SP2026 datasheet(4/14 Pages) SIPEX

4 / 14 page

Rev. 1/23/02

SP2026 +2.7V to +5.5V USB Power Control Switch

FEATURES

Features of the SP2026 device include current

limiting, a +2.4V undervoltage lockout,

overtemperature shutdown, error flag output,

soft start, a switch-on resistance of 100m

Ω and

a supply current of 100

µA. The SP2026-1 de-

vice has an active-high enable. The SP2026-2

device has an active-low enable.

THEORY OF OPERATION

The SP2026 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 SP2026 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 +2.4V.

Current Limiting Threshold:

A current

limiting threshold prevents damage to the de-

vice and external load.

5) Thermal Shutdown: The SP2026 has dual

sensors to detect overtemperature. If the die

temperature reaches 140

°C and channel A is in

current limit, output switch A is disabled and

flag A is asserted. Unless channel B current

limits, switch B remains enabled and flag B is

not asserted. If the die temperature reaches

140

°C and channel B is in current limit, output

switch B is disabled and flag B is asserted.

Unless channel A current limits, switch A re-

mains enabled and flag A is not asserted. If the

die exceeds 160

°C, both output switches are

disabled and both flags are asserted. A device is

disabled in thermal shutdown until the excessive

current load is removed, the appropriate enable pins

are toggled, or the temperature cools to 120

°C.

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 resistance when

closed. The output MOSFETs and driver cir-

cuitry 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. Overcurrent

2. Overtemperature

Undervoltage Lockout

This voltage lockout mechanism prevents the

MOSFET switches from turning on until V

IN is

greater than +2.4V.

After the switch turns on, if the voltage at V

drops below +2.15V, the lockout circuitry shuts

off both switches. This detection functions only

when at least one MOSFET switch is enabled.

Output Current Limiting

The SP2026 has a preset current-limit threshold.

These switch control circuits will implement cur-

rent limiting which prevents damage to the SP2026

and the external load while allowing a minimum

current of 0.5A to be delivered to the load.

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