EN

LDO1

0

1

2

3

4

5

6

7

LDO2

tBON

tS

Timing Code

Timing Code

START UP sequence

SHUT DOWN sequence

is in reverse order of START UP sequence

EN

LDO1

0

1

2

3

4

5

6

7

LDO2

LDO3

LDO3

LDO4

LDO4

LDO5

LDO5

BUCK

BUCK

STANDBY

START UP

tS

tS

tS

tS

tS

tS

tS

tS

tS

tS

tS

tS

tS

SHUT DOWN

STANDBY

IDLE

Note 3

Note 3

Note 4

Note 5

LP8720

SNVS575B – JULY 2008 – REVISED MAY 2013

www.ti.com

DVS: Dynamic Voltage Scaling allows using 2 voltage sets for BUCK. There are 2 possibilities to use DVS:

1) Control via Serial Interface.

2) Control by DVS pin.

INTERRUPT: If interrupt is not masked, the PMU forces IRQ_N low if the temperature crosses the TSD_EW limit

(thermal shutdown early warning) or/and a thermal shutdown event has taken place. IRQ_N is released by

reading Interrupt register.

Power-On and Power-Off Sequences

tBON 150 µs – Reference and bias turn ON. Min 100 µs max 200 µs.

tS 25 µs – time step. Time step accuracy is defined by OSC frequency accuracy.

(1)

STARTUP and SHUTDOWN sequences are defined by registers. Sequences given here are valid if there the

registers are not rewritten via Serial Interface.

(2)

The timing showed here define time points when LDO’s and BUCK are enabled/disabled. Enabling /disabling process

duration depends on loading conditions. Buck startup duration is 140 µs for no load. LDO startup duration is no more

than 35 µs. For details please see LDO’s and BUCK Electrical Specifications.

(3)

LDO5 and BUCK are disabled. If LDO5 and/or BUCK are enabled via Serial Interface, and startup sequence is not

changed via Serial interface, then LDO5 and BUCK are disabled with no delay from falling edge on EN pin.

(4)

At this time point registers 0x09 and 0x0C are reset to POR default values.

(5)

At this time point registers 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 and 0x08 are reset to POR default values.

Figure 2. Startup Sequence if DEFSEL=VBATT or DEFSEL=Hi-Z

4

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