4-Channel Cold-Cathode

Fluorescent Lamp Controller

18

____________________________________________________________________

Table 4. Control Register 2 (CR2)

BIT

NAME

FUNCTION

0

UMWP

User Memory Write Protect.

0 = User Memory Write Access Blocked

1 = User Memory Write Access Permitted

1

POSCR0

DPWM Oscillator Range Select. When using an external source for the dimming clock, these bits must

be set to match the external oscillator’s frequency. When using a resistor to set the dimming

frequency, these bits plus the external resistor control the frequency.

POSCR1

POSCR0

DIMMING CLOCK (DPWM)

FREQUENCY RANGE (Hz)

K

(k

Ω-kHz)

00

22.5 to 55.0

1

01

45 to 110

2

10

90 to 220

4

2

POSCR1

11

180 to 440

8

Lamp Sample Rate Select. Determines the feedback sample rate of the LCM inputs.

LSR1

LSR0

SELECTED LAMP

SAMPLE RATE

EXAMPLE SAMPLE RATE

IF LAMP FREQUENCY IS

50kHz

3

LSR0

00

4 Lamp Frequency Cycles

12500Hz

01

8 Lamp Frequency Cycles

6250Hz

10

16 Lamp Frequency Cycles

3125Hz

4

LSR1

11

32 Lamp Frequency Cycles

1563Hz

Lamp Disable. Used to disable channels if all 4 are not required for an application.

LD1

LD0

CHANNELS DISABLED

NUMBER OF ACTIVE

LAMP CHANNELS

00

All Channels Enabled

4

5

LD0

01

4

3

10

2/4

2

6

LD1

11

1/2/4

1

7

Reserved

Reserved. Should be set to zero.