Rainbow-electronics MAX1563 User Manual download pdf (Page 7)

Detailed Description

The MAX1562/MAX1562H/MAX1563 family comprises a

programmable current-limited switch designed for USB

and hot-swap applications. The MAX1563 can be pro-

grammed for loads up to 4A, and the MAX1562/

MAX1562H can be programmed for loads up to 3A. The

current limit is programmed using a single resistor. A fault

output notifies the host when the current-limit, short-cir-

cuit, UVLO, or thermal-shutdown threshold is exceeded.

A built-in current limit protects the load and the source

in the event of an overload condition. In addition, a

built-in short-circuit detection circuit pulses the output if

the output is less than 1V (typ), resulting in a lower RMS

output current and reduced power dissipation in the

device. Thermal shutdown protects the device in the

event of a prolonged overload or short-circuit condition.

An internal micropower charge pump generates the

high-side supply needed for driving the gate of the

internal low-R

NMOS switch.

Fault blanking allows the MAX1562/MAX1562H/

MAX1563 family to handle USB loads that may not be

fully compliant with USB specifications. USB loads with

additional bypass capacitance or large startup currents

can be successfully powered while protecting the

upstream power source. If the switch brings up the

load within the blanking period (20ms typ), FAULT is

not asserted. In the event of a current-limit event, cur-

rent through the switch is regulated at the current-limit

target. Below approximately 1V, the short-circuit current

limit is 30% higher than the programmed current limit.

Current-Limit Programming

The MAX1562/MAX1562H/MAX1563 continuous current

limit is set by selecting the value of R

ISET

based on the

following equation:

LIM

= 17120 / R

ISET

Choose R

ISET

with resistor values between 4.22kΩ to

16kΩ. Resistor values greater than 16kΩ significantly

degrade current-limit accuracy. For the MAX1562/

MAX1562H, the minimum R

ISET

value is 5.76kΩ. This

corresponds to a 3A current limit, which is limited by

the 8-pin SO’s maximum power dissipation.

MAX1562/MAX1562H/MAX1563

Programmable 4A USB Current-Limited

Switches with Autoreset and Fault Blanking

_______________________________________________________________________________________ 7

Pin Description

MAX1562

MAX1562H

MAX1563

NAME FUNCTION

1 4 ON (ON)

Switch On/Off Control Input. The active polarity of ON is low for the MAX1562 and high

for the MAX1562H. For the MAX1563, the active polarity of ON is set by SEL.

25FAULT

Fault Indicator Output. FAULT is an open-drain output that asserts low when the switch

enters a sustained (>20ms) current limit. FAULT goes low immediately during thermal

shutdown or an undervoltage input. Note that during severe short conditions, FAULT

goes low immediately since there is typically also a brief undervoltage transient.

3 6 GND Ground

4 7 ISET

Current-Limit Input. Connect an external resistor from ISET to GND to set current limit,

where I

LIM

= 17120 / R

ISET

5, 7 9, 12 IN

Power Input for Switch. Connect both IN inputs together and bypass with a 1µF

ceramic capacitor to GND. Load conditions might require additional bulk capacitance

to prevent fluctuation on the input source.

6, 8 1, 10 OUT

Power Output for Switch. Bypass OUT to GND with a 4.7µF ceramic capacitor. Load

conditions might require additional bulk capacitance. When disabled, OUT goes into

a high-impedance state.

— 2, 8, 11 N.C.

No Connection. Internally unconnected. Leave unconnected or use with other traces

to simplify PC board layout.

— 3 SEL

Polarity Control Input for ON. Drive SEL high for active-high enable. Drive SEL low for

active-low enable.

1 2 3 4 5 6 7 8 9 10 11 12

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Rainbow-electronics MAX1563 User Manual Page 7

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