MAX8655(2007) Просмотр технического описания (PDF) - Maxim Integrated

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MAX8655
(Rev.:2007)

Highly Integrated, 25A, Wide-Input, Internal MOSFET, Step-Down Regulator

Maxim Integrated 

Highly Integrated, 25A, Wide-Input,

Internal MOSFET, Step-Down Regulator

PIN

1–5, 51–56

6, 16–21

7–15

22

23, 28, 39,

48

24

25

26

27

29, 30, 42, 49

31

32

33

34

35

36

37

38

NAME

PVIN

LX

PGND

VLGND

GND

VL

IN

EN

AVL

N.C.

CS+

CS-

ILIM1

OVP

FB

COMP

SS

REFIN

Pin Description

FUNCTION

Power-Input Supply. PVIN connects to the drain of the internal high-side MOSFET. Connect input-

decoupling capacitors as close as possible between PVIN and PGND.

External Inductor Connection. Connect to the external power inductor. Leave pin 6 unconnected for

best routing.

Power Ground Connection from Source of Internal Low-Side MOSFET. Connect input-decoupling

capacitors as close as possible between PVIN and PGND.

Return for Low-Side MOSFET Gate-Driver Current

Analog Ground. Connect all pins to the analog ground plane, and connect the analog and power

ground planes together at the negative terminal of the output capacitor. Low-current signals return to

GND. Pin 28 must be connected externally to GND-EP, the analog ground plane.

Internal 6.5V Linear-Regulator Output. Connect a 2.2µF to 10µF ceramic capacitor from VL to VLGND.

For VIN < 7V, connect VL directly to IN. VL supplies power for the internal gate drivers. VL is the input

to the AVL internal linear regulator.

Input Supply Voltage. IN is the input to the VL linear regulator. Connect VL to IN for VIN < 7V.

Decouple to PGND with a 0.22µF ceramic capacitor.

Enable. Apply logic-high to EN to enable the output, or logic-low to place the regulator in low-power

shutdown mode. Connect EN to IN for always-on operation.

Internal 5V Linear-Regulator Output. AVL powers the MAX8655’s internal circuits. Connect a 1µF

ceramic capacitor from AVL to GND.

No Connection. Not internally connected.

Positive Differential Current-Sense Input

Negative Differential Current-Sense Input

Analog Programmable Current-Limit Input for Inductor Current. Connect a resistor from ILIM1 to GND

to set the overcurrent threshold. ILIM1 sources 10µA through the resistor, and the voltage at ILIM1 is

attenuated 7.5:1 to set the final current limit. For example, a 60kΩ resistor results in 600mV at ILIM1.

This results in a current-limit threshold (VCS+ - VCS-) of 80mV. The ILIM1 resistor range is 24kΩ to

60kΩ. Connect ILIM1 to AVL to set the default threshold of 80mV.

Output-Voltage Sensing for Overvoltage Protection. Connect OVP to the center of a resistor-divider

connected between the output of the regulator and GND to set the FB independent output

overvoltage trip point. Connect OVP to FB if this independence is not desired. The OVP threshold is

1.15 times the nominal feedback regulation voltage.

Feedback Input. Connect FB to the center of a resistor voltage-divider connected between the output

and GND to set the output voltage. FB regulates to 0.7V or VREFIN.

Loop Compensation. Connect COMP to an external RC network to compensate the loop. COMP is

internally pulled to GND through 20Ω during shutdown.

Soft-Start. Connect a 0.01µF to 1µF ceramic capacitor from SS to GND. This capacitor sets the soft-

start period during startup. See the Startup and Soft-Start section for more details. SS is internally

pulled to GND through 20Ω during shutdown.

External Reference Input. Connect REFIN to AVL to use the internal 0.7V reference for the feedback

threshold.

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