10
SC33001A/SC33001AH
3A Load Switch
The SC33001A/AH are a family of an ultra-low Rdson load
switch optimized for use in battery powered applications.
This family of device supports up to 3A continuous output
current. Sophisticated integrated circuitry maximizes
Vgs of the power NMOS to minimize Rdson resistance
over a wide range of operating conditions.
Input Capacitor
The primary purpose of input capacitance for SC33001A/
AH is to hold the voltage at VIN pins constant when the
switch is transition between open and closed. When the
switch is closing, the input capacitor prevents the voltage
at VIN from dropping. When the switch is opening, the
input capacitor limits voltage spikes.
Ceramic capacitors should be derated for temperature and
bias. As a result, applications up to 3.6V should use capaci-
tors rated 6.3V. Applications up to 5.5V should use capaci-
tors rated 10V.
Output Capacitor
The purpose of output capacitance is to absorb transients
on the output. Cin should be selected to be higher in
value than Cout. This is because the integrated body
diode of the SC33001A/AH does not have reverse voltage
protection. If the input supply is removed while the
switch is closed, Cin higher than Cout helps prevent
reverse bias of the integrated body diode.
Use the same voltage rating criteria for the output capaci-
tor as the input capacitor as described in above section.
Output Voltage Pull-down
The SC33001A has an internal pull-down resistor. When
the SC33001A is disabled, the output pull-down resistor
discharges the output capacitor through 1.1 kΩ.
Protection
The SC33001A/AH have current limit protection (OCP).
Current limit is quickly invoked when Vin current exceeds
current limit threshold (ILIM). The current limit is then
folded back to current limit foldback (ILIM_FOLD). This fold
back limit will be held for about 100µs before it can be
released back to it’s full value current limit (ILIM). The deci-
sion to raise current limit back to it’s full value is based on
the voltage at Vout. If the voltage on Vout is approxi-
mately 90% of VIN ( VRth_ILIM_TR) and the part has been in
foldback for the minimum time, then current limit is
returned to it’s full value (ILIM).
Startup into a short circuit behavior is illustrated in Figure
1. As the switch current increases beyond the over-cur-
rent protection threshold, the device will go into foldback
current limit. The current is regulated to the reduced fold-
back current limit level. Upon the short circuit removal,
as the load current is smaller than the foldback current
limit, the output voltage will rise. When the output volt-
age rises to ~90% of VIN, current limit will return to the
normal over-current protection level and resume normal
operation.
Figure 1 — Startng into Short Circuit and Recovery
from Short Circuit Removal Behavior
SC33001A/AH have over-temperature protection (OTP).
If the junction temperature rises to a typical value of 160
degree (Tth), the device will shutdown. Once the tempera-
ture drops by about 38 degree (Thys), the device will re-
start automatically. In case the output is shorted and OTP
has been triggered, the restart or hiccup mode operation
current limit will be held at fold back current limit (ILIM_FOLD),
refer to the waveform in page 7.
With a permanent short circuit on the output, the device
junction temperature will be “regulated” by the OTP cir-
cuits. The temperature will cycel between Tth and (Tth-Thys)
with alternate operation of current limit at ILIM_FOLD and
shutdown modes.
Applications Information
