MAX1636(1997) データシートの表示（PDF） - Maxim Integrated

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MAX1636
(Rev.:1997)

Low-Voltage, Precision Step-Down Controller for Portable CPU Power

Maxim Integrated 

Low-Voltage, Precision Step-Down

Controller for Portable CPU Power

______________________________________________________________Pin Description

PIN

1

2

3

4

5

6

7

8

9, 10

11

12

13

14

15

16

17

18

19

20

NAME

CSH

CSL

RESET

SHDN

OVP

CC

REF

SYNC

GND

FB

VCC

V+

VL

DL

PGND

BST

DH

LX

SKIP

FUNCTION

Current-Sense Input, High Side

Current-Sense Input, Low Side. Also serves as a feedback input in fixed output modes.

Timed Reset Output. Low for at least 100ms after output voltage is valid, then goes high impedance

(open drain).

Shutdown Control Input. Puts chip in shutdown or standby mode, depending on OVP (Table 5).

Overvoltage Protection Enable/Disable. Tie to GND to disable OVP; tie to VCC to enable OVP.

Compensation pin. Connect a small capacitor to GND to set the integration time constant.

1.100V Reference Output. Capable of sourcing 50µA for external loads; bypass with a 0.22µF

(min) capacitor.

Oscillator Frequency Select and Synchronization Input. Tie to VCC for 300kHz operation; tie to GND for

200kHz operation.

Analog Ground

Feedback Input. Tie to GND for fixed 3.3V output; tie to VCC for fixed 2.5V output; tie to resistor divider for

adjustable mode.

Main Supply Voltage Input. Powers the PWM controller, logic, and reference. Input range is +3.15V to

+5.5V.

5V VL Linear-Regulator Input. The VL linear regulator automatically shuts off if V+ is left open or shorted to

VL. Bypass V+ to GND with a 0.1µF capacitor close to the IC.

5V Linear-Regulator Output. Powers the DL low-side gate driver. Bypass with a 2.2µF (min) capacitor.

Low-Side Gate-Driver Output

Power Ground

Boost-Capacitor Connection

High-Side Gate-Driver Output

Inductor Connection

Low-Noise Mode Control. Forces fixed-frequency PWM operation when high.

______Standard Application Circuit

The basic MAX1636 buck converter (Figure 1) is easily

adapted to meet a wide range of applications with

inputs up to 30V by substituting components from

Table 1. These circuits represent a good set of trade-

offs between cost, size, and efficiency, while staying

within the worst-case specification limits for stress-

related parameters, such as capacitor ripple current.

Do not change the circuits’ switching frequency without

first recalculating component values (particularly induc-

tance value at maximum battery voltage). Adding a

Schottky rectifier across the synchronous rectifier

improves circuit efficiency by approximately 1%. This

rectifier is otherwise not needed because the MOSFET

required typically incorporates a high-speed silicon

diode from drain to source. Use a Schottky rectifier

rated at a DC current equal to at least one-third of the

load current.

8 _______________________________________________________________________________________

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