Datasheet

IN
OC1
EN1
OC2
2
8
5
7
0.1 µF 22 µF
0.1 µF 22 µF
Load
Load
OUT1
OUT2
Power Supply
2.7 V to 5.5 V
6
EN2
3
4
GND
0.1 µF
TPS2042B
1
TPS2041B, TPS2042B
TPS2043B, TPS2044B, TPS2051B
TPS2052B, TPS2053B, TPS2054B
SLVS514L –JUNE 2010–REVISED JUNE 2011 www.ti.com
APPLICATION INFORMATION
POWER-SUPPLY CONSIDERATIONS
Figure 31. Typical Application (Example, TPS2042B)
A 0.01-μF to 0.1-μF ceramic bypass capacitor between IN and GND, close to the device, is recommended.
Placing a high-value electrolytic capacitor on the output pin(s) 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-μF to 0.1-μF ceramic capacitor improves the immunity of the device to short-circuit transients.
OVERCURRENT
A sense FET is employed to check 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 17 through Figure 20). The TPS204xB/TPS205xB
senses the short and immediately switches into a constant-current output.
In the second condition, a short or an overload occurs while the device is enabled. At the instant the overload
occurs, high currents may flow for a short period of time before the current-limit circuit can react. After the
current-limit circuit has tripped (reached the overcurrent trip threshold), 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 Figure 21 through Figure 24). The TPS204xB/TPS205xB 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.
OC RESPONSE
The OCx open-drain output is asserted (active low) when an overcurrent or overtemperature shutdown condition
is encountered after a 10-ms deglitch timeout. The output remains asserted until the overcurrent or
overtemperature condition is removed. Connecting a heavy capacitive load to an enabled device can cause a
momentary overcurrent condition; however, no false reporting on OCx occurs due to the 10-ms deglitch circuit.
The TPS204xB/TPS205xB is designed to eliminate false overcurrent reporting. The internal overcurrent deglitch
eliminates the need for external components to remove unwanted pulses. OCx is not deglitched when the switch
is turned off due to an overtemperature shutdown.
18 Copyright © 2010–2011, Texas Instruments Incorporated