SM8610CV Datasheet, PDF (7/9 Pages) Nippon Precision Circuits Inc – Laser Switching Driver IC

SM8610CV
Laser Diode Drive Current Mid-value Set Function
The laser diode drive current mid-value can be adjusted by changing the resistance R_LD connected between the
LDISET and GND pins. The laser diode drive current mid-value base value I_LDSET, given by the following
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 variations.
ILDSET = ILDSET × 1000 = ^800[V] [A]
RLD
APC Loop Gain Setting
R_LD : LDISET connected resistance [Ω]
The APC (Auto Power Control) loop gain can be adjusted by changing the external gain set resistance (R_G)
connected between the RG1 and RG2 pins. The PDVIN voltage-to-laser drive current open-loop gain is given
approximately by the following equation.
GmPDVIN = 9.1 × 10 ^−5 RG [S]
APC Loop Cutoff Frequency Setting
∆LDIOUT current /∆PDVIN voltage ratio [S]
R_G : Resistance connected between RG1 and RG2 [Ω]
The APC loop cutoff frequency fc is determined by the external resistance R_G and the capacitance C_G, con-
nected between RG1 and RG2.
fC1 =
1
2πRGCG
[Hz]
If C_G is connected between RG2 and VCC, the cutoff frequency is given as follows.
fC2 =
1
[Hz]
2√2πRGCG
NIPPON PRECISION CIRCUITS INC.—7