IMP2524-1BN View Datasheet(PDF) - A1 PROs co., Ltd.

Part Name

Description

Manufacturer

IMP2524-1BN

Quad USB High-Side Power Switch with Fault Detection

A1 PROs co., Ltd. 

IMP2526

Detailed Descriptions

The IMP2526 dual high-side N-channel MOSFET switch inter-

faces with a USB controller by means of a Switch-Enable input

and a Fault-Flag output. The Enable input, with either a logic “1”

for the IMP2526-1 or logic “0” for the IMP2526-2, turns the power

MOSFET ON. Any one of three fault conditions will activate the

open-drain Fault-Flag Output to alert the controller that the

power MOSFET has been turned OFF.

Input and Output

The IN (input) pin is the power supply connection to the logic

circuitry and the “High-Side” of the switch (the Drain of the

power MOSFET). The OUTA/B (output) pin is the “Low-Side” of

the switch (the Source of the power MOSFET). In a typical circuit,

current flows through the switch from IN to OUT toward the

load. The switch is referred to as a “High-Side” switch since it dri-

ves the positive (or high) side of the load. The output MOSFET

source can be forced to a higher voltage than the drain (VOUT >

VIN) when the output is OFF with little leakage current. If, how-

ever, VIN drops below 2.3V, reverse current may flow out the IN

pin regardless of the enable state. When the power switch is ON,

current can flow in either direction.

Fault Flag - FLG Pin

The Fault Flag pin, FLGA/B, connects to an N-channel, open-

drain MOSFET and goes LOW (“0”) for an occurrence of one or

more of three conditions: undervoltage, current limit, or thermal

shutdown. The FLG output MOSFET is capable of sinking a

10mA load to typically 100mV above ground. Both flags may be

wire-NORed to a common pull-up resistor.

Thermal Shutdown

Thermal shutdown is active when the output switch is enabled

(turned ON). Thermal shutdown shuts off the output MOSFET

and sets the Fault Flag if the on-chip temperature sensor exceeds

135°C. The switch is held OFF until the die temperature drops to

125°C or below. This 10°C of hysteresis will result in ON-OFF

short-circuit cycling if the short-circuit condition is not removed

or the bus-controller does turn off the switch with the Enable

input. Over temperature detection is active only if the chip is

enabled.

Undervoltage Lockout

The Undervoltage lockout (UVLO) prevents the output

MOSFET from being put into the ON state until the positive sup-

ply voltage, VIN, exceeds 2.5V. When the output switch is in the

ON state and the positive supply voltage drops below 2.3V, the

UVLO circuitry will assert the Fault Flag, FLG, and shut OFF the

output MOSFET. The FLG output will only assert an active LOW

state when the MOSFET switch is in the ON state. Undervoltage

detection is active only if the chip is enabled.

Current Limiting

Current limiting is achieved by sensing the voltage drop from

Drain-to-Source of the power MOSFET. When the internal thresh-

old is exceeded the power MOSFET is turned OFF.

Table 1 gives the states of the FLG and OUT pins when a fault

condition is detected.

Table 1. Fault Flag Conditions - Switch Enabled

Condition

Thermal Shutdown

Undervoltage Lockout (UVLO)

Current Limiting

Cause

TJ > 135°C

VIN < 2.3V

IO > 0.5A (step load)

IO > 0.63A (ramped load)

FLG pin “0” Until

TJ ≤ 125°C

VIN > 2.5V

Enable off or

Thermal Shutdown

Switch State (FLG = “0”)

Turns OFF

Turns OFF

Stays ON*

* The switch and Fault Flag behavior during current-limiting is more complex than shown by this table. The detailed discussion on each of these

fault conditions gives additional information.

4

408-432-9100/www.impweb.com

© 2000 IMP, Inc. 6

Share Link: