Rev. 01/2021
11
Pulser OK (Pin 1)
This signal informs the user about any error condition. It is pulled low by the driver when no
internal error is detected (remark: The word “pulser” here refers to the “driver” itself).
Functional Description
The driver operates with four parallel buck converters (S1, S2, D1, D2, L1; S3, S4, D3, D4,
L2; S5, S6, D5, D6, L3; S7, S8, D7, D8, L4). Every single converter has an independent
control loop with a current sensor (Imeas1, Imeas2, Imeas3 and Imeas4). The setpoint current
that is defined by the user is evenly spread over all four converters. The current through the
laser diode is measured directly at the output pins with the help of a shunt resistor.
Inductor current (additional current of all three phases), laser diode current and compliance
voltage are pre-processed and then fed into to the external BOB connector. An enable input as
well as a status output is available.
Several security features protect the laser diode and driver from damage. D10 protects the
laser diode from reverse currents, S9 could short the output pins and the bypass diode D9
protects the driver in case of a load failure. To protect the laser diode during start-up of the
driver, S0 remains opened until the supply voltage has reached a stable level. In case of a
failure, the control unit disables the driver. A soft start mechanism slowly rises the current
after an over temperature shutdown or at start-up.
Operation principle of the LDP-C/CW driver family