SM8613 Nippon_Precision_Circuits America, SM8613 Datasheet - Page 7

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

Laser Diode Drive Current Mid-value Set Function
The laser diode drive current mid-value can be adjusted by changing the resistance R
LDISET and VSS pins. The laser diode drive current mid-value reference value I
equation, is set to the LDIOUT output current when the PDVIN voltage is in balance state (147 to 193mV).
Note that the actual LDIOUT current may change due to feedback gain, and laser diode/photo diode tolerance
variations.
If R
by the PDVIN convergence voltage.
APC Loop Gain Setting
The APC loop gain can be adjusted using an external resistor R
between RGAIN and CGAIN. The PDVIN voltage to laser drive current open-loop gain is given approximately
by the following equation.
If the external resistor R
APC Loop Cutoff Frequency Setting
The APC loop cutoff frequency f
pins. The same result occurs if C
G
is not connected, the output current has no relationship to the reference current value, but is determined
G
is removed, the maximum gain Gm = 26 [S] is selected.
G
APC
I
is connected between RGAIN and CGAIN pins.
LD0
Gm
is determined by the capacitor C
= I
f
APC
PDVIN
LDSET
=
= 1.15 × 10
× 120 =
SM8613AV
2π950C
1
G
40VDD
−4
R
R
[Hz]
LD
G
G
. The gain set resistor, R
[S]
G
[A]
connected between CGAIN and VSS
NIPPON PRECISION CIRCUITS INC.—7
∆LDIOUT current /∆PDVIN voltage ratio [S]
LD0
R
LD
LD
, given by the following
: LDISET connected resistor [Ω]
R
connected between the
G
: RGAIN–CGAIN resistor [Ω]
G
, is connected