ELM185xB Laser Diode Driver
Typical Electric characteristics of LDM
table 1
Unit
Parameter
Action current
Monitor current
Symbol
Iop
Min.
-
Typ.
35
Max.
50
mA
mA
Im
0.05
0.10
0.30
Recommendation of absolute ratings of each circuit when using the LDM of table 1
Recommended absolute
table 2
No.
parts
Notes
ratings
R1 *1
fixed resistor
adjustable resistor
fixed resistor
1.0kΩ
LD output adjustment
LD output adjustment
VR1 *2
R2 *3
C1
5.0kΩ
3.3Ω
current limit setting (no limit under 0Ω)
control loop stabilization
ceramic capacitor
electrolysis, ceramic, etc.
PNP transistor
3300pF
1μF to 100μF
C2
power stabilization
Tr1 Tr2
small signal transistor monitor current mirror circuit
1 R1=0.3/ Im (Max.)
2 (R1 + VR1) = 0.3/ Im (Min.)
3 R2=0.15/ Iop (Max.)
*
*
*
■Application circuit example 2 (Pulse drive circuit)
For application circuit of intermittent diode output controlled by external signal, please refer to application
circuit (4).
Max. frequency can set to be on/off by limit of response speed of laser diode output control loop is 20kHz.By
using logic gate, the control of on/off is easy; it is required that the resistances of R1, R3 and VR1 are much
larger than the output resistance of logic gate.
circuit (4)
C2
D2
D1
LD
MD
LDM
V1
VCC
KLD
CMP
ILM
C1
R2
ELM185xB
AMD
VR1
R1
GND
R3
Pulse in
For pulse drive, please add resister to AMD pin in circuit (1) to control signal of pulse drive.
Adjustable resistor (VR1) is inserted in the place as shown above in order to adjust monitor current; pulse
drive control signal shall be added between R1 and VR1.
*
*
R3: resistor of the input of pulse drive control signal. VCC is set to be higher than Vamd=0.30V(Typ.)
*
*
VCC R1 / (R3 + R1) > Vamd
*
e.g.) when VCC=3.3V, R1=1kΩ, R3 < R1 (VCC-Vamd)/Vamd = 1kΩ (3.3-0.3)/0.3 = 10kΩ.
*
*
The control signal is logic level; laser light will be switched off when the signal is H and switched on when it
is L.
10 - 6
ELM-TECH [ ELM Technology Corporation ]
