DS3984Z datasheet(16/24 Pages) DALLAS

16 / 24 page

4-Channel Cold-Cathode

Fluorescent Lamp Controller

____________________________________________________________________

Detailed Register Descriptions

The DS3984’s Register Map is shown in Table 1.

Detailed register and bit descriptions follow in the sub-

sequent tables.

Soft-Start Profile (SSPx) Registers—Each of the four

soft-start profile registers (SSP1–4) contains two 4-bit

codes that determine the MOSFET’s duty cycle (MDC)

for two clock cycles each (see Figure 6) at the begin-

ning of each DPWM burst. Table 2 shows the duty

cycles that correspond to each code. Selecting the

Most Recent Value instructs the DS3984 to use the

MOSFET duty cycle that was used for the last lamp

cycle of the previous burst.

BYTE

ADDRESS

BYTE

NAME

FACTORY

DEFAULT*

BIT 7

BIT 6

BIT 5

BIT 4

BIT 3

BIT 2

BIT 1

BIT 0

F0h

SSP1

21h

MDC code for soft-start lamp cycles 3, 4

MDC code for soft-start lamp cycles 1, 2

F1h

SSP2

43h

MDC code for soft-start lamp cycles 7, 8

MDC code for soft-start lamp cycles 5, 6

F2h

SSP3

65h

MDC code for soft-start lamp cycles 11, 12

MDC code for soft-start lamp cycles 9, 10

F3h

SSP4

77h

MDC code for soft-start lamp cycles 15, 16

MDC code for soft-start lamp cycles 13, 14

F4h

CR1

00h

DPD

FRS

ARD

RGSO

DPSS

LFSS

POSCS

LOC

F5h

CR2

08h

LD2

LD1

LD0

LSR1

LSR0

POSCR1

POSCR0

UMWP

F6h

CR3

00h

Do not modify. If it has been modified, restore to all zeros.

F7h

Reserved

——

———

—

F8-FFh

User

Memory

00h

*All the configuration settings are saved in nonvolatile (EEPROM) memory.

Table 1. Register Map

Table 2. MOSFET Duty Cycle (MDC)

Codes for Soft-Start Settings

MDC CODE (BINARY)*

MOSFET DUTY CYCLE

X000

Fixed at 0%

X001

Fixed at 3%

X010

Fixed at 6%

X011

Fixed at 9%

X100

Fixed at 13%

X101

Fixed at 16%

X110

Fixed at 19%

X111

Most Recent Value

*The most significant bit of each MDC code is ignored.

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