Datasheet

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APPLICATION INFORMATION
IN
OC
EN
GND
0.1 µF
2,3
5
4
6,7,8
0.1 µF 22 µF
Load
1
OUT
TPS2024
Power Supply
2.7 V to 5.5 V
10 kΩ
POWER SUPPLY CONSIDERATIONS
OVERCURRENT
OC RESPONSE
TPS2020 , , TPS2021
TPS2022 , TPS2023 , TPS2024
SLVS175C – DECEMBER 1998 – REVISED SEPTEMBER 2007
Figure 38. Typical Application
A 0.01- μ F to 0.1- μ F ceramic bypass capacitor between IN and GND, close to the device, is recommended.
Placing a high-value electrolytic capacitor on the output and input pins is recommended when the output load is
heavy. This precaution reduces power supply transients that may cause ringing on the input. Additionally,
bypassing the output with a 0.01- μ F to 0.1- μ F ceramic capacitor improves the immunity of the device to
short-circuit transients.
A sense FET checks for overcurrent conditions. Unlike current-sense resistors, sense FETs do not increase the
series resistance of the current path. When an overcurrent condition is detected, the device maintains a constant
output current and reduces the output voltage accordingly. Complete shutdown occurs only if the fault is present
long enough to activate thermal limiting.
Three possible overload conditions can occur. In the first condition, the output has been shorted before the
device is enabled or before V
I(IN)
has been applied, see Figure 6 . The TPS202x senses the short and
immediately switches into a constant-current output.
In the second condition, the excessive load occurs while the device is enabled. At the instant the excessive load
occurs, very high currents may flow for a short time before the current-limit circuit can react (see Figures 13 – 22).
After the current-limit circuit has tripped (reached the overcurrent trip threshhold) the device switches into
constant-current mode.
In the third condition, the load has been gradually increased beyond the recommended operating current. The
current is permitted to rise until the current-limit threshold is reached or until the thermal limit of the device is
exceeded (see Figures 7 – 11). The TPS202x is capable of delivering current up to the current-limit threshold
without damaging the device. Once the threshold has been reached, the device switches into its constant-current
mode.
The OC open-drain output is asserted (active low) when an overcurrent or overtemperature condition is
encountered. The output remains asserted until the overcurrent or overtemperature condition is removed.
Connecting a heavy capacitive load to an enabled device can cause momentary false overcurrent reporting from
the inrush current flowing through the device, charging the downstream capacitor. An RC filter can be connected
to the OC pin to reduce false overcurrent reporting. Using low-ESR electrolytic capacitors on the output lowers
the inrush current flow through the device during hot-plug events by providing a low impedance energy source,
thereby reducing erroneous overcurrent reporting.
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