SM8613AV

NIPPON PRECISION CIRCUITS INC.—6

FUNCTIONAL DESCRIPTION

LD Driver Control

The LD is controlled by the 3 logic-level signals on LDON, PLSON, and MUTE. When LDON is HIGH, the

LD is in drive mode and the drive current is output on LDIOUT. When LDON is LOW (sleep mode), the LD

drive mode stops (LDIOUT output current = 0mA).

Also when LDON is HIGH, LD intermittent drive mode operation occurs when PLSON is HIGH and MUTE is

LOW.

Note)

× : Don’t care.

Frequency Multiplier Function and LD Drive Current Duty Ratio Setting

The SM8613AV multiplies the PCK input frequency by 2, which is then used as the intermittent-drive refer-

ence frequency. The intermittent drive LD current ON time is shown in the following figure.

The intermittent current output from LDIOUT is automatically adjusted as the frequency changes to maintain

DUTY and VSS pins, and is given by the following equation.

Table 1. Control signals and laser drive states

LDON

PLSON

MUTE

Laser drive state

H

L

L

LDIOUT constant-current output

H

L

H

LDIOUT constant-current output

H

H

L

LDIOUT intermittent current output

H

H

H

LDIOUT constant-current output

L

××

LDIOUT = 0mA (sleep mode)

PCK

a

I(LDIOUT)

b

duty ratio (a/b) control

large current

time

dutyratio =

V(DUTY)

3

2

1

−

VDD

1

2

× 100 =

Ω]

44[k

V(DUTY) =

Ω]

× VDD [V]