TPS61080

TPS61081

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SLVS644D – FEBRUARY 2006 – REVISED APRIL 2013

IC attempts to start up one time. After 57ms, the IC restarts in a fashion described in the above section. If the

short is cleared, the boost regulator properly starts up and reaches output regulation. However, after reaching

regulation, if another event of short circuit current limit occurs, the IC goes into shutdown mode again, and the

fault can only be cleared by toggling the EN pin or POR. Under a permanent short circuit, the IC shuts down after

a start up failure and waits for POR or the EN pin toggling.

The same circuit also protects the ICs and external components when the SW pin is shorted to ground. These

features provide much more comprehensive and reliable protection than the conventional boost regulator.

Table 1 lists the IC protection against the short of each IC pin.

Table 1. TPS61080/1 Short Circuit Protection Mode

SHORTED TO GND

FAULT DETECTION

IC OPERATION

HOW TO CLEAR THE FAULT

IC restarts after 57ms; If it happens again,

L, SW

Turn off isolation FET

the fault can only be cleared by toggling

EN or POR.

OUT (during start

OUT <Vin– 1.4V for 2 ms

IC shuts down

Cleared by toggling EN or POR

up)

OUT (after start up)

OUT <Vin– 1.4V without delay

IC shuts down

Cleared by toggling EN or POR

EN

N/A

IC disabled

N/A

FSW

N/A

600 kHz switching frequency

N/A

Disable PWM switching and no output;

SS

N/A

N/A

but still dissipate quiescent current.

FB

N/A

Over voltage protection of the OUT pin OUT voltage fails by OVP hysteresis

GND, PGND, VIN

N/A

N/A

N/A

OVERVOLTAGE PROTECTION

When TPS61080/1 is configured as regulated current output as shown in the TYPICAL APPLICATIONS, the

output voltage can run away if the current load is disconnected. The over voltage condition can also occur if the

FB pin is shorted to the ground. To prevent the SW node and the output capacitor from exceeding the maximum

voltage rating, an over voltage protection circuit turns off the boost regulator as soon as the output voltage

exceeds the OVP threshold. When the output voltage falls 0.7V below the OVP threshold, the regulator resumes

the PWM switching unless the output voltage exceeds the OVP threshold.

UNDERVOLTAGE LOCKOUT (UVLO)

An undervoltage lockout prevents mis-operation of the device for input voltages below 1.65 V (typical). When the

input voltage is below the undervoltage threshold, the device remains off and both PWM and isolation switch are

turned off, providing isolation between input and output. The undervoltage lockout threshold is set below

minimum operating voltage of 2.5V to avoid any transient VIN dip to trigger UVLO and causes converter reset.

For the VIN voltage between UVLO threshold and 2.5V, the IC still maintains its operation. However, the spec is

not assured.

THERMAL SHUTDOWN

An internal thermal shutdown turns off the isolation and PWM switches when the typical junction temperature of

160°C is exceeded. The IC restarts if the junction temperature drops by 15°C.

ENABLE

Connecting the EN pin low turns off the power switch immediately, but keeps the isolation FET on. If the EN pin

is logic low for more than 74ms, the IC turns off the isolation FET and enters shutdown mode drawing less than

1

μA current. The enable input pin has an internal 800kΩ pull down resistor to disable the device when the pin is

floating.

Copyright © 2006–2013, Texas Instruments Incorporated

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