8

1.6

2 4 5 6 73 8 9 10 11 12

MAXIMUM OUTPUT CURRENTvs. INPUT VOLTAGE

MAX

618

toc1

2

INPUT VOLTAGE (V)

MAXI

MUM

OUTP

UT C

URRE

NT (A

)

VOUT = 12V


Maxim Integrated 4www.maximintegrated.com

Typical Operating Characteristics (continued)

Figure 1. Single-Supply Operation

PIN NAME FUNCTION1, 8, 9, 12, 16 GND Ground

2, 3, 4 LX Drain of Internal n-channel Switch. Connect the inductor between IN and LX.

5 SHDNShutdown Input. A logic low puts the MAX618 in shutdown mode and reduces supply current to 3µA. SHDN must not exceed VL. In shutdown, the output falls to VIN less one diode drop.

6 COMP Compensation Input. Bypass to GND with the value of capacitance shown in Table 2.

7 FB Feedback Input. Connect a resistor-divider network to set VOUT. FB threshold is 1.5V.

10 IN LDO Regulator Supply Input. IN accepts inputs up to +28V. Bypass to GND with a 1µF ceramic capacitor as close to pins 10 and 12 as possible.

11 VL Internal 3.1V LDO Regulator Output. Bypass to GND with a 4.7µF capacitor.

13, 14, 15 PGND Power Ground. Source of internal N-channel switch.

COMP 2

+5V INPUT

R3169kΩ

R4100kΩ

L1470

LOW BATTERY INPUT

1.31V

OSC

RON AT 3Ω

40kHz COMP 1

1.31V

BANDGAPREFERENCE

ANDBIAS GENERATOR

1 LBR

2 CX

3 LX

4 GND

D11N4148

+VS 5

IC 6

VFB 7

LBD 8 LOW-BATTERY OUTPUT(LOW IF INPUT < 3V)

CC

R1499kΩ

R247.5kΩ

SHUTDOWN

OPERATE

+15V OUTPUT20mA

C1470mF25V

MAX618

COMP 2



Pin Description

Detailed DescriptionThe MAX618 pulse-width modulation (PWM) DC-DC converter with an internal 28V switch operates in a wide range of DC-DC conversion applications including boost, SEPIC, and flyback configurations. The MAX618 uses fixed-frequency PWM operation and Maxim’s proprietary Idle Mode control to optimize efficiency over a wide range of loads. It also features a shutdown mode to minimize quiescent current when not in operation.

PWM Control Scheme and Idle Mode OperationThe MAX618 combines continuous-conduction PWM operation at medium to high loads and Idle Mode opera-tion at light loads to provide high efficiency over a wide

range of load conditions. The MAX618 control scheme actively monitors the output current and automatically switches between PWM and Idle Mode to optimize efficiency and load regulation. Figure 2 shows a functional diagram of the MAX618’s control scheme.The MAX618 normally operates in low-noise, continuous- conduction PWM mode, switching at 250kHz. In PWM mode, the internal MOSFET switch turns on with each clock pulse. It remains on until either the error comparator trips or the inductor current reaches the 2A switch-current limit. The error comparator compares the feedback-error signal, current-sense signal, and slope-compensation signal in one circuit block. When the switch turns off, energy transfers from the inductor to the output capacitor. Output current is limited by the 2A MOSFET current limit

Figure 2. Functional Diagram

SHDN

MAX618

IDLE MODECURRENT LIMIT

PWMCURRENT LIMIT

ERRORCOMPARATOR

250kHzOSCILLATOR

SLOPECOMPENSATION

LINEARREGULATOR

CURRENT-SENSE

CIRCUIT

PGND IN

LX OUTR

14R

VL

FB

COMP

IN

VL

NMOS

REFERENCE

INTEGRATOR

GND

SHUTDOWN

PWMLOGIC

THERMALSHUTDOWN



and the MAX618’s package power-dissipation limit. See the Maximum Output Current section for details.In Idle Mode, the MAX618 improves light-load efficiency by reducing inductor current and skipping cycles to reduce the losses in the internal switch, diode, and inductor. In this mode, a switching cycle initiates only when the error comparator senses that the output voltage is about to drop out of regulation. When this occurs, the NMOS switch turns on and remains on until the inductor current exceeds the nominal 350mA Idle Mode current limit.Refer to Table 1 for an estimate of load currents at which the MAX618 transitions between PWM and Idle Mode.

Compensation SchemeAlthough the higher loop gain of voltage-controlled architectures tends to provide tighter load regulation, current-controlled architectures are generally easier to compensate over wide input and output voltage ranges. The MAX618 uses both control schemes in parallel: the dominant, low-frequency components of the error signal are tightly regulated with a voltage-control loop, while a current-control loop improves stability at higher

frequencies. Compensation is achieved through the selection of the output capacitor (COUT), the integrator capacitor (CCOMP), and the pole capacitor (CP) from FB to GND. CP cancels the zero formed by COUT and its ESR. Refer to the Capacitor Selection section for guidance on selecting these capacitors.

VL Low-Dropout RegulatorThe MAX618 contains a 3.1V low-dropout linear regulator to power internal circuitry. The regulator’s input is IN and its output is VL. The IN to VL dropout voltage is 100mV, so that when IN is less than 3.2V, VL is typically 100mV below IN. The MAX618 still operates when the LDO is in dropout, as long as VL remains above the 2.7V undervolt-age lockout. Bypass VL with a 4.7μF ceramic capacitor placed as close to the VL and GND pins as possible.VL can be overdriven by an external supply between 2.7V and 5.5V. In systems with +3.3V or +5V logic power supplies available, improve efficiency by powering VL and VIN directly from the logic supply as shown in Figure 3.



Tabl

e 1.

PW

M/Id

le-M

ode

Tran

sitio

n Lo

ad C

urre

nt (I

OU

T in

Am

ps) v

s. In

put a

nd O

utpu

t Vol

tage

V IN

V OU

T4

56

78

910

1112

1314

1516

1718

1920

2122

2324

2526

2728

30.

200.

200.

180.

150.

120.

100.

090.

080.

070.

060.

050.

040.

040.

040.

030.

030.

030.

030.

030.

020.

020.

020.

020.

020.

02

40.

180.

210.

200.

170.

150.

130.

120.

100.

090.

080.

070.

070.

060.

050.

050.

040.

040.

040.

030.

030.

030.

030.

030.

03

50.

160.

200.

210.

190.

170.

160.

140.

130.

110.

100.

090.

090.

080.

070.

070.

060.

060.

050.

050.

040.

040.

040.

04

60.

150.

200.

210.

200.

190.

180.

160.

150.

130.

120.

110.

100.

100.

090.

080.

080.

070.

070.

060.

060.

050.

05

70.

170.

190.

210.

210.

200.

190.

170.

160.

150.

140.

130.

120.

110.

100.

100.

090.

080.

080.

070.

070.

07

80.

190.

180.

200.

210.

200.

200.

190.

170.

160.

150.

140.

130.

130.

120.

110.

100.

100.

090.

090.

08

90.

200.

170.

200.

210.

210.

200.

190.

180.

180.

170.

160.

150.

140.

130.

120.

120.

110.

100.

10

100.

210.

160.

190.

200.

210.

210.

200.

190.

180.

170.

170.

160.

150.

140.

130.

130.

120.

11

110.

220.

150.

190.

200.

210.

210.

200.

200.

190.

180.

170.

170.

160.

150.

140.

140.

13

120.

230.

150.

180.

200.

210.

210.

210.

200.

200.

190.

180.

180.

170.

160.

150.

15

130.

240.

160.

170.

190.

200.

210.

210.

200.

200.

190.

190.

180.

170.

170.

16

140.

250.

170.

170.

190.

200.

210.

210.

210.

200.

200.

190.

190.

180.

17

150.

250.

180.

160.

180.

200.

200.

210.

210.

210.

200.

200.

190.

19

160.

260.

190.

160.

180.

190.

200.

210.

210.

210.

200.

200.

20

170.

260.

200.

150.

170.

190.

200.

200.

210.

210.

210.

20

180.

270.

200.

150.

170.

190.

200.

200.

210.

210.

21

190.

270.

210.

160.

170.

180.

190.

200.

210.

21

200.

270.

210.

170.

160.

180.

190.

200.

20

210.

280.

220.

170.

160.

180.

190.

20

220.

280.

220.

180.

150.

170.

19

230.

280.

230.

180.

150.

17

240.

280.

230.

190.

15

250.

290.

240.

19

260.

290.

24

270.

29



Operating ConfigurationsThe MAX618 can be connected in one of three configura-tions described in Table 2 and shown in Figures 1, 3, and 4. The VL linear regulator allows operation from a single supply between +3V and +28V as shown in Figure 1.The circuit in Figure 3 allows a logic supply to power the MAX618 while using a separate source for DC-DC

conversion power (inductor voltage). The logic supply (between 2.7V and 5.5V) connects to VL and IN. VL = IN; voltages of 3.3V or more improve efficiency by providing greater gate drive for the internal MOSFET.The circuit in Figure 4 allows separate supplies to power IN and the inductor voltage. It differs from the connection in Figure 3 in that the MAX618 chip supply is not limited to 5.5V.

Figure 3. Dual-Supply Operation (VIN = 2.7V to 5.5V) Figure 4. Dual-Supply Operation (VIN = 3V to 28V)

Table 2. Input Configurations

CIRCUIT CONNECTION VIN RANGE INDUCTOR VOLTAGE BENEFITS/COMMENTS

Figure 1Input voltage connects to IN and inductor.

3V to VOUT (up to 28V) VIN

• Single supply operation. • SHDN must be connected to or pulled up to VL. On/off control

requires an open-drain or open-collector connection to SHDN.

Figure 3

IN and VL connect together. Inductor voltage supplied by a separate source.

2.7V to 5.5V 0V to VOUT (up to 28V)

• Increased efficiency.• SHDN can be driven by logic powered from the supply

connected to IN and VL, or can be connected to or pulled up to VL.

• Input power source (inductor voltage) is separate from the MAX618’s bias (VIN = VL) and can be less than or greater than VIN.

Figure 4

IN and inductor voltage supplied by separate sources.

3V to 28V 0V to VOUT (up to 28V)

• Input power source (inductor voltage) is separate from the MAX618’s bias (VIN) and can be less than or greater than VIN.

• SHDN must be connected to or pulled up to VL. On/off control requires an open-drain or open-collector connection to SHDN.

GND

LX

COUT

L

PGND

R2

R1

CP

VL

COMPCCOMP

IN

SHDN

UP TO 28V

VINDUP TO 28V

CIND

IN OUT

MAX618

2.7V TO 5.5V

4.7µF

1µF

FB

LX

CIND

COUT

L

PGND

GND

R1

VL

COMPCCOMP

IN

SHDN

UP TO 28V

VINDUP TO 28V

OUT

MAX618

IN3V TO 28V

4.7µF

1µF

R2CP

FB



Shutdown ModeIn shutdown mode (SHDN = 0), the MAX618’s feedback and control circuit, reference, and internal biasing circuitry turn off and reduce the IN supply current to 3μA (10μA max). When in shutdown, a current path remains from the input to the output through the external inductor and diode. Consequently, the output falls to VIN less one diode drop in shutdown.SHDN may not exceed VL. For always-on operation, connect SHDN to VL. To add on/off control to the circuit of Figure 1 or 4, pull SHDN to VL with a resistor (10kΩ to 100kΩ) and drive SHDN with an open-drain logic gate or switch as shown in Figure 5. Alternatively, the circuit of Figure 3 allows direct SHDN drive by any logic-level gate powered from the same supply that powers VL and IN, as shown in Figure 6.

Design ProcedureThe MAX618 operates in a number of DC-DC converter configurations including step-up, SEPIC, and flyback. The following design discussion is limited to step-up converters.

Setting the Output VoltageTwo external resistors (R1 and R2) set the output voltage. First, select a value for R2 between 10kΩ and 200kΩ. Calculate R1 with:

OUT1 2

FB

VR R 1V

= −

where VFB is 1.5V.

Determining the Inductor ValueThe MAX618’s high switching frequency allows the use of a small value inductor. The recommended inductor value is proportional to the output voltage and is given by the following:

OUT5

VL7 10

=×

After solving for the above equation, round down as necessary to select a standard inductor value. When selecting an inductor, choose one rated to 250kHz, with a saturation current exceeding the peak inductor current, and with a DC resistance under 200mΩ. Ferrite core or equivalent inductors are generally appropriate (see MAX618 EV kit data sheet). Calculate the peak inductor current with the following equation:

( )OUT INOUT INLX(PEAK) OUT

IN OUT

V VV VI I 2µsV L V

− = +

Note that the peak inductor current is internally limited to 2A.

Diode SelectionThe MAX618’s high switching frequency demands a high-speed rectifier. Schottky diodes are preferred for most applications because of their fast recovery time and low forward voltage. Make sure that the diode’s peak current rating exceeds the 2A peak switch current, and that its breakdown voltage exceeds the output voltage.

Figure 5. Adding On/Off Control to Circuit of Figure 1 or 4 Figure 6. Adding On/Off Control to Circuit of Figure 3

MAX618

VL

100kΩ

ON/OFF CONTROL

OPEN-DRAINLOGIC

SHDN

MAX618

IN

VL

SYSTEM LOGIC

ON/OFFCONTROL

SHDN

SYSTEMLOGIC SUPPLY



Maximum Output CurrentThe MAX618’s 2.2A LX current limit determines the output power that can be supplied for most applications. In some cases, particularly when the input voltage is low, output power is sometimes restricted by package dissipation limits. The MAX618 is protected by a thermal shutdown circuit that turns off the switch when the die temperature exceeds +150°C. When the device cools by 10°C, the switch is enabled again. Table 3 details output current with a variety of input and output voltages. Each listing in Table 3 is either the limit set by an LX current limit or by package dissipation at +85°C ambient, whichever is lower. The values in Table 3 assume a 40mΩ inductor resistance.

Capacitor SelectionInput CapacitorsThe input bypass capacitor (CIND) reduces the input ripple created by the boost configuration. High-impedance sources require high CIND values. However, 68μF is generally adequate for input currents up to 2A. Low-ESR capacitors are recommended because they will decrease the ripple created on the input and improve efficiency. Capacitors with ESR below 0.3Ω are generally appropriate.In addition to the input bypass capacitor, bypass IN with a 1μF ceramic capacitor placed as close to the IN and GND pins as possible. Bypass VL with a 4.7μF ceramic capaci-tor placed as close to the VL and GND pins as possible.

Output CapacitorUse Table 4 to find the minimum output capacitance necessary to ensure stable operation. In addition, choose an output capacitor with low ESR to reduce the output ripple. The dominant component of output ripple is the product of the peak-to-peak inductor ripple current and the ESR of the output capacitor. ESR below 50mΩ generates acceptable levels of output ripple for most applications.

Integrator CapacitorThe compensation capacitor (CCOMP) sets the dominant pole in the MAX618’s transfer function. The proper com-pensation capacitance depends upon output capacitance. Table 5 shows the capacitance value needed for the output capacitances specified in Table 4. However, if a

different output capacitor is used (e.g., a standard value), then recalculate the value of capacitance needed for the integrator capacitor with the following formula:

COMP OUTCOMP

OUT

C (Table 5) CCC (Table 4)

×=

Pole Compensation CapacitorThe pole capacitor (CP) cancels the unwanted zero intro-duced by COUT’s ESR, and thereby ensures stability in PWM operation. The exact value of the pole capacitor is not critical, but it should be near the value calculated by the following equation:

ESR OUT 1 2P

1 2

R C (R R )CR R

× +=

×

where RESR is COUT’s ESR.

Layout ConsiderationsProper PC board layout is essential due to high current levels and fast switching waveforms that radiate noise. Use the MAX618 evaluation kit or equivalent PC layout to perform initial prototyping. Breadboards, wire-wrap, and proto-boards are not recommended when prototyping switching regulators.It is important to connect the GND pin, the input bypass capacitor ground lead, and the output filter capacitor ground lead to a single point to minimize ground noise and improve regulation. Also, minimize lead lengths to reduce stray capacitance, trace resistance, and radiated noise, with preference given to the feedback circuit, the ground circuit, and LX. Place the feedback resistors as close to the FB pin as possible. Place a 1μF input bypass capacitor as close as possible to IN and GND.Refer to the MAX618 evaluation kit for an example of proper board layout.

PACKAGE TYPE PACKAGE CODE DOCUMENT NO.16 QSOP EF16+8F 21-0055



Package InformationFor the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.

Chip InformationPROCESS: BiCMOS

http://pdfserv.maximintegrated.com/package_dwgs/21-0055.PDF

Tabl

e 3.

Typ

ical

Out

put C

urre

nt v

s. In

put a

nd O

utpu

t Vol

tage

s

V IN

V OU

T4

56

78

910

1112

1314

1516

1718

1920

2122

2324

2526

2728

30.

770.

590.

490.

410.

340.

290.

250.

220.

200.

180.

170.

150.

140.

130.

120.

120.

110.

100.

100.

090.

090.

080.

080.

080.

074

0.96

0.76

0.64

0.56

0.49

0.43

0.38

0.34

0.31

0.28

0.26

0.24

0.22

0.21

0.19

0.18

0.17

0.16

0.16

0.15

0.14

0.14

0.13

0.12

51.

090.

890.

760.

670.

600.

540.

500.

450.

410.

370.

340.

320.

300.

280.

260.

250.

230.

220.

210.

200.

190.

180.

186

1.18

0.99

0.85

0.76

0.68

0.63

0.58

0.54

0.50

0.46

0.42

0.39

0.37

0.34

0.32

0.31

0.29

0.28

0.26

0.25

0.24

0.23

71.

261.

070.

930.

830.

760.

700.

650.

600.

570.

530.

500.

460.

430.

410.

380.

360.

350.

330.

310.

300.

298

1.32

1.13

1.00

0.90

0.82

0.76

0.71

0.66

0.62

0.59

0.56

0.53

0.50

0.47

0.44

0.42

0.40

0.38

0.36

0.35

91.

371.

191.

060.

960.

880.

810.

760.

710.

670.

640.

610.

580.

550.

530.

500.

470.

450.

430.

4110

1.41

1.24

1.11

1.01

0.93

0.86

0.81

0.76

0.72

0.68

0.65

0.62

0.59

0.57

0.55

0.52

0.50

0.47

111.

441.

281.

151.

050.

970.

910.

850.

800.

760.

720.

690.

660.

630.

610.

580.

560.

5412

1.47

1.31

1.19

1.10

1.02

0.95

0.89

0.84

0.80

0.76

0.73

0.70

0.67

0.64

0.62

0.60

131.

491.

341.

231.

131.

050.

990.

930.

880.

830.

800.

760.

730.

700.

670.

6514

1.52

1.37

1.26

1.16

1.09

1.02

0.96

0.91

0.87

0.83

0.79

0.76

0.73

0.71

151.

531.

401.

291.

191.

121.

050.

990.

940.

900.

860.

820.

790.

7616

1.55

1.42

1.31

1.22

1.14

1.08

1.02

0.97

0.93

0.89

0.85

0.82

171.

571.

441.

331.

251.

171.

111.

051.

000.

950.

910.

8818

1.58

1.46

1.36

1.27

1.20

1.13

1.07

1.02

0.98

0.94

191.

591.

471.

371.

291.

221.

151.

101.

051.

0020

1.60

1.49

1.39

1.31

1.24

1.18

1.12

1.07

211.

611.

501.

411.

331.

261.

201.

1422

1.62

1.51

1.42

1.35

1.28

1.22

231.

631.

531.

441.

361.

2924

1.64

1.54

1.45

1.38

251.

641.

551.

4626

1.65

1.56

271.

66



Tabl

e 4.

Min

imum

CO

UT

for S

tabi

lity

(μF)

V IN

V OU

T4

56

78

910

1112

1314

1516

1718

1920

2122

2324

2526

2728

317

312

810

080

6554

4640

3531

2825

2321

1918

1715

1514

1312

1211

10

415

111

896

8068

5951

4539

3532

2927

2423

2120

1817

1615

1514

13

513

210

790

7767

5952

4641

3734

3129

2625

2321

2019

1817

1615

611

797

8372

6457

5146

4238

3532

3028

2624

2321

2019

1817

710

489

7768

6155

5045

4239

3533

3028

2625

2322

2120

19

894

8272

6458

5248

4441

3835

3331

2927

2524

2221

20

986

7667

6155

5046

4239

3734

3230

2927

2524

2321

1079

7063

5752

4844

4138

3634

3230

2827

2524

23

1173

6659

5450

4643

4037

3533

3129

2826

2524

1268

6256

5147

4441

3836

3432

3029

2726

25

1364

5853

4945

4239

3735

3331

2928

2725

1460

5550

4743

4038

3634

3230

2927

26

1556

5248

4442

3937

3533

3129

2827

1653

4946

4340

3735

3332

3029

27

1750

4744

4138

3634

3231

2928

1848

4542

3937

3533

3130

28

1946

4340

3836

3432

3029

2043

4138

3634

3331

29

2142

3937

3533

3230

2240

3836

3432

31

2338

3634

3331

2437

3533

32

2535

3432

2634

33

2733



Tabl

e 5.

Min

imum

CC

OM

P fo

r Sta

bilit

y (n

F)

V IN

V OU

T4

56

78

910

1112

1314

1516

1718

1920

2122

2324

2526

2728

340

4654

6473

8394

105

118

130

143

157

172

187

203

219

236

253

271

290

309

329

349

370

391

442

4551

5866

7482

9110

010

911

913

014

115

216

417

618

820

121

422

824

225

727

228

7

543

4549

5460

6775

8188

9610

311

112

012

813

714

715

616

617

618

719

720

922

0

644

4548

5257

6268

7480

8692

9910

511

211

912

713

414

215

015

916

717

6

745

4547

5054

5863

6874

7985

9095

101

107

113

119

125

132

139

146

846

4547

4952

5660

6468

7378

8388

9398

103

108

113

119

124

946

4647

4851

5457

6164

6873

7782

8691

9599

104

109

1047

4646

4850

5255

5861

6569

7277

8185

8993

97

1147

4646

4849

5154

5659

6265

6972

7680

8488

1248

4747

4749

5052

5557

6063

6669

7275

79

1348

4747

4748

5052

5456

5861

6366

6972

1449

4747

4748

4951

5355

5759

6164

66

1549

4747

4748

4950

5253

5557

5962

1649

4847

4748

4950

5153

5456

58

1749

4847

4748

4849

5152

5355

1850

4847

4748

4849

5051

53

1950

4847

4748

4849

5051

2050

4848

4748

4849

49

2150

4948

4748

4848

2250

4948

4848

48

2350

4948

4848

2451

4948

48

2551

4948

2651

49

2751



REVISION NUMBER

REVISION DATE DESCRIPTION PAGES

CHANGED0 6/09 Initial release —

1 12/09 Updated part to lead-free, added soldering temperatures (reflow), and corrected error in equation 1, 2, 10

2 4/15 No /V ordering information; removed Automotive reference from Applications section 1

Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.

Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.


© 2015 Maxim Integrated Products, Inc. 15

Revision History

For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.

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