(

)

(

)

(

)

-

´

=

+

=

+

´

´ ´

´

´

IND(ripple)

IN

OUT

OUT

TRIP

TRIP

OCP

SW

IN

DS(on)

DS(on)L

I

V

V

V

V

V

1

I

2

2 L f

V

8 R

8 R

=

´

TRIP

TRIP

TRIP

V

R

I

TPS53513

www.ti.com

SLUSBP9A – SEPTEMBER 2013 – REVISED DECEMBER 2013

Power-Good

The TPS53513 has power-good output that indicates high when switcher output is within the target. The power-

good function is activated after the soft-start operation is complete. If the output voltage becomes within ±8% of

the target value, internal comparators detect the power-good state and the power-good signal becomes high

after a 1-ms internal delay. If the output voltage goes outside of ±16% of the target value, the power-good signal

becomes low after a 2-

μs internal delay. The power-good output is an open-drain output and must be pulled-up

externally.

Current Sense and Overcurrent Protection

The TPS53513 has cycle-by-cycle overcurrent limiting control. The inductor current is monitored during the OFF

state and the controller maintains the OFF state during the period that the inductor current is larger than the

overcurrent trip level. In order to provide good accuracy and a cost-effective solution, the TPS53513 supports

where

•

•

•

(5)

The inductor current is monitored by the voltage between the GND pin and SW pin so that the SW pin is properly

Connect the GND pin to the proper current sensing device, (for example, the source terminal of the low-side

MOSFET.)

where

•

•

(6)

used); in order to design for worst case minimum OCP, maximum low-side on-resistance value of 8 m

Ω should

be used.

During an overcurrent condition, the current to the load exceeds the current to the output capacitor thus the

output voltage tends to decrease. Eventually, the output voltage crosses the undervoltage-protection threshold

and shuts down.

For the TPS53513, the overcurrent protection maximum is recommended up to 12 A only.

Overvoltage and Undervoltage Protection

The TPS53513 monitors a resistor-divided feedback voltage to detect overvoltage and undervoltage. When the

feedback voltage becomes lower than 68% of the target voltage, the UVP comparator output goes high and an

internal UVP delay counter begins counting. After 1 ms, the TPS53513 latches OFF both high-side and low-side

MOSFETs drivers. The UVP function enables after soft-start is complete.

When the feedback voltage becomes higher than 120% of the target voltage, the OVP comparator output goes

high and the circuit latches OFF the high-side MOSFET driver and turns on the low-side MOSFET until reaching

a negative current limit. Upon reaching the negative current limit, the low-side FET is turned off and the high-side

FET is turned on again for a minimum on-time. The TPS53513 operates in this cycle until the output voltage is

pulled down under the UVP threshold voltage for 1 ms. After the 1-ms UVP delay time, the high-side FET is

latched off and low-side FET is latched on. The fault is cleared with a reset of VDD or by re-toggling EN pin.

Copyright © 2013, Texas Instruments Incorporated

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