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TPS562219A, TPS563219A

www.ti.com

SLVSDT2 – NOVEMBER 2016

Product Folder Links: TPS562219A TPS563219A

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Copyright © 2016, Texas Instruments Incorporated

Feature Description (continued)

7.3.2 Soft Start and Pre-Biased Soft Start

The TPS562219A and TPS563219A have adjustable soft-start. When the EN pin becomes high, the SS charge

(1)

If the output capacitor is pre-biased at startup, the devices initiate switching and start ramping up only after the

converters ramp up smoothly into regulation point.

7.3.3 Power Good

The power good output, PG is an open drain output. The power good function becomes active after 1.7 times

soft-start time. When the output voltage becomes within –10% of the target value, internal comparators detect

power good state and the power good signal becomes high. If the feedback voltage goes under 15% of the target

value, the power good signal becomes low.

7.3.4 Current Protection

The output over-current limit (OCL) is implemented using a cycle-by-cycle valley detect control circuit. The switch

current is monitored during the OFF state by measuring the low-side FET drain to source voltage. This voltage is

proportional to the switch current. To improve accuracy, the voltage sensing is temperature compensated.

above the OCL level, the converter maintains low-side FET on and delays the creation of a new set pulse, even

the voltage feedback loop requires one, until the current level becomes OCL level or lower. In subsequent

switching cycles, the on-time is set to a fixed value and the current is monitored in the same manner. If the over

current condition exists consecutive switching cycles, the internal OCL threshold is set to a lower level, reducing

the available output current. When a switching cycle occurs where the switch current is not above the lower OCL

threshold, the counter is reset and the OCL threshold is returned to the higher value.

There are some important considerations for this type of over-current protection. The load current is higher than

the over-current threshold by one half of the peak-to-peak inductor ripple current. Also, when the current is being

limited, the output voltage tends to fall as the demanded load current may be higher than the current available

from the converter. This may cause the output voltage to fall. When the VFB voltage falls below the UVP

threshold voltage, the UVP comparator detects it. And then, the device will shut down after the UVP delay time

(typically 14 µs) and re-start after the hiccup time.

When the over current condition is removed, the output voltage returns to the regulated value.

7.3.5 Over Voltage Protection

TPS562219A and TPS563219A detect over voltage condition by monitoring the feedback voltage (VFB). When

the feedback voltage becomes higher than 125% of the target voltage, the OVP comparator output goes high

and the high-side MOSFET turns off. This function is non-latch operation.

7.3.6 UVLO Protection

Under voltage lock out protection (UVLO) monitors the internal regulator voltage. When the voltage is lower than

UVLO threshold voltage, the device is shut off. This protection is non-latching.

7.3.7 Thermal Shutdown

The device monitors the temperature of itself. If the temperature exceeds the threshold value (typically 155°C),

the device is shut off. This is a non-latch protection.