SC5826 View Datasheet(PDF) - Semtech Corporation
Part Name
Description
MFG CO.
'SC5826' PDF : 8 Pages View PDF
HotSwitch™
USB Power Distribution Switch
SC5826
PRELIMINARY - February 18, 2000
DETAILED DESCRIPTION
The SC5826 HotSwitch™ is a dual port, high-side
switch optimized for power control & distribution in Uni-
versal Serial Bus (USB) applications. It features an n-
channel power MOSFET with a low on-state resistance
for meeting USB voltage regulation requirements. It
available with active high (SC5826-1) or active low
(SC5826-2) inputs.
In/Out
The input is the supply voltage connection to the drain
of the power switch MOSFET. The output is con-
nected to the source of the MOSFET. Under normal
operating conditions when the power switch is enabled,
current flows from the input to the output towards the
load. The power switch is designed to sustain a mini-
mum load current of 500mA in accordance with USB
specifications.
Charge Pump
An internal charge pump powers the MOSFET gate
drive circuit and provides the necessary voltage to pull
the gate above the source.
Control Logic
The gate drive circuit controls the gate voltage of the
MOSFET power switch. The gate drive circuit also
controls the rise & fall times of the power switch output
voltage. The typical “soft start” or output voltage rise
time is 1ms.
Enable Input
A logic signal at the enable (EN) pin activates the
power MOSFET switch. A logic 1 (SC5826-1) or logic
0 (SC5826-2) will bias the charge pump, gate drive,
and control circuitry turning on the power switch. A
logic signal of opposite polarity turns off the switch. If
both outputs are off, the device powers down. The en-
able input is compatible with 3V & 5V logic levels.
Error Flag
The error flag (FLG) output is an n-channel, open drain
MOSFET. The FLG pin is an active low during short
circuit, undervoltage, or thermal shutdown conditions.
The output remains low until the fault condition is re-
moved.
Thermal Sense
An internal thermal shutdown circuit turns off the power
switch output MOSFET when the die junction tempera-
ture exceeds 160°C. The output FLG pin is asserted
to a logic low signaling a fault condition. A built in hys-
teresis prevents the switch from turning on until the die
temperature has cooled approximately 10°C. The
switch will continue to cycle on and off until the fault
condition is removed. The thermal sense circuit func-
tions only when the switch is enabled.
Undervoltage Lockout
An undervoltage lockout circuit monitors the input volt-
age and prevents the power switch MOSFET from
turning on until the input voltage (IN) exceeds 2.5V
(typical). If the input voltage falls 90mV (typical) below
that point after the switch has been turned on, the un-
dervoltage lockout turns off the power switch output
MOSFET and asserts the FLG output to logic low. The
undervoltage lockout functions only when the switch is
enabled.
© 2000 SEMTECH CORP.
5
652 MITCHELL ROAD NEWBURY PARK CA 91320
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