SM8613 Nippon_Precision_Circuits America, SM8613 Datasheet - Page 6

• Manufacturer Part Number: SM8613
• Description: CD Laser Driver
• Manufacturer: Nippon_Precision_Circuits America

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.
Table 1. Control signals and laser drive states
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
the duty ratio almost constant. The intermittent current duty ratio is set by resistor R
DUTY and VSS pins, and is given by the following equation.
LDON
H
H
H
H
L
dutyratio =
V(DUTY) =
I(LDIOUT)
PLSON
PCK
H
H
×
L
L
1−
R
DUTY
3
2
MUTE
V(DUTY)
1
2
H
H
L
L
×
R
VDD
DUTY
+ 44[kΩ]
LDIOUT constant-current output
LDIOUT constant-current output
LDIOUT intermittent current output
LDIOUT constant-current output
LDIOUT = 0mA (sleep mode)
a
× 100 =
b
SM8613AV
× VDD [V]
Laser drive state
duty ratio (a/b) control
44[kΩ] − 2 × R
R
DUTY
+ 44[kΩ]
NIPPON PRECISION CIRCUITS INC.—6
R
DUTY
DUTY
: resistor connected to DUTY pin [kΩ]
DUTY
× 100 [%]
large current
connected between
time