SP2026 Datasheet, PDF (4/14 Pages) Sipex Corporation – +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 100mΩ and
a supply current of 100µA. 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.
4) 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 V_IN 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 100mΩ 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 is
IN
greater than +2.4V.
After the switch turns on, if the voltage at V_IN
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.
Rev. 1/23/02
SP2026 +2.7V to +5.5V USB Power Control Switch
4
© Copyright 2002 Sipex Corporation