Name: PCX-7421 Laser Diode Driver
Brand: Berkeley Nucleonics

PCX-7421 CW/QCW Laser Diode Driver

An air-cooled, high-power current source for diode lasers, bars, and arrays. The PCX-7421 drives pulsed/QCW output from 50 mA to 21.5 A and CW output from 3.0 A to 5.8 A, with rise time under 25 ns and a 24 V compliance window. The internal source covers 40 Hz to 100 kHz, an external source extends it to 1 MHz, and the bias current can be pulsed and triggered independently from the main current.

PCX-7421 · Product Data Sheet · Preliminary · Specifications subject to verification against the published BNC datasheet

1Overview

The PCX-7421 is an air-cooled, high-powered CW/QCW current source designed to drive diode lasers, bars, and arrays. The pulsed output current is adjustable from 50 mA to 21.5 A, the pulse width is adjustable from 50 ns to 500 ms, and the rise time is under 25 ns. The pulse repetition rate is selectable from 40 Hz to 100 kHz with the internal source, and from single-shot to 1 MHz with an external source.

The instrument provides both QCW (pulsed) and CW (DC) outputs. It serves as a CW driver at currents from 3.0 A to 5.8 A, and as a pulsed/QCW driver at currents from 50 mA to 21.5 A. The output may be biased to any CW current from 0.050 A to 5.8 A, then pulsed above that bias up to 15.7 A maximum. A bias-pulsing feature allows the bias current to be pulsed and triggered independently from the main current.

Directed Energy, Inc. is now a division of Berkeley Nucleonics. The PCX-7421 is the same design, built in California, with one support path. Operation runs from intuitive front-panel controls, and the OLED display confirms bias and pulsed current setpoints, internal trigger pulse width and frequency, and any error or fault messages.

PCX-7421 laser output PCBA with PCM-7700 load board connectors — Laser Output PCBA. Connection to the diode is made through low-impedance twisted-pair cables that preserve the fidelity of high-speed, large-amplitude current pulses.

2How It Works

A laser diode driver is a current source. The compliance voltage, 24 V on the PCX-7421, is the maximum voltage available to maintain the programmed current through the diode and the interconnect. Holding the current flat through the pulse is what preserves optical pulse shape, so every specification is measured with a low-inductance twisted-pair interconnect to the load.

The PCX-7421 separates the operating point from the pulse. A CW bias holds the diode anywhere from 0.050 A to 5.8 A, and the main current pulses above that floor up to 15.7 A in biased operation, or up to the full 21.5 A as a standalone pulsed/QCW source. Because the bias channel can be pulsed and triggered independently, the diode can be pre-conditioned and the main pulse fired with separate timing, which is useful for QCW thermal management and for shaping the leading edge of optical output.

CW, QCW, and pulsed. Run continuous current from 3.0 A to 5.8 A for CW operation, or pulse from 50 mA to 21.5 A for QCW and pulsed work. QCW lets a diode bar deliver high peak power while keeping average power, and junction temperature, within limits.

3Pulse & Bias Amplitude

All specifications are measured with a low-inductance twisted-pair interconnect cable to a load. The PCX-7421 meets or exceeds these specifications.

Pulse amplitude	Specification
Main current output range	3.0 A to 15.7 A (biased); 50 mA to 21.5 A (pulsed/QCW); 3.0 A to 5.8 A (CW)
Setpoint resolution	1 mA
Compliance voltage¹	24 V
Rise time	Less than 25 ns
Polarity	Positive
Maximum output power	Up to 250 W at 100% duty cycle

Bias amplitude	Specification
Bias current output range	50 mA to 5.8 A
Setpoint bias resolution	1 mA

Note 1. Laser diode drivers are current sources. The compliance voltage is the maximum voltage available to maintain the programmed current.

4Trigger Specifications

Internal trigger	Specification
Frequency range	40 Hz to 100 kHz
Frequency resolution	1 Hz (40 Hz to 300 Hz); 100 Hz (300 Hz to 5,000 Hz); 1000 Hz (5 kHz to 100 kHz)
Pulse width range	100 ns to 500 ms
Pulse width resolution	6400 ns (40 Hz to 300 Hz); 1600 ns (300 Hz to 5,000 Hz); 100 ns (5 kHz to 100 kHz)
Rise time	Less than 25 ns
Polarity	Positive

External trigger	Specification
Frequency range	1 MHz or less
Minimum pulse width	50 ns
Maximum pulse width	100% duty cycle, up to 250 W
Termination	50 ohm or 10,000 ohm
Connector	BNC
Input voltage levels	0 V to 5.0 V; high = output to load, low = no output to load

Trigger sync output	Specification
Termination	50 ohm
Connector	BNC
Output voltage levels	0 V to 2.7 V

5General Specifications

Parameter	Specification
Power requirements	47 Hz to 63 Hz; 100 VAC to 120 VAC plus or minus 10%, or 220 VAC to 240 VAC plus or minus 10%
AC connector type	NEMA C-14
Size (H × W × D)	8.9 cm × 28.5 cm × 53.4 cm; standard with rack-mount ears (33.6 cm wide at ears); requires 2U spacer
Weight	8.4 kg
Operating temperature	15 C to 40 C
Cooling	Air cooled, flow front to rear of unit
User interface	OLED display with front-panel controls

6Output Protection & Safety

The PCX-7421 uses advanced circuitry to protect both the diode and the driver. At turn-on, and at any time the output is not enabled, the output is electronically shorted to ground so that no current flows through the diode. This short-on-disable behavior is the primary defense against accidental diode damage during connection and setup.

A front-panel interlock key gates the output. When the key is off, the output is disabled. To enable the output, the key must be on and the system enable must be made, either manually or through the computer interface. A remote interlock is also provided, so the driver can be tied into a larger safety chain.

Stay within compliance and use the supplied cable. Keep the combined diode forward voltage and interconnect drop inside the 24 V compliance window. Always drive the load through the supplied low-impedance twisted-pair cables so the specified rise time and pulse fidelity hold.

7Control & Interfaces

The PCX-7421 is operated through intuitive front-panel controls, with an OLED display that gives immediate visual confirmation of every operating parameter, including bias and pulsed current setpoints, internal trigger pulse width and frequency, and error or fault messages.

For automated applications, complete control of the driver is provided through RS-232 and USB computer interfaces. Up to five system configurations can be stored in internal non-volatile memory, providing instant recall of frequently used setups. USB driver support covers Windows 7 through 10, Windows XP, Linux, and Mac OS X.

8Applications

The PCX-7421 fits applications that need high pulsed current with independent bias control, across CW, QCW, and pulsed modes.

Diode lasers, bars, and arrays. Drive high-power single emitters, bars, and arrays with rise time under 25 ns and current up to 21.5 A.
QCW pump sources. Pump solid-state and fiber lasers in quasi-CW mode, holding peak optical power high while keeping average power and junction temperature in range.
LiDAR and rangefinding. Generate fast, large-amplitude current pulses for time-of-flight and ranging systems.
Materials processing and research. Supply continuous or pulsed current for marking, micromachining, and laboratory diode characterization.

9Ordering Information

Part number	Description
PCX-7421	Precision Pulsed Current Source
6100-0119	Output Cable (twisted pair), requires 2
6045-0134	Laser Output PCBA
PCA-9410	BNC Shorting Connector

Each PCX-7421 is delivered with two output twisted-pair cables, one laser output PCBA, and a BNC shorting connector.

Contact

For a quote, configuration help, or application support, reach the Berkeley Nucleonics team.

Email: info@berkeleynucleonics.com
Phone: 800-234-7858

Request the full datasheet. This page summarizes the PCX-7421 specifications. For the complete published datasheet and a configuration tailored to your laser, contact Berkeley Nucleonics.