MAX1639 Datasheet, PDF(5/13 Page) Maxim Integrated Products – High-Speed Step-Down Controller with Synchronous Rectification for CPU Power

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MAX1639 Datasheet, PDF (5/13 Pages) Maxim Integrated Products – High-Speed Step-Down Controller with Synchronous Rectification for CPU Power

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High-Speed Step-Down Controller with

Synchronous Rectification for CPU Power

______________________________________________________________Pin Description

NAME

FUNCTION

BST

Boost-Capacitor Bypass for High-Side MOSFET Gate Drive. Connect a 0.1ÂµF capacitor and low-leak-

age Schottky diode as a bootstrapped charge-pump circuit to derive a 5V gate drive from VDD for DH.

PWROK

Open-Drain Logic Output. PWROK is high when the voltage on FB is within +8% and -6% of its set-

point.

CSL

Current-Sense Amplifierâs Inverting Input. Place the current-sense resistor very close to the controller IC,

and use a Kelvin connection.

CSH

Current-Sense Amplifierâs Noninverting Input

VCC

Analog Supply Input, 5V. Use an RC filter network, as shown in Figure 1.

REF

Reference Output, 3.5V. Bypass REF to AGND with 0.1ÂµF (min). Sources up to 100ÂµA for external

loads. Force REF below 2V to turn off the controller.

AGND Analog Ground

Voltage-Feedback Input. The voltage at this input is regulated to 1.100V.

CC1

Fast-Loop Compensation Capacitor Input. Connect a ceramic capacitor and resistor in series from

CC1 to AGND. See the section Compensating the Feedback Loop.

CC2

Slow-Loop Compensation Capacitor Input. Connect a ceramic capacitor from CC2 to AGND. See the

section Compensating the Feedback Loop.

Frequency-Select Input. FREQ = VCC: 1MHz

FREQ

FREQ = REF: 600kHz

FREQ = AGND: 300kHz

VDD

Power Input for MOSFET Drivers, 5V. Bypass VDD to PGND within 0.2 in. (5mm) of the VDD pin using a

0.1ÂµF capacitor and 4.7ÂµF capacitor connected in parallel.

Low-Side Synchronous Rectifier Gate-Drive Output. DL swings between PGND and VDD. See the

section BST High-Side Gate-Driver Supply and MOSFET Drivers.

PGND Power Ground

Switching Node. Connect LX to the high-side MOSFET source and inductor.

High-Side Main MOSFET Switch Gate-Drive Output. DH is a floating driver output that swings from LX

to BST, riding on the LX switching-node voltage. See the section BST High-Side Gate-Driver Supply

and MOSFET Drivers.

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