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MAX1887

Quick-PWM Slave Controllers for Multiphase, Step-Down Supplies

Maxim Integrated 

Quick-PWM Slave Controllers for

Multiphase, Step-Down Supplies

PIN

MAX1887 MAX1897

1

19

2

20

3

1

4

2

—

3

5

4

6

5

7

6

—

7

8

8

9

9

10

10

11

11

—

12

—

13

NAME

ILIM

TRIG

CM+

CM-

TON

CS-

CS+

COMP

POL

GND

PGND

DL

VDD

VCC

SHDN

Pin Description

DESCRIPTION

Dual-Mode Current-Limit Adjustment and Standby Input. The current-limit threshold

voltage is 1/10 the voltage seen at ILIM (VILIM) over a 400mV to 1.5V range. If VILIM

drops below 250mV, the slave controller enters a low-power standby mode, forcing

DL high and DH low.

Trigger Input. Connect to the master controller’s low-side gate driver. For the

MAX1887, a rising edge triggers a single cycle. For the MAX1897, the trigger input’s

polarity is pin selectable. POL = VCC or floating triggers on the rising edge (out-of-

phase operation), and POL = GND triggers on the falling edge (in-phase operation).

Master Controller’s Positive Current-Sense Input

Master Controller’s Negative Current-Sense Input

On-Time Selection Control Input. This is a three-level input used to determine the DH

on time (see On-Time Control and Active Current Balancing). For the MAX1897,

connect TON as follows for the indicated switching frequencies:

GND = 550kHz

floating = 300kHz

VCC = 200kHz.

For the MAX1887, the switching frequency is internally configured for 300kHz

operation. The slave controller’s switching frequency should be selected to closely

match the frequency of the master PWM controller.

Slave Controller’s Negative Current-Sense Input

Slave Controller’s Positive Current-Sense Input

Current Balance Compensation. Connect a series resistor and capacitor between

COMP and OUT. See the Current Balance Compensation section.

TRIG Polarity Select Input. Connect POL to VCC or float to trigger on the rising edge of

TRIG (out-of-phase operation). Connect POL to GND to trigger on the falling edge of TRIG

(in-phase operation). For the MAX1887, POL is internally connected to VCC.

Analog Ground. Connect the MAX1897’s exposed pad to analog ground.

Power Ground

Low-Side Gate-Driver Output. DL swings from PGND to VDD. DL is forced high

when the MAX1897 enters standby or shutdown mode.

Supply Voltage Input for the DL Gate Driver. For the MAX1887, VDD also serves as

the analog supply voltage input that powers the PWM core. Connect to the system

supply voltage (4.5V to 5.5V). Bypass to PGND with a 1µF or greater ceramic

capacitor, as close to the IC as possible.

Analog Supply Voltage Input for PWM Core. Connect VCC to the system supply

voltage (4.5V to 5.5V) through a series 10Ω resistor. Bypass to GND with a 0.22µF

or greater ceramic capacitor, as close to the MAX1897 as possible.

Active-Low Shutdown Input. A logic low shuts down the MAX1897 slave controller,

immediately pulling DL high and DH low. Connect to VCC for normal operation.

10 ______________________________________________________________________________________

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