NIM Model 621 BLP Quad Programmable Discriminator

Designed in response to a growing interest in complete computer control of high energy physics experiments, the new LRS Model 621BLP Quad 100 MHz Discriminator not only offers all of the features of the widely-used Model 621 AL, but it also permits the threshold and width of each channel to be remotely set by an externallyapplied DC voltage signal. When the proper control voltage is applied to the rear-panel 20-pin connector, the effect of the front-panel threshold or width pot is negated and remote control presides. Among other applications, such remote programming ability permits on-line threshold corrections to account for drifts in photomultiplier high voltage and resultant gain changes.

The threshold of the 621BLP is variable from -30 mV to -1 volt via front-panel screwdriver adjustment. This low minimum threshold permits experimenters to routinely reverse-terminate photomultiplier anodes and, coupled with the extremely low input reflections, greatly reduces the possibility of multiple-pulsing due to input reflections in the system.

Each channel of the 621 BLP provides 6 (five negative and one complementary) fast NIM-level current source outputs. The flexibility resulting from this high output fan-out capability permits simple and more efficient logic design. Output mode is determined by a front-panel locking toggle switch. In the Update Only mode the output durations are adjustable from 5 ns to 1 /is and are independent of input amplitude, duration, and rate. Their long-term stability is excellent, permitting their direct use in critical coincidence applications without any need for external clipping cables. In the Burst Guard mode the output duration is either equal to the time-overthreshold of the input signal or is equal to the preset output duration, whichever is greater. To achieve this, a timeover-threshold signal from the discriminator front end is logically OR-ed with the output of the pulse-former stage. Input burst rates that exceed the DPR of the unit will cause an output for the duration of the burst. (Normally, a single standardized output would appear, but the remainder of the burst would not be seen).

The pulse-forming stage of the 621 BLP is deadtimeless (updating), and the units may be retriggered during the time an output from a previous input signal is being produced.

SPECIFICATIONS
NIM Model 621BLP QUAD PROGRAMMABLE DISCRIMINATOR

INPUT CHARACTERISTICS

Signal Input:

Threshold, 30 mV to 1.0 volt; front-panel screwdriver adjustment (screwdriver in- cluded); 50 Ohm protected to +/- 5A for 0.5 usec, clamping at +1 and -7volts; reflections 4% t pulses of 2 ns risetime; stability 0.2%/Deg.C over 20Deg.C to 60'C operating range; = +/- 1 mV; threshold monitor has 10:1 ratio of monitor voltage to actual voltage, +/- 2%.

Bin Gate:

Slow gate via rear connector and rear-panel ON-OFF switch; risetimes and falltimes, approximately 50 ns; clamp to ground from 5 V inhibits; direct-coupled.

OUTPUT CHARACTERISTICS

Bridged Negative Outputs:

2 pair; NIM; quiescently 0 mA, 32 mA during output; risetimes and falltimes (all outputs terminated in 50 Ohm) typically 2.0 ns (max. 2.5 ns), 10% to 90%. Output falltimes slightly longer on wide output durations. Width stability better than +/- 0.2%/'C maximum.

Fast Negative Timing Output:

One; NIM; quiescently 0 mA, 16 mA during output. other characteristics same as above, except risetimes and falltimes are typically <= 1.5 ns (max. 2.0 ns), and minimum width is -- 6 ns.

Complementary Output:

One; quiescently 16 mA, 0 mA during output. Other characteristics same as for Fast Negative Timing Output.

Duration:

Update Only Mode: 5 ns to 1 As, continuously variable up to 600 ns via front-panel screwdriver control (narrower widths possible at slight expense of amplitude). Burst Guard Mode: Output duration is either equal to the time-overthreshold of the input signal or equal to the preset duration. whichever is greater. For input burst rates greater than the DPR of the unit, the output is equal to the duration of the burst.

GENERAL

Maximum Rate

110 MHz typical, input and output.

Double-Pulse Resolution:

Less than 9 ns at minimum output width setting.

Time Slewing:

1 ns for input amplitudes 11ODeg./% of threshold and above.

Input-Output Delay:

9.5 ns typical.

Multiple-Pulsing:

None; one and only one output pulse of preset duration is produced for each input pulse regardless of input pulse amplitude or duration.

Packaging:

In RF shielded AEC/NIM #1 module (AEC Report #TID-20893); Lemo-type connectors.

Power Requirements:

-6 V at 450 mA;
+ 6 V at 150 mA;
-12 Vat 165 mA;
+12 V at20 mA;
24 V at 85mA.

High Impedance Option:

The Model 621 BLP is also available with a bridged high-impedance input (at the expense Of one negative output) at additional cost.

REMOTE PROGRAMMING CHARACTERISTICS

Threshold Control:

Actual threshold (VT at rear panel pin)/10, where 300 mV -- \Vt -10 volts. Input impedance = 1 KOhm (front-panel threshold control should be set to 500 mV. Input impedance approaches 200 Ohm at 1 volt threshold.)

Width Control:

Control range is quasi-logarithmic, 0 volts corresponding to minimum width, +6 volts corresponding to maximum width. Input impedance = 1 KOHm.

Pin Connections:

Pin

Function

Pin

Function

A

Ch. 1 VT

H

Ch. 3 VT

B

GROUND

J

GROUND

C

Ch. 1 Vw

K

Ch. 3 Vw

D

Ch. 2 VT

L

Ch. 4 VT

E

GROUND

M

GROUND

F

Ch. 2 Vw

N

Ch. 4 Vw

Rear-Connector Type:

LRS Model CK-20M Connector Kit or AMP #201356-1, male pins.

Mating Connector Type:

LRS Model CK-20 Connector Kit or AMP #200346-2, female sockets.

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INPUT CHARACTERISTICS
Signal Input:	Threshold, 30 mV to 1.0 volt; front-panel screwdriver adjustment (screwdriver in- cluded); 50 Ohm protected to +/- 5A for 0.5 usec, clamping at +1 and -7volts; reflections 4% t pulses of 2 ns risetime; stability 0.2%/Deg.C over 20Deg.C to 60'C operating range; = +/- 1 mV; threshold monitor has 10:1 ratio of monitor voltage to actual voltage, +/- 2%.
Bin Gate:	Slow gate via rear connector and rear-panel ON-OFF switch; risetimes and falltimes, approximately 50 ns; clamp to ground from 5 V inhibits; direct-coupled.
OUTPUT CHARACTERISTICS
Bridged Negative Outputs:	2 pair; NIM; quiescently 0 mA, 32 mA during output; risetimes and falltimes (all outputs terminated in 50 Ohm) typically 2.0 ns (max. 2.5 ns), 10% to 90%. Output falltimes slightly longer on wide output durations. Width stability better than +/- 0.2%/'C maximum.
Fast Negative Timing Output:	One; NIM; quiescently 0 mA, 16 mA during output. other characteristics same as above, except risetimes and falltimes are typically <= 1.5 ns (max. 2.0 ns), and minimum width is -- 6 ns.
Complementary Output:	One; quiescently 16 mA, 0 mA during output. Other characteristics same as for Fast Negative Timing Output.
Duration:	Update Only Mode: 5 ns to 1 As, continuously variable up to 600 ns via front-panel screwdriver control (narrower widths possible at slight expense of amplitude). Burst Guard Mode: Output duration is either equal to the time-overthreshold of the input signal or equal to the preset duration. whichever is greater. For input burst rates greater than the DPR of the unit, the output is equal to the duration of the burst.
GENERAL
Maximum Rate	110 MHz typical, input and output.
Double-Pulse Resolution:	Less than 9 ns at minimum output width setting.
Time Slewing:	1 ns for input amplitudes 11ODeg./% of threshold and above.
Input-Output Delay:	9.5 ns typical.
Multiple-Pulsing:	None; one and only one output pulse of preset duration is produced for each input pulse regardless of input pulse amplitude or duration.
Packaging:	In RF shielded AEC/NIM #1 module (AEC Report #TID-20893); Lemo-type connectors.
Power Requirements:	-6 V at 450 mA; + 6 V at 150 mA; -12 Vat 165 mA; +12 V at20 mA; 24 V at 85mA.
High Impedance Option:	The Model 621 BLP is also available with a bridged high-impedance input (at the expense Of one negative output) at additional cost.
REMOTE PROGRAMMING CHARACTERISTICS
Threshold Control:	Actual threshold (VT at rear panel pin)/10, where 300 mV -- \Vt -10 volts. Input impedance = 1 KOhm (front-panel threshold control should be set to 500 mV. Input impedance approaches 200 Ohm at 1 volt threshold.)
Width Control:	Control range is quasi-logarithmic, 0 volts corresponding to minimum width, +6 volts corresponding to maximum width. Input impedance = 1 KOHm.

Pin Connections:	Pin	Function	Pin	Function
	A	Ch. 1 VT	H	Ch. 3 VT
	B	GROUND	J	GROUND
	C	Ch. 1 Vw	K	Ch. 3 Vw
	D	Ch. 2 VT	L	Ch. 4 VT
	E	GROUND	M	GROUND
	F	Ch. 2 Vw	N	Ch. 4 Vw

Rear-Connector Type:	LRS Model CK-20M Connector Kit or AMP #201356-1, male pins.
Mating Connector Type:	LRS Model CK-20 Connector Kit or AMP #200346-2, female sockets.