| 1 | CX1 | These pins are provided for connecting an external capacitor to the control loop integrator to extend the integrator time constant. This may necessary to get maximum bandwidth when using TTL modulation. Connect the positive terminal of the cap to CX2. |
| 2 | CX2 |
| 3 | Analog Modulation | This pin is used with an external voltage signal source to provide analog modulation. The transfer function (referenced to the photodiode current) is -50μA/V (see note 1) with 0V being the laser completely on. The laser output decreases as this voltage increases with the laser being completely off at 2.5V. Connect this pin to ground when not using the analog modulation. |
| 4 | Slow Start | This output pin is high during the start up period and goes low when the laser is enabled. It can be used as a LASER EMISSION indicator. An external capacitor can be connected from this pin to ground to extend the slow start delay time. Note: this output will not drive an LED directly and must be buffered (contact the factory for more details). |
| 5 | PD Current Trimpot | This pin is connected to the wiper of the on-board PD Current Trimpot. Connect this pin to the PD Current Setpoint to control the photodiode current with the on-board trimpot. |
| 6 | PD Current Setpoint | This pin controls the PD Current according to a transfer function of 50μA/V with 0V being the laser is completely off (0 photodiode current). The laser output increases as this voltage increases. |
| 7 | REF Out | This is a buffered 2.5V voltage reference. |
| 8 | PD AMP Out | This is an analog voltage proportional to the photodiode current and referenced to one half the supply voltage. |
| 9 | +V | Positive supply voltage (+8 to +12VDC). |
| 10 | Ground | Power supply common. |
| 11 | LD A/PD K | Common laser diode anode, photodiode cathode. |
| 12 | PD A | Photodiode anode. |
| 13 | LD K | Laser diode cathode. |
| 14 | Limit Setpoint | This voltage determines the maximum laser drive current according to the transfer function 46mA/V. |
| 15 | Limit Trimpot | This is connected to the wiper of the Limit Current trimpot. Connect this to the Limit Setpoint pin to use the on-board trimpot to set the current limit. |
| 16 | Not Used | This must be tied to ground to operate the laser. |
| 17 | On/Off | This pin is used to externally turn the laser on and off through the slow start circuit and to set the low voltage dropout point. It has an internal 20kΩ resistor to ground. Connect a 15KΩ resistor to the power supply voltage to set the dropout voltage to 4.5V. |
| 18 | Limit Out | This is an output voltage proportional to the limit current with a transfer function of 40mA/V. Use this pin to assist in setting the laser current limit. |
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Constant Power LD Controller
