PIFE32251B-R68MS datasheet(68/157 Pages) TI1

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TPS650830

SLVSCF4A – DECEMBER 2014 – REVISED JULY 2016

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Detailed Description

6.3.13.5 Output Discharge Feature

All the voltage regulators have a built in output discharge feature. The output discharge feature consists of

being able to configure register bits to enable a discharge resistor which is only active whenever the

voltage regulator is disabled. The discharge resistors for each of the voltage regulators can be configured

using the DISCHCNT1, DISCHCNT2, DISCHCNT3 and DISCHCNT4 registers. The discharge resistors

are disconnected when the voltage regulators are enabled in order to minimize any losses within the

PMIC.

6.3.13.6 Output Voltage Control

All voltage regulators are designed to regulate a fixed output voltage. To achieve high accuracy the output

voltage for the converters and controller is sensed using a separate feedback pin. For each of the voltage

rails, except for the VTT LDO, the output voltage can be changed to slightly higher or lower values by

changing the default setting in the voltage regulator control registers (see section on the Voltage

Regulator Voltage Options). This function can be used to save power when supplying the connected load

at its minimum possible supply voltage or to compensate for voltage drops during load transients by

programming it slightly higher. In addition the range of the output voltage for the regulators is highly

programmable. If you need a different output voltage configuration from the specified default, please

contact TI to generate you a custom part.

6.3.13.7 Converter Low Power Mode Operation

For optimizing low power operation, the output voltage of the converters can be set to a specific value.

The low power output voltage is set by the specific register and bits shown in the Voltage Regulator

Voltage Options tables. Entering the low power mode is accomplished by asserting the SLP_S0# signal to

a logic low. In this low power mode, the powergood function remains active and is not affected by the

transition from normal operation mode to the low power mode and vice versa.

6.3.13.8 Controller Low Power Mode Operation

For optimizing low power operation, the output voltage of the controllers can be set to a specific value.

The low power output voltage is set by the specific register and bits shown in the Voltage Regulator

Voltage Options tables. Entering the low power mode is accomplished by asserting the DDR_VTT_CTRL

pin or the STANDBYZ pin to a logic low. In this low power mode, the powergood function remains active

and is not affected by the transition from normal operation mode to the low power mode and vice versa.

DDR_VTT_CTRL pin asserts DVS on VR4, while STANDBYZ pin asserts DVS in VR1, VR2, VR3, and

VR5, as defined by ther CNT registers. In situations where the output current demand from the controller

is very small, the controller is automatically placed in an Ultra Low Quiescent (ULQ) mode to reduce

power consumption and increase the efficiency.

6.3.13.9 Controller Internal Ramp Comparator

The controllers have an internal ramp, characteristic of th DCAP2 control architecture, to give improved

performance with low-ESR output capacitors. This internal ramp provides ramp compensation that helps

maintain a relatively constant frequency during CCM, and it provides better stability for designs with very

low ESR on the output capacitors. The ramp height can be optimized and is a function of the input voltage

to provide proportional feed-forward. At very high voltages, the ramp may exceed the operating window of

the PWM comparator and may overpower the natural ripple of the output, so there is a need to switch to a

smaller ramp. As the ramp was already getting large, it helps to switch back to a smaller size. To achieve

this, a comparator monitors the input voltage at the VIN pin. When input voltage rises and exceeds 11 V, it

changes the ramp to a slightly smaller value. There is a wide 1.1-V hysteresis, so at approximately 9.9 V

as the Vin falls, the ramp returns to the slightly bigger size. In most cases this difference is negligible.

PIFE32251B-R68MS 데이터시트(PDF) 68 Page - Texas Instruments

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