DS3988 Datasheet, PDF (16/23 Pages) Maxim Integrated Products – 8-Channel Cold-Cathode Fluorescent Lamp Controller

8-Channel Cold-Cathode
Fluorescent Lamp Controller
Detailed Register Descriptions
The DS3988’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 DS3988 to use the
MOSFET duty cycle that was used for the last lamp
cycle of the previous burst.
Table 2. MOSFET Duty Cycle (MDC)
Codes for Soft-Start Settings
MDC CODE (BINARY)*
X000
MOSFET DUTY CYCLE
Fixed at 0%
X001
X010
Fixed at 3%
Fixed at 6%
X011
X100
X101
Fixed at 9%
Fixed at 13%
Fixed at 16%
X110
X111
Fixed at 19%
Most Recent Value
*The most significant bit of each MDC code is ignored.
Table 1. Register Map
BYTE
BYTE
ADDRESS 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
00h
Memory
EE
EE
EE
EE
EE
EE
EE
EE
*All the configuration settings are saved in nonvolatile (EEPROM) memory.
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