LTC3589 datasheet(33/50 Pages) LINER

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LTC3589/LTC3589-1/

LTC3589-2

3589fe

Figure 14. PGOOD Pin and PGSTAT Status Register Timing

VOUTx

PGOOD

IRQ

3589 F14

ENx

200μs

25μs

1sec

14ms

250μs

ENABLE

DISABLE

UNDERVOLTAGE

DISABLED IF

WAKE LOW

WAKE HIGH AFTER 1sec

IF PWR_ON HIGH

EXTENDED

UNDERVOLTAGE

(FAULT)

WAKE

250μs

Figure 13. Initial Power-Up and LDO1 Undervoltage RSTO Timing

RSTO Pin Function

The RSTO (reset output) pin is an open-drain output for use

as a power-on reset signal. It is pulled LOW at initial power

until LDO1 is within 8% of its target and the initial one second

start-uptimerisfinished.RSTOremainsHIGHduringnormal

operation and will be pulled low if LDO1 loses regulation for

more than 25μs or a pushbutton hard reset is initiated. RSTO

is released high 14ms after LDO1 returns to regulation.

Figure 13 shows a initial power-up for the RSTO pin. If VIN

is not above its undervoltage thresholds at the end of the 1

second start-up time, the IRQ pin will be pulled LOW and an

undervoltage bit will be set in the IRQSTAT status register.

voltage for longer than 25μs (typical), the PGOOD pin is

pulled LOW and the appropriate bit in the PGSTAT status

Table 15. PGSTAT Read-Only Register Bit Definitions

PGSTAT[BIT] VALUE

SETTING

LDO1_STBY Output Low

LDO1_STBY Output Good

Step-Down Switching Regulator 1 Output Low

Step-Down Switching Regulator 1 Output Good

Step-Down Switching Regulator 2 Output Low

Step-Down Switching Regulator 2 Output Good

Step-Down Switching Regulator 3 Output Low

Step-Down Switching Regulator 3 Output Good

Buck-Boost Regulator 4 Output Low

Buck-Boost Regulator 4 Output Good

LDO2 Output Low

LDO2 Output Good

LDO3 Output Low

LDO3 Output Good

LDO4 Output Low

LDO4 Output Good

Figure 14 shows the PGOOD pin and PGSTAT status reg-

ister timing. When no regulator is enabled, the PGOOD

pin is pulled LOW and PGSTAT bits are LOW. PGOOD and

the PGSTAT bits are HIGH 250μs after the last enabled

regulator is within 7% of its target.

PGOOD Pin and PGSTAT Status Register Function

Each LTC3589 regulator has an internal power good out-

put that is active whenever the regulators feedback pin is

closer than 7% (typical) from its input reference voltage.

If any of the internal power good signals indicate a low

OPERATION

LDO1

RSTO

VIN 2.7V

–8%

1 SEC

INITIAL POWER-UP

LTC3589

LDO1 UNDERVOLTAGE

25μs

14ms

3589 F13

LDO1

RSTO

VIN

–8%

INITIAL POWER-UP

LTC3589-1/LTC3589-2

LDO1 UNDERVOLTAGE

25μs

14ms

LTC3589 Datasheet(PDF) 33 Page - Linear Technology

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