TPS65279V_15 Datasheet, PDF (20/46 Pages) Texas Instruments – 4.5-V TO 18-V INPUT VOLTAGE, 5-A/5-A DUAL SYNCHRONOUS STEP-DOWN CONVERTER WITH I2C CONTROLLED VID AND CURRENT SHARING

TPS65279V
SLVSBW1B – FEBRUARY 2013 – REVISED JANUARY 2014
OVERVIEW
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TPS65279V is a dual 5-A/5-A output current, synchronous step-down (buck) converter with integrated
n-channel MOSFETs. A wide 4.5-V to 18-V input supply range to buck encompasses most intermediate bus
voltages operating off 9-V, 12-V or 15-V power bus.
TPS65279V is equipped with I²C compatible bus for sophisticated control and communication with SoC. With I²C
interface, SoC can enable or disable the power converters, set output voltage and read status registers. The
buck regulator has external feedback resistors that can be used for setting the initial start up voltage. The
feedback voltage reference for this start-up option is 0.6V. Once the voltage identification VID DAC is updated
via the I²C, output voltage of each channel can be independently programmed with 7 bits VID from 0.68 V to
1.95 V in 10-mV steps. Output voltage transitions begin once the I²C interface receives the command for GO bit
in command registers. In light loading condition, low pulse skipping mode can be I²C controlled or selected with
MODE pin configuration.
TPS65279V implements a constant frequency, peak current mode control which simplifies external frequency
compensation. The wide switching frequency of 200 kHz to 1600 kHz allows for efficiency and size optimization
when selecting the output filter components. The switching frequency can be adjusted with an external resistor to
ground on the ROSC pin. The TPS65279V also has an internal phase lock loop (PLL) controlled by the ROSC
pin that can be used to synchronize the switching cycle to the falling edge of an external system clock. 180° out-
of-phase operation between two channels reduces input filter and power supply induced noise.
TPS65279V has been designed for safe monotonic startup into pre-biased loads. The default start up is when
VIN is typically 4.5 V. The EN pin has an internal pull-up current source that can be used to adjust the input
voltage under voltage lockout (UVLO) with two external resistors. In addition, the EN pin can be floating for
automatically starting up the TPS65279V with the internal pull up current.
The integrated MOSFETs of each channel allow for high efficiency power supply designs with continuous output
currents up to 5 A. The MOSFETs have been sized to optimize efficiency for lower duty cycle applications.
The TPS65279V reduces the external component count by integrating the boot recharge circuit. The bias voltage
for the integrated high-side MOSFET is supplied by a capacitor between the BOOT and LX pins. The boot
capacitor voltage is monitored by a BOOT to LX UVLO (BOOT-LX UVLO) circuit allowing LX pin to be pulled low
to recharge the boot capacitor. The TPS65279V can operate at 100% duty cycle as long as the boot capacitor
voltage is higher than the preset BOOT-LX UVLO threshold which is typically 2.1 V.
The TPS65279V has a power good comparator (PWRGD) with hysteresis which monitors the output voltage
through internal feedback voltage. I²C can read the power good status with commanding register.
The SS (soft start/tracking) pin is used to minimize inrush currents or provide power supply sequencing during
power up. A small value capacitor or resistor divider should be coupled to the pin for soft start or critical power
supply sequencing requirements.
The TPS65279V is protected from output overvoltage, overload and thermal fault conditions. The TPS65279V
minimizes excessive output overvoltage transients by taking advantage of the power good comparator. When the
overvoltage comparator is activated, the high-side MOSFET is turned off and prevented from turning on until the
internal feedback voltage is lower than 108% of the 0.6-V reference voltage. The TPS65279V implements both
high-side MOSFET overload protection and bidirectional low-side MOSFET overload protections which help
control the inductor current and avoid current runaway. If the over current condition has lasted for more than the
hiccup wait time, the TPS65279V will shut down and re-start after the hiccup time. The TPS65279V also shuts
down if the junction temperature is higher than thermal shutdown trip point. When the junction temperature drops
20°C typically below the thermal shutdown trip point, the built-in thermal shutdown hiccup timer is triggered. The
TPS65279V will be restarted under control of the soft start circuit automatically after the thermal shutdown hiccup
time is over.
Furthermore, if the over-current condition has lasted for more than the hiccup wait time which is programmed for
512 switching cycles, the TPS65279V will shut down itself and re-start after the hiccup time which is set for
16384 cycles. The hiccup mode helps to reduce the device power dissipation under severe over-current
conditions.
The TPS65279V operates at any load conditions unless the COMP pin voltage drops below the COMP pin start
switching threshold which is typically 0.25 V.
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