LP3972 datasheet(32/59 Pages) TI1

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LP3972

SNVS468J – SEPTEMBER 2006 – REVISED AUGUST 2011

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NSC DEFINED CONTROL AND STATUS REGISTERS

SYSTEM CONTROL REGISTER 1 (SCR1)

System Control Register 1 (SCR1) 8h’80

Bit

7(1)

6(1)

5(1)

Designation

BPSEN

SENDL

FPWM3

FPWM2

FPWM1

BK_SLOMOD

BK_SSEN

Reset Value

(1)

One-time factory programmable EPROM registers for default values

System Control Register 1 (SCR1) 8h’80 Definitions

Bit

Access

Name

Description

R/W

BPSEN

Bypass System enable safety Lock. Prevents activation of PWR_EN

when SYS_EN is low.

0 = PWR_EN "AND" with SYS_EN signal, Default

1 = PWR_EN independent of SYS_EN

Delay time for High Voltage Power Domains LDO2, LDO3, LDO4,

Buck2, and Buck3 after activation of SYS_EN. VCC_LDO1 has no

delay.

Data Code

Delay (ms)

6:5

R/W

SENDL

2h’0

0.0

2h’1

0.5

2h’2

1.0 (Default)

2h’3

1.4

R/W

FPWM3

Buck3 PWM/PFM Mode select

0 - Auto Switch between PFM and PWM operation

1 - PWM Mode Only will not switch to PFM

R/W

FPWM2

Buck2 PWM/PFM Mode select

0 - Auto Switch between PFM and PWM operation

1 - PWM Mode Only will not switch to PFM

R/W

FPWM1

Buck1 PWM/PFM Mode select

0 - Auto Switch between PFM and PWM operation

1 - PWM Mode Only will not switch to PFM

BK_SLOMOD

Buck Spread Spectrum Modulation Bucks 1-3

0 = 10 kHz triangular wave spread spectrum modulation

1 = 2 kHz triangular wave spread spectrum modulation

BK_SSEN

Spread spectrum function Bucks 1-3

0 = SS Output Disabled

1 = SS Output Enabled

SYSTEM CONTROL REGISTER 2 (SCR2)

System Control Register 2 (SCR2) 8h’81

Bit

5(1)

Designation

BBCS

SHBU

BPTR

WUP3

GPIO2

GPIO1

(1)

One time factory programmable EPROM registers for default values

System Control Register 2 (SCR2) 8h’81 Definitions

Bit

Access

Name

Description

R/W

BBCS

Sets GPIO1 as control input for Back Up battery charger

0 - Back Up battery Charger GPIO Disabled

1 - Back Up battery Charger GPIO Pin Enabled

Shut down Back up battery to prevent battery drain during shipping

R/W

SHBU

0 = Back up Battery Enabled

1 = Back up battery Disabled

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