TPS62933O datasheet(12/47 Pages) TI

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8 Detailed Description

8.1 Overview

The TPS62933 is a 30-V, 3-A, synchronous buck (step-down) converter with two integrated n-channel

MOSFETs. It employs fixed-frequency peak current control mode for fast transient response and good line and

load regulation. With the optimized internal loop compensation, the device eliminates the external compensation

components over a wide range of output voltage and switching frequency.

The integrated 76-mΩ and 32-mΩ MOSFETs allow for high-efficiency power supply designs with continuous

output currents up to 3 A. The feedback reference voltage is designed at 0.8 V. The output voltage can be

stepped down from 0.8 V to 22 V. It is ideally suited for systems powered from 5-V, 12-V, 19-V, and 24-V

power-bus rails.

The TPS62933 has been designed for safe monotonic start-up into pre-biased loads. The default start-up is at

VIN equal to 3.8 V. After the device is enabled, the output rises smoothly from 0 V to its regulated voltage. The

total operating current is 12 μA (typical) when not switching under no load. When the device is disabled, the

supply current is approximately 2 µA (typical). The pulse frequency modulation (PFM) mode maximizes the light

load efficiency. These features are extremely beneficial for long battery life time in low-power operation.

The EN pin has an internal pullup current that can be used to adjust the input voltage undervoltage lockout

(UVLO) with two external resistors. In addition, the EN pin can be floating for the device to operate with the

internal pullup current.

The switching frequency can be set by the configuration of the RT pin in the range of 200 kHz to 2.2 MHz, which

allows for efficiency and solution size optimization when selecting the output filter components. This device also

has frequency spread spectrum feature which helps with lowering down EMI noise.

The SS (soft start/tracking) pin is used to minimize inrush current when driving capacitative load. A small value

capacitor or resistor divider is connected to the SS pin for soft-start time setting or voltage tracking.

The device has the on-time extension function with a maximum on time of 7 μs (typical). During the low dropout

operation, the high-side MOSFET can turn on up to 7 μs, then the high-side MOSFET turns off and the low-side

MOSFET turns on with a minimum off time of 140 ns (typical). It supports the maximum 98% duty cycle.

The device reduces the external component count by integrating the bootstrap circuit. The bias voltage for the

integrated high-side MOSFET is supplied by a capacitor between the BST and SW pins. A UVLO circuit monitors

the bootstrap capacitor voltage VBST-SW. When it falls below a preset threshold of 2.5 V (typical), the SW pin is

pulled low to recharge the bootstrap capacitor.

Cycle-by-cycle current limiting on the high-side MOSFET protects the device in overload situations and is

enhanced by a low-side sourcing current limit, which prevents current runaway. The TPS62933 provides output

undervoltage protection (UVP) when the regulated output voltage is lower than 65% of the nominal voltage

due to overcurrent being triggered, about 256-μs (typical) deglitch time later, both the high-side and low-side

MOSFET turn off, the device steps into hiccup mode.

The device minimizes excessive output overvoltage transient by taking advantage of the overvoltage

comparator. When the regulated output voltage is greater than 115% of the nominal voltage, the overvoltage

comparator is activated, and the high-side MOSFET is turned off and masked from turning on until the output

voltage is lower than 110%.

Thermal shutdown disables the device when the die temperature, TJ, exceeds 165°C and enables the device

again after TJ decreases below the hysteresis amount of 30°C.

TPS62933

SLUSEA4A – JUNE 2021 – REVISED DECEMBER 2021

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