TPS5130

SLVS426 − MAY 2002

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10

DEAD-TIME

The internally defined dead-time prevents shoot-through-current flowing through the main power MOSFETs during

switching transitions. Typical value of the dead-time is 100 ns.

STANDBY

The SBRC controller, the LDO controller, and the internal regulators can be switched into standby mode separately as

shown in Table 1. The standby mode current, when both controllers and regulators are off, can be as low as 1 nA.

Table 1. Standby Logic

INPUT

FUNCTION

STBY_VREF5

SS_STBYx

STBY_VREF3.3

STBY_LDO

V(REG5V_IN) > 4.5V

VREF5

VREF3.3

SBRCx

LDO

L

L

L

L

False

OFF

OFF

OFF

OFF

L(1)

L(1)

L(1)

L(1)

True(1)

ON(1)

OFF(1)

OFF(1)

OFF(1)

H

L

L

L

x

ON

OFF

OFF

OFF

L

H

L

L

x

OFF

OFF

OFF

OFF

H

H

L

L

x

ON

OFF

ON

OFF

L

L

H

L

x

ON

ON

OFF

OFF

H

L

H

L

x

ON

ON

OFF

OFF

L

H

H

L

x

ON

ON

OFF

OFF

H

H

H

L

x

ON

ON

ON

OFF

L

L

L

H

x

ON

OFF

OFF

ON

H

L

L

H

x

ON

OFF

OFF

ON

L

H

L

H

x

ON

OFF

OFF

ON

H

H

L

H

x

ON

OFF

ON

ON

L

L

H

H

x

ON

ON

OFF

ON

H

L

H

H

x

ON

ON

OFF

ON

L

H

H

H

x

ON

ON

OFF

ON

H

H

H

H

x

ON

ON

ON

ON

(1) This functional mode is not recommended.

x = true or false

SOFT START

Soft start ramp up of the SBRC is controlled by the SS_STBYx pin voltage, which is controlled by an internal current source

and an external capacitor connected between the SS_STBYx and GND pins. When the STBY_VREF5 and/or SS_STBYx

pin voltages are forced to LOW, the SBRCx is disabled. When the STBY_VREF5 pin voltage is set to HIGH and the

SS_STBYx pin floats, the internal current source starts to charge the external capacitor. The output voltage ramps up as

the SS_STBYx pin voltage increases from 0 V to 0.85 V. The soft start time is easily calculated from the supply current and

the capacitance value (see application information). The soft start timing circuit for the LDO is integrated into the device.

The soft start time is fixed and can be as short as 600

µs. This is observed when the LDO is turned on separately from the

SBRC. Simultaneous start-up of one of the SBRC and the LDO, is also possible. Tie the LDO input to the SBRCx’s output,

let both the STBY_VREF5 and STBY_LDO voltages rise to the HIGH level, and invoke Soft start on the SS_STBYx pin;

then the LDO’s output follows the ramp of the SBRCx’s output.