SP2526 datasheet(4/18 Pages) SIPEX

4 / 18 page

Rev. 8/21/01

SP2526 +3.0V to +5.5V USB Power Control Switch

FEATURES

Features of the SP2526 device include current

limiting, a +2.7V undervoltage lockout, over-

temperature shutdown, error flag output, soft

start, a switch-on resistance of 100m

Ω over the

entire supply range, and a supply current of

100

µA. The SP2526-1 device has an active-

high enable.

The SP2526-2 device has an

active-low enable.

THEORY OF OPERATION

The SP2526 is a dual integrated high-side power

switch optimized for self-powered and bus-

powered Universal Serial Bus (USB) applica-

tions. There are operational conditions that will

enable or disable one or more of the output

MOSFET switches, depending on the type of

hazard. Certain conditions will activate the

open-drain error flag transistors forcing the flag

outputs to ground. The SP2526 provides the

following functions:

1) Independent Solid State Switches: Indepen-

dent MOSFET switches connect the IN pin to

the OUTA and OUTB pins when enabled by

logic signals at the ENA and ENB control pins.

2) Fault Flag Conditions: Both the FLGA and

FLGB pins are N-channel, open-drain MOSFET

outputs capable of sinking a 10mA load to

typically 100mV above ground.

3) Undervoltage Lockout: The lockout mecha-

nism monitors the input voltage and will enable

the MOSFET switches only when the voltage at

the V

IN pin is greater than +2.7V.

Current Limiting Threshold:

A current

limiting threshold prevents damage to the de-

vice and external load.

5) Thermal Shutdown: This mechanism pro-

tects the SP2526 and signals a fault condition if

the die temperature exceeds 135OC (typical).

This function has 10OC of hysteresis that pre-

vents the MOSFET switches from turning on

until the die temperature drops to 125OC (typi-

cal).

Input and Output

The independent solid state MOSFET switches

connect the USB +5.0V supply voltage at the IN

pin to the OUTA and OUTB pins when enabled

by logic signals at ENA and ENB. The IN pin is

the power supply connection to the device and the

drain of the output MOSFET switches.

Typically, the current will flow through the

switches from IN to OUTA and OUTB towards

the load. If V

OUT is greater than VIN when a switch

is enabled, the current will flow from OUTA or

OUTB to the IN pin because the MOSFET chan-

nels are bidirectional when switched on.

Under normal operating condition, the MOSFET

switches will present 100m

Ω maximum resis-

tance when closed. The output MOSFETs and

driver circuitry are designed to allow the MOSFET

source to be externally forced to a higher voltage

than the drain when the switch is off.

Fault Flag Conditions

Fault conditions disable one or both MOSFET

switches, depending on the type of fault. FLGA

and FLGB are N-channel, open-drain MOSFET

outputs. The active low fault flag occurs when

one of the following conditions exist:

1. Undervoltage

2. Overcurrent

3. Overtemperature

Undervoltage Lockout

This voltage lockout mechanism prevents the

MOSFET switches from turning on until V

IN is

greater than +2.7V.

After the switch turns on, if the voltage at V

drops below +2.6V, the lockout circuitry shuts off

both switches and signals the FLGA and FLGB

fault flags. In the undervoltage lockout state, the

FLGA and FLGB pins will be asserted. This

detection functions only when at least one

MOSFET switch is enabled.

Output Current Limiting

The SP2526 has a preset current-limit threshold.

These switch control circuits will implement

current limiting which prevents damage to the

SP2526 and the external load while allowing a

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