TPS544B20 Datasheet, PDF(21/75 Page) Texas Instruments – 4.5-V to 18-V, 20-A, and 30-A SWIFT Synchronous Buck Converters with PMBus

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TPS544B20 Datasheet, PDF (21/75 Pages) Texas Instruments – 4.5-V to 18-V, 20-A, and 30-A SWIFT Synchronous Buck Converters with PMBus

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TPS544B20, TPS544C20

SLUSB69B â MAY 2014 â REVISED JULY 2016

8.3.9 External Bypass (BPEXT)

The BPEXT pin provides an external bypass of the internal BP6 regulator when the application includes an

external bias supply between 4.5 V and 6.5 V. Using an external supply reduces the power dissipation in these

devices and can slightly improve system efficiency. If the input voltage is less than the UVLO threshold, or if the

voltage on the BPEXT pin is lower than the switch-over voltage, VBPEXT(swover), these devices use the internal BP6

regulator. If the voltage on the BPEXT pin exceeds this switch-over voltage, then these devices disable the

internal BP6 regulator and BPEXT outputs to BP6, replacing the internal linear regulator, until the voltage on the

BPEXT pin falls by the BPEXT switch-over hysteresis amount, VHYS(swover). If the application does not require the

BPEXT function, connect the BPEXT pin to GND.

12 V

VDD

Level Shift

Logic

VIN OK

BPEXT OK

VDD

BP6_INT

6.5 V

4.2 V

6.5 V

BP6

BPEXT

VBPEXT(swover)

BPEXT

BP6

6.5 V

4.7 V

4.5 V

4.5V

6.5 V

Figure 24. BP External

UDG-12251

Figure 25. BP Crossover Diagram

NOTE

It is not recommended to transition BPEXT across the switch-over voltage, VBPEXT(swover),

during regulation. The transition causes an overshoot or undershoot response on the

output voltage. Instead, the BPEXT voltage should be either fully established to its final

level, or pulled low to GND prior to entering regulation.

8.3.10 Current Monitoring and Low-Side MOSFET Overcurrent Protection

The TPS544C20 and TPS544B20 devices sense average output current using an internal sensefet. A sensefet

conducts a scaled-down version of the power-stage current. Sampling this current in the middle of the low-side

drive signal determines the average output current. This architecture achieves excellent current monitoring and

better overcurrent threshold accuracy than inductor DCR current sensing with minimal temperature variation and

no dependence on power loss in a higher DCR inductor. This enables the use of lower DCR inductors to improve

efficiency. Use the IOUT_CAL_OFFSET command to improve current sensing and overcurrent accuracy by

removing board layout-related systematic errors post assembly. The devices continually digitize the sensed

output current, and average it to reduce measurement noise. The devices then store the current value in the

read-only READ_IOUT register, enabling output current telemetry.

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