LP3910 Datasheet, PDF(58/72 Page) Texas Instruments – Power Management IC for Hard-Drive-Based Portable Media Players

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LP3910 Datasheet, PDF (58/72 Pages) Texas Instruments – Power Management IC for Hard-Drive-Based Portable Media Players

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LP3910

SNVS481M â NOVEMBER 2006 â REVISED DECEMBER 2015

www.ti.com

8.6.13 Buck1, Buck2 Control Registers and BUCK1EN Pin

Buck1 and Buck2 are configurable through I2C accessible registers. Bit fields D4â0 control the output voltage. Bit

D5 defines the Modulation mode of the buck, which by default automatically selects PWM or PFM mode

depending on the load as described above in the functional description. The modulation mode can be forced to

PWM mode regardless of the load by setting bit D5 to a logic 1 in the corresponding buck control register.

Bit D6 controls the enable/disable state of the buck, which is different for Buck1 and Buck2 as Buck1 has an

external enable pin: BUCK1EN.

For Buck1, by default or when D6 is programmed logic 0 in the Buck1 control register, enable/disable control is

passed onto the BUCK1EN pin. A logic 1 applied to this pin enables Buck1 while a logic 0 disables Buck1.

Setting D6 to 1 in the Buck1 control register enables BUCK1, regardless of the state of the BUCK1EN pin. If the

system designer permanently connects the BUCK1EN pin to GND, then D6 is simply a enable/disable control bit.

If the system design permanently connects the enable pin to VDD, then the Buck1 is enabled during the power-on

sequence and is always be on, regardless of the state of bit D6 in the Buck1 control register (see Power-On,

Power-Off Sequencing).

BUCK2 is by default enabled during the power-on sequence and can be enabled/disabled through bit D6 in the

Buck2 control register.

Access

Data

Reset

Read Only 0

Reserved

Table 12. Buck1 Control Register (05)H

Operation

0: enable/disable

determined by state of

BUCK1EN pin

1: enable, override

BUCK1EN state

R/W

Force PWM mode

0: Automatic Modulation

Mode

1: Force PWM mode

n/a

D4â0

BUCK1 Output Voltage (V)

5âh00

Externally

controlled

5âh01

0.80

5âh02

0.85

5âh03

0.90

5âh04

0.95

5âh05

1.00

5âh06

1.05

5âh07

1.10

5âh08

1.15

5âh09

1.20

5âh0A

1.25

5âh0B

1.30

5âh0C

1.35

5âh0D

1.40

5âh0E

1.45

5âh0F

1.50

5âh10

1.55

5âh11

1.60

5âh12

1.65

5âh13

1.70

5âh14

1.75

5âh15

1.80

5âh16

1.85

5âh17

1.90

5âh18

1.95

5âh19â1F

2.00

Factory-Programmed Default

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