Datasheet

TPS65023, TPS65023B

SLVS670J –JUNE 2006– REVISED SEPTEMBER 2011

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APPLICATION INFORMATION

Layout Considerations

As for all switching power supplies, the layout is an important step in the design. Proper function of the device

demands careful attention to PCB layout. Care must be taken in board layout to get the specified performance. If

the layout is not carefully done, the regulators may show poor line and/or load regulation, and stability issues as

well as EMI problems. It is critical to provide a low impedance ground path. Therefore, use wide and short traces

for the main current paths. The input capacitors should be placed as close as possible to the IC pins as well as

the inductor and output capacitor.

For TPS65023, TPS65023B, connect the PGND pins of the device to the PowerPAD™ land of the PCB and

connect the analog ground connections (AGND) to the PGND at the PowerPAD™. It is essential to provide a

good thermal and electrical connection of all GND pins using multiple vias to the GND-plane. Keep the common

path to the AGND pins, which returns the small signal components, and the high current of the output capacitors

as short as possible to avoid ground noise. The VDCDCx line should be connected right to the output capacitor

and routed away from noisy components and traces (for example, the L1, L2 and L3 traces).

Input Voltage Connection

The low power section of the control circuit for the step-down converters DCDC1, DCDC2 and DCDC3 is

supplied by the Vcc pin while the circuitry with high power such as the power stage is powered from the

VINDCDC1, VINDCDC2 and VINDCDC3 pins. For proper operation of the step-down converters, VINDCDC1,

VINDCDC2,VNDCDC3 and Vcc need to be tied to the same voltage rail. Step-down converters that are plannned

to be not used, still need to be powered from their input pin on the same rails than the other step-down

converters and Vcc.

LDO1 and LDO2 share a supply voltage pin which can be powered from the Vcc rails or from a voltage lower

than Vcc e.g. the output of one of the step-down converters as long as it is operated within the input voltage

range of the LDOs. If both LDOs are not used, the VINLDO pin can be tied to GND.

Requirements for Supply Voltages below 3.0V

For a supply voltage on pins Vcc, VINDCDC1, VINDCDC2 and VINDCDC3 below 3.0V, it is recommended to

enable the DCDC1, DCDC2 and DCDC3 converters in sequence. If all 3 step-down converters are enabled at

the same time while the supply voltage is close to the internal reset detection threshold, a reset may be

generated during power-up. Therefore it is recommended to enable the dcdc convertes in sequence. This can be

done by driving one or two of the enable pins with a RC delay or by driving the enable pin by the output voltage

of one of the other step-down converters. If a voltage above 3.0V is applied on pin VBACKUP while Vcc and

VINDCDCx is below 3.0V, there is no restriction in the power-up sequencing as VBACKUP will be used to power

the internal circuitry.

Unused Regulators

In case a step-down converter is not used, its input supply voltage pin VINDCDCx still needs to be connected to

the Vcc rail along with supply input of the other step-down converters. It is recommended to close the control

loop such that an inductor and output capacitor is added in the same way as it would be when operated

normally. If one of the LDOs is not used, its output capacitor should be added as well. If both LDOs are not used,

the input supply pin as well as the output pins of the LDOs (VINLDO, VLDO1, VLDO2) should be tied to GND.

Product Folder Link(s) :TPS65023 TPS65023B