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APPLICATION INFORMATION

POWER-SUPPLY CONSIDERATIONS

OVERCURRENT

POWER DISSIPATION AND JUNCTION TEMPERATURE

P

D +

r

DS(on)

I2

(1)

T

J +

P

D

R

q

JA )

T

A

(2)

TPS2010A, TPS2011A

TPS2012A, TPS2013A

SLVS189C – DECEMBER 1998 – REVISED SEPTEMBER 2007

Figure 35. Typical Application

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 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-

μF to 0.1-μF 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

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

Figure 12–Figure 19). 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 Figures Figure 77–Figure 10). The TPS201xA 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 low on-resistance on the n-channel MOSFET allows small surface-mount packages, such as SOIC, to pass

large currents. The thermal resistance of these packages are high compared to those of power packages; it is

input voltage and operating temperature. As an initial estimate, use the highest operating ambient temperature of

Finally, calculate the junction temperature:

18

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