MP28372 — DUAL 1.5A, 23V, 1.4MHz STEP-DOWN CONVERTER

MP28372 Rev. 1.4

www.MonolithicPower.com

4

12/10/2007

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TM

PIN FUNCTIONS (TSSOP20F)

Pin #

Name

Description

1

SSA

Soft-Start Control for Channel A. 9kΩ output resistance from the pin. Set RC time constant

with external capacitor for soft start ramp time. Ramp Time = 2.2 x 9kΩ x C.

2

NC

No Connect

3

BSA

High-Side Driver Boost Pin. Connect a 10nF capacitor from this pin to SWA.

4

INA

Supply Voltage Channel A. The MP28372 operates from a +4.75V to +23V unregulated input.

Input Ceramic Capacitors should be close to this pin.

5

SWA

Switch Channel A. This connects the inductor to either INA through M1A or to PGA through M2A.

6

PGA

Power Ground Channel A. This is the Power Ground Connection to the input capacitor

ground.

7

SGA

Signal Ground Channel A. This pin is the signal ground reference for the regulated output

voltage. For this reason care must be taken in its layout. This node should be placed outside

of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise

into the part.

8

FBB

Feedback Voltage for Channel B. This pin is the feedback voltage. The output voltage is ratio scaled

through a voltage divider, and the center point of the divider is connected to this pin. The voltage is

compared to the on board 0.92V reference.

9

COMPB

Compensation Channel B. This is the output of the transconductance error amplifier. A series

RC is placed on this pin for proper control loop compensation. Please refer to more in the

datasheet.

10

ENB

Enable/UVLO Channel B. A voltage greater than 2.62V enables operation. Leave ENB

unconnected for automatic startup. An Under Voltage Lockout (UVLO) function can be

shutdown the ENB pin voltage needs to be less than 700mV.

11

SSB

Soft-Start Control for Channel B. 9kΩ output resistance from the pin. Set RC time constant

with external capacitor for soft start ramp time. Ramp Time = 2.2x9kΩxC.

12

BSB

High-Side Driver Boost Pin. Connect a 10nF capacitor from this pin to SWB.

13

NC

No Connect.

14

INB

Supply Voltage Channel B. The MP28372 operates from a +4.75V to +23V unregulated input.

Input Ceramic Capacitors should be close to this pin.

15

SWB

Switch Channel B. This connects the inductor to either INB through M1B or to PGB through M2B.

16

PGB

Power Ground Channel B. This is the Power Ground Connection to the input capacitor

ground.

17

SGB

Signal Ground Channel B. This pin is the signal ground reference for the regulated output

voltage. For this reason care must be taken in its layout. This node should be placed outside

of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise

into the part.

18

FBA

Feedback Voltage for Channel A. This pin is the feedback voltage. The output voltage is ratio scaled

through a voltage divider, and the center point of the divider is connected to this pin. The voltage is

compared to the on board 0.92V reference.

19

COMPA

Compensation Channel A. This is the output of the transconductance error amplifier. A series

RC is placed on this pin for proper control loop compensation. Please refer to more in the

datasheet.

20

ENA

Enable/UVLO Channel A. A voltage greater than 2.62V enables operation. Leave ENA

unconnected for automatic startup. An Under Voltage Lockout (UVLO) function can be

shutdown the ENA pin voltage needs to be less than 700mV.