ELM ELM185 Laser diode driver Datasheet

ELM185xB Laser Diode Driver
■General description
ELM185xB is a bipolar type laser diode driver IC with internal APC circuit which consists of a reference
voltage source, an error amplifier, and a thermal shutdown circuit for protection. With reference voltage source,
the output of laser is comparatively stable during the change of power voltage and temperature. With its small
package, ELM185xB is possible to be assembled within small areas on the board. When control loop damage
occurs, ELM185xB is also capable of limiting the laser drive current; limited current value can be adjusted by
an external resister on ILM. KLD output drive current can reach up to 400mA (max.). For avoidance of damage
of laser diode, the Zener diode which is included in ELM185xB is able to absorb 8V surge between VCC-GND.
ELM185xB is able to drive various types of laser diode modules (LDM); please refer to applicable laser
diode modules for further information. ELM185xB can not only drive laser diode by APC control, but also
by constant current with internal constant current setup function; therefore, ELM185xB can also be used as
constant current driver for laser diode, high luminous LED, etc.
■Features
•
•
•
•
•
•
•
Low voltage operation
: 2.0V
Low current consumption operation : Typ.1mA
Laser drive current
: Max.400mA
Internal voltage reference
: Typ.0.30V
Thermal shutdown circuit
: Typ.150°C
Package
: SOT-26, VSON6-2x2
Zener diode for surge absorption included
■Application
• Driver for laser diode in laser pointer, laser level, etc.
• Driver for constant load current such as LED, etc.
■Maximum absolute ratings
Parameter
Symbol
Limit
Unit
Operation voltage
CMP voltage
ILM voltage
VCC
GND-0.3 to 7.0
V
Vcmp
Vilm
GND-0.3 to 7.0
GND-0.3 to 7.0
V
V
KLD voltage
AMD voltage
KLD current
Vkld
Vamd
Ikld
GND-0.3 to 18.0
GND-0.3 to VCC+0.3
500
Power dissipation
Operation temperature
Storage temperature
300 (SOT-26)
Pd
1000 (VSON6-2x2)
-30 to +85
-40 to +125
Top
Tstg
10 - 1
V
V
mA
mW
°C
°C
Rev.1.0
ELM185xB
Laser Diode Driver
■Selection guide
ELM185xB-S
Symbol
ELM185 x B - S
↑ ↑ ↑
a b c
B: SOT-26,
G: VSON6-2x2
a
Package
b
Product version
B
c
Taping direction
S: Refer to PKG file
■Pin configuration
SOT-26(TOP VIEW)
6
5
1
Pin No.
Pin Name
1
2
AMD
GND
3
4
5
CMP
ILM
VCC
6
KLD
4
2
3
VSON6-2x2(TOP VIEW)
6
5
4
4
5
6
Pin No.
1
2
3
3
VSON6-2x2(BOTTOM VIEW)
6
5
4
4
5
6
1
2
3
3
2
1
10 - 2
2
Pin Name
11
KLD
2
3
VCC
ILM
4
5
6
CMP
GND
AMD
Rev.1.0
ELM185xB
Laser Diode Driver
■Block diagram
VCC
KLD
CMP
GND
Pin description
Pin
AMD
CMP
ILM
KLD
VCC
GND
+
-
AMD
CONTROL
AMP
VREF
ILD
CURRENT
LIMIT CMP
DRIVER
CONTROL
+
-
LD monitor input
ILM
VREF
LIMIT
Name
DRIVER
NPN TR
Content
connected to anode of monitoring diode
phase compensation input of phase compensation capacitor for control feedback loop stabilization
LD current limit input of detection of laser diode driver drive current limit
LD drive output
power output
ground
connected to cathode of laser diode
power input of IC
ground of IC
Description :
The internal APC circuit of ELM185xB controls the output of laser oscillation at constant value with the
feedback of monitor photo diode light output current. Monitor photo diode light current will be changed to
voltage by resistance and becomes the input of AMD; this voltage is set to be 0.3V, which is the same as the
reference voltage inside IC. It is possible to acquire constant laser output by the laser diode drive current which
is controlled by this voltage; hence, laser light output can be adjusted by the resistor connected to AMD.
Laser diode drive current can be changed to voltage by resistance connected to ILM, and the increase of this
voltage is limited under current limit voltage (Typ.0.15V). ILM is also capable of avoiding the damage of
overmuch drive current of laser diode which is caused by control loop abnormality.
For stability of control return loop, a phase compensation capacitor is required to be connected to CMP. Please
set to small value at least above 3nF when making ON/OFF control with fast speed.
Laser diode is driven by the open collector output of NPN transistor inside ELM185xB; therefore, drive current
(Max.18V) higher than power voltage of IC can be added as drive voltage of laser diode. ELM recommends
inserting resistance between laser diode module (LDM) and KLD if the drive voltage is high so as to disperse
power loss.
By monitor current detection function of ELM185xB, AMD can be used as ON/OFF control pin. It is also
possible to control switching of laser diode when the input source is from external control signal; the ON/OFF
control will become 0.3V threshold voltage.
By 7V voltage, the Zener diode between power and ground of ELM185xB is able to absorb power surge;
meanwhile, the Zener diode is also capable of decreasing the damage of surge by clipping the surge voltage of
power line.
10 - 3
Rev.1.0
ELM185xB
Laser Diode Driver
■Electrical characteristics
Parameter
Operation voltage
Symbol
VCC
Current consumption
ICC
Vamd
AMDreference voltage
Condition
Min.
2.0
VCC=3.6V
VCC=3.6V
0.285
Vamd temperature
characteristics
ΔVamd
ΔTop
KLD current
KLD leak current
IDkld
ILkld
VCC=2.7V, Vkld=1.0V
VCC=5.5V
400
ILM current limit voltage
Vilm
VCC=3.6V
0.13
Max. external clock frequency
AMD input current
Fext
Iamd
VCC=3.6V
VCC=5.5V, Vamd=1.0V
Zener diode avalanche voltage
ZDBV
VCC=3.6V
Typ.
Max.
6.5
Unit
V
1
3
mA
0.300
0.315
V
±200
ppm/°C
1.0
mA
μA
0.17
V
-0.5
20
0.5
kHz
μA
6.8
8.0
V
0.15
■Marking
SOT-26
a b c d
�
Symbol
Mark
Content
a, b, c
2NW
Series : 185
Package : SOT-26
d
0 to 9 and
A to Z ( I, O, X excepted)
Assembly lot No.
Symbol
185
Mark
185
Content
185 series
a, b, c
0 to 9 and
A to Z ( I, O, X excepted)
Assembly lot No.
VSON6-2x2
1 8 5
a b c
10 - 4
Rev.1.0
ELM185xB
Laser Diode Driver
■Application circuit example 1 (continuous drive circuit)
Circuit that laser diode is driven by constant output continuously. LDM, which is the combination of laser
diode (LD) and monitor diode (MD), is commonly used.
Based on various ways of handling poles and common pins, there are many different types of internal wire
of anode and cathode of LDM. Examples which LDM can be easily connected to ELM185xB are shown as
following three application circuits.
The fittest value of circuit constants will be different according to the used laser diode. Table 2 shows the
example when the forward current of laser diode is 35mA and monitor diode light current is 0.1μA.
circuit (1)
V1
D2
D1
MD
LD
C2
LDM
VCC
KLD
CMP
C1
ELM185xB
AMD
ILM
GND
VR1
R2
R1
circuit (2)
V1
D2
D1
MD
LD
C2
VCC
LDM
CMP
KLD
C1
ELM185xB
ILM
AMD
GND
VR1
R2
R1
circuit (3)
Tr2
Tr1
D2
D1
MD
LD
V1
C2
VCC
LDM
KLD
CMP
C1
ELM185xB
AMD
ILM
GND
VR1
R2
R1
10 - 5
Rev.1.0
ELM185xB
Laser Diode Driver
Typical Electric characteristics of LDM
Parameter
Symbol
Action current
Iop
Min.
-
Typ.
35
Max.
50
table 1
Unit
mA
Monitor current
0.05
0.10
0.30
mA
Im
Recommendation of absolute ratings of each circuit when using the LDM of table 1
Recommended absolute
No.
parts
Notes
ratings
R1 *1
fixed resistor
1.0kΩ
LD output adjustment
VR1 *2
R2 *3
C1
adjustable resistor
fixed resistor
ceramic capacitor
5.0kΩ
3.3Ω
3300pF
C2
Tr1 Tr2
electrolysis, ceramic, etc.
PNP transistor
1μF to 100μF
small signal transistor
table 2
LD output adjustment
current limit setting (no limit under 0Ω)
control loop stabilization
power stabilization
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)
V1
D2
D1
MD
LDM
LD
C2
VCC
KLD
AMD
R3
Pulse in
VR1
CMP
C1
ELM185xB
ILM
GND
R2
R1
* 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
Rev.1.0
ELM185xB
Laser Diode Driver
• Pulse drive wave
This drive wave is tested base upon standard circuit (4) under the conditions that R1=22kΩ, R2=2.2Ω,
R3=220kΩ, VR1=0, C1=3300pF, C2=1μF, V1=3.6V
ch3
ILM wave= current wave
ch2
AMD wave
ch1
control signal pulse in
Ch1 2.00V/div
Ch2 500mV/div
Ch3 100mV/div
50.0μs/div
■Application circuit example 3 (Drive circuit with detection circuit of single fault mode)
Based on different applications of laser, it is required that laser output can be maintained in safety region when
single fault error happens. The example of single fault detection circuit is shown as application circuit (5).
If any of following 3 conditions happens, laser output of ELM185xB will be overmuch when single fault of all
pin occurs:
1) Ground short fault happens to KLD (Ground current will be flowed directly from laser and thus result in
overmuch of laser diode light output.)
2) Ground short fault happens to AMD (laser diode light output will be overmuch since output is judged to be 0)
3) VCC short fault happens to CMP (laser diode light output will be overmuch since circuit cannot be controlled.)
If any of these 3 conditions is detected, laser drive will be stopped forcibly and become single fault detection
circuit. Meanwhile, the condition when single fault occurs is the same as initial power input, solutions (start-up
circuit) of error detection for normal action when the circuit starts is required additionally.
For example of this safety circuit, please refer to application (5).When abnormality occurs, ELM742B, the
comparator will detect the error, the latch which is composed by ELM7SU04BW will be turned reversely,
and ELM33405CA, P-ch MOS will be off and thus shut down the power. When comparison voltage of
3 comparators is under 0.9V of KLD, under 0.1V of AMD, and above 2.5V of CMP, it will be judged as
abnormality by OR condition of the comparator and thus the power will be shut down. This circuit is only for
reference use; confirmation of safety standard fit actions on actual application is still required.
Start-up circuit consists of time constant of R1 and C1.The ratio of disperse voltage of R3, R4, R5, R8 is
required to be changed with power voltage. For best solution, ELM recommends using ELM742B as the
voltage detector, ELM7SU04BW as the latch and ELM33405CA as the transistor.
This circuit is for reference use only; additional inspection of safety standard suitableness is required.
It is possible to insert detection circuit as shown in circuit (2) and (3) in this circuit.
10 - 7
Rev.1.0
ELM185xB
Laser Diode Driver
circuit (5)
+ V1
ELM7SU04BW
A2
ELM33405CA
5V
ELM742B
R2
100k
R1
100k A1
M1
U1
U2
C1
0.1�
C3
10�
D2
D1
MD
LD
U3
+
R3
100k
+
R4
68k
+
R8
33k
2.5V
0.9V
0.1V
R5
2.2k
VCC
KLD
ELM185xB
AMD
R6
3k
GND
CMP
ILM
R7
2.2
C2
3300p
■Application circuit example 4 (white LED constant current drive circuit)
Example of application of ELM185xBA as LED constant current drive current is shown as circuit (6).
This circuit is white LED drive circuit which is driven by constant current with external resistance of ILM.
Since the voltage limit of KLD can reach 18V, it is possible to design several LEDs in series connection. The
VCC voltage is controlled to be constant by internal Zener diode of ELM185xB.
circuit (6)
+ V1
12V
White LED
R1
4.7k C1
D3
D2
1�
D1
VCC
KLD
R2
100k
W1
Switch
ELM185xB
AMD
GND
ILM
R7
4.7�
CMP
C2
10n
This circuit is designed by 3 series-connected white LEDs with power of 12V.
In this circuit, AMD is not used to control light feedback, but on/off only. Current control, which is constant
current type, is monitored by the voltage of ILM. Capacitors of 0.1μF-0.01μF for anti-oscillation are connected
to CMP. Resistance of R7 is set by constant current value; it will be 34mA under 4.7Ω. This value is calculated
by the formula that Iout=0.16/R7. The power of ELM185xB will be lowered from 12V to 7V by R1 and internal
Zener. Light will be turned on when the switch of W1 is ON, and be off when it is OFF.
10 - 8
Rev.1.0
ELM185xB
Laser Diode Driver
■Notice
1. Safety standard
For different applications of laser diode, it is sometimes required that the application should obey the safety
standard which is ruled by the law. Please make complete confirmation about which safety or law should be
obeyed while designing the circuit. ELM185xB drives laser diode by the conditions which is set by external
circuit; please confirm the actual output of light by instruments such as light power meter.
2. Laser diode damaged caused by surge voltage
Laser diode can be easily damaged by static or surge voltage when the power is turned on/off because of its low
surge resistance. ELM185xB includes Zener for absorption of surge; for best protection, ELM recommends
connecting ELM185xB and laser diode in the shortest distance.
connection in shortest distance
LD
K
A
6
5
4
KLD
VCC
ILM
ELM185xB
AMD
GND
CMP
1
2
3
■Applicable laser diode modules
Type 1
1 : LD cathode
2 : LD anode, MD cathode
3 : MD anode
Type 2
1 : LD anode
2 : LD cathode, MDcathode
3 : MD anode
Type 3
1 : LD anode
2 : LD cathode, MD anode
3 : MD cathode
It is possible to connect separate LD and MD to ELM185xB.
When connecting different LDMs other than these 3 types, additional parts are required.
10 - 9
Rev.1.0
ELM185xB
Laser Diode Driver
■Electrical characteristics
1. Icc consumption current
characteristics of power voltage vs.
consumption current
Icc
A
Vcc vs Icc
4
3
Icc (mA)
Icc consumption current test circuit
85�
Vcc V
2
5
4
KLD
VCC
ILM
ELM185xB
25�
-30�
1
0
0
6
Vcc (V)
GND
CMP
1
2
3
0.1��
10
8
6
4
2
AMD
2. Vamd standard voltage
power voltage vs. AMD standard voltage
Vcc -Vamd
0.35
Vamd (V)
Vamd standard voltage test circuit
0.3
5
4
KLD
VCC
ILM
ELM185xB
0.25
0.2
6
85�
-30�
25�
AMD
GND
CMP
1
2
3
Vamd V
4
2
Vcc (V)
8
6
3. Ikld constant current
KLD output current voltage characteristics
Ikld constant current test circuit
Ikld
A
Vkld - Ikld
160
Ikld (mA)
140
120
100
1�
2.2�
80
Vkld V
4.7�
60
5.0V
6
5
4
KLD
VCC
ILM
RILM
ELM185xB
40
AMD
GND
CMP
20
1
2
3
0
0
5
Vkld (V)
10
0.1��
15
* When Vkld, Ikld are large, protection circuit operates according to the heat generation of IC;
the limit will be determined by heat characteristic of actual assembly.
10 - 10
Rev.1.0