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UDG-11193

Switching Modulator

Output

Capacitor

TPS53353

VIN

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TPS53353

www.ti.com

SLUSAK2B – AUGUST 2011 – REVISED FEBRUARY 2015

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 latches ON the low-side MOSFET driver. The

output voltage decreases. If the output voltage reaches UV threshold, then both high-side MOSFET and low-side

MOSFET driver will be OFF and the device restarts after a hiccup delay. If the OV condition remains, both high-

side MOSFET and low-side MOSFET driver remains OFF until the OV condition is removed.

7.3.8 UVLO Protection

The TPS53353 uses VREG undervoltage lockout protection (UVLO). When the VREG voltage is lower than 3.95

V, the device shuts off. When the VREG voltage is higher than 4.2V, the device restarts. This is a non-latch

protection.

7.3.9 Thermal Shutdown

TPS53353 monitors the temperature of itself. If the temperature exceeds the threshold value (typically 145°C),

TPS53353 is shut off. When the temperature falls about 10°C below the threshold value, the device will turn back

on. This is a non-latch protection.

7.4 Device Functional Modes

7.4.1 Small Signal Model

From small-signal loop analysis, a buck converter using D-CAP™ mode can be simplified as shown in Figure 37.

Figure 37. Simplified Modulator Model

The output voltage is compared with the internal reference voltage (ramp signal is ignored here for simplicity).

The PWM comparator determines the timing to turn on the high-side MOSFET. The gain and speed of the

comparator can be assumed high enough to keep the voltage at the beginning of each on cycle substantially

constant.

(5)

frequency.

(6)

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