OVERVIEW
The LeCroy Model 4415A is a 16-input, non-updating discrimi- nator in a single-width CAMAC module. This type of discrimi- nator offers advantages in high input rate counting and timing applications since the counting rate (the rate of output pulse leading edges) is monotonic with input rate. The unit also of- fers differential ECL outputs which are compatible with LeCroy ECLine Series of data handler and trigger processor modules. For added flexibility, the 4415A accepts single-ended or differ- ential signal inputs and permits DC or AC coupling. Figure 1 shows the layout of the front panel.
The Model 4415A has 16 discriminator channels which operate at a maximum repetition rate of typically 9 MHz. The repeti- tion rate can be increased to approximately 30 MHz or de- creased below 9 MHz by a simple user modification to the tim- ing capacitors. The discriminator threshold is adjustable be- tween +/-30 mV and +/-600 mV, and is common to all channels. A common Veto input signal will disable the unit for the dura- tion of this input. Also, a test input or CAMAC command per- mits firing all channels simultaneously for system evaluation. A CAMAC programmable mask may be applied to select only a subset of channels which will fire during this test.
A threshold set by the front-panel potentiometer can be read by a voltmeter at a front-panel test point. This same test point can be used to program the threshold with an external input voltage. In either case, for readout or for external programming of the threshold, the test point is a factor of 10 larger than the actual applied threshold voltage.
High density and low price per channel are made possible through the use of the LeCroy HVL100 hybrid integrated cir- cuit. Sixteen of these hybrids, one per channel, are used in the 4415A and provide all the essential function of the discriminator.
SPECIFICATIONS
Input Characteristics
Signal Inputs: 16 inputs via a front-panel 34-pin connector
single-ended or differential, DC-coupled (AC-coupled op-
tional). Common mode voltage range +/-3 V. Impedance, 110
Ohm +/-5% differential; 55 Ohm +/-5% from each pin to ground.
Threshold: Set via a screwdriver adjustable front-panel, potenti-
ometer or via an external voltage applied to the threshold con-
trol connector. The threshold is common to all channels.
Threshold Control: Front-panel 2-pin connector; high imped-
ance, (5.6 kOhm). Used as output, it indicates the internal thresh-
old control voltage. Used as input, it controls the threshold.
Threshold Control Ratio: Threshold monitor point on front
panel has 10:1 ratio of monitor voltage to actual voltage.
Range, -0.3 V to -6 V, corresponding to thresholds of 30 mV
to +600 mV for single-ended pulse, and 15 mV to 300 mV for
differential inputs due to AC coupling.
Threshold Range: -30 mV to -600 mV (+/-10 mV or +/-10%,
whichever is greater) for single-ended negative going pulses.
For positive going signals with a risetime less than 300 usec, the
threshold is +30 mV to +600 mV. For differential signals the
range is 15 mV to 300 mV (see Figure 2).
Threshold Uncertainty: The threshold will drift with both tem-
perature and supply voltage. The temperature coefficient for
the drift is 50 uV/'C and the threshold coefficient for 6 V
power supply drift is 10 mV/V.
Hysteresis: 3.6 mV typical.
Input-Output Delay: 22 nsec, typical (2X threshold, see Time
Slewing below).
Test Input: One Lemo front-panel connector, 50 Ohm +/-2% im-
pedance, triggers all channels simultaneously. Requires NIM
level signal (-16 mA into 50 Ohm = -0.8 V. Tolerance is +/-4 mA
according to NIM standard). Minimum width: 10 nsec, direct
coupled.
Veto Input: One Lemo front-panel connector 50 Ohm +/-2% input
impedance, inhibits all outputs during input of VETO. NIM
level signal (-16 mA into 50 Ohm = -0.8 V. Tolerance is +/-4 mA
according to NIM Standard); direct coupled.
Output Characteristics
Signal Output: 2 X 16, two outputs per channel in two front-
panel 34-pin connectors; ECL differential level (-0.8, -1.6 V)
into 100 Ohm twisted pair. Duration: 100 nsec to 1 usec (factory
set; user modification for other values. See Chapter 6). Output
duration set by front-panel screwdriver control, common to all
channels. Risetimes and fall times typical 2.2 nsec. Width sta-
bility: <0.2%'C.
Timing Characteristics:
Double Pulse Resolution: Typical 1 10% of output width (lead-
ing edge to leading edge) or width of pulse plus 12 nsec which-
ever is greater.
Time Slewing: <2 nsec for input amplitudes from 2 to 20 times
threshold.
Tracking Error: The tracking error is given by the ability of
the input stage of the 4415A to follow the input signal leading
edge. Tests on the 4415A indicate that the tracking error is not
in excess of 1 nsec.
Crosstalk: Crosstalk between adjacent channels is isolated by
-60 dB for input pulses with risetimes exceeding 2 nsec.
Test to Output Delay: Typical 40 nsec.
Veto to Output Delay: Typical 10 nsec.
Multiple Pulsing: None; one and only one output pulse is pro-
duced regardless of input pulse amplitude and duration.
Power Requirement: 1.3 A at +6 V
4.25 A at -6 V
20 mA at -24 V
33.8 W Total
CONTROLS AND
CONNECTORS
Signal Input
Signal input to all 16 channels of the 4415A is made via a com-
mon 34-pin front-panel connector. These signals may be either
single-ended or differential such as differential ECL levels. The
unit permits DC or AC coupling of the signals.
For single-ended inputs, if the negative input pin is grounded
and positive pulses are sent, the 4415A is AC coupled. A DC
level shift will occur on pin 13 of the HVL 100 Hybrid as a
function of the duty cycle of the input, which is common in AC
coupled circuits. This variation will result in an effective thresh-
old level shift with a time constant of 300 usec. Conversely, if
the positive pin is grounded and negative pulses are input, then
the discriminator is DC coupled and experiences no threshold
level shift.
If both positive and negative going complementary pulses are
applied to the input pins, the positive side is AC coupled and
the negative side DC coupled. Again, the threshold would vary
with input duty cycle as above.
The input signals may be AC coupled at the inputs by cutting
the jumpers which bypass capacitors on both positive and nega-
tive input pins (see Chapter 6). This AC coupling ability is use-
ful when, for example, differential ECL signals are input. ECL
signal levels are -0.8 V and -1.6 V, so AC coupling is required.
When this modification is performed, the time constant for
threshold drift is lowered to about 12 usec.
Threshold
The threshold range of the 4415A discriminator is -30 mV to
-600 mV for negative going single-ended pulses. For positive
going single-ended pulses with a risetime less than 300 usec, the
range is +30 mV to +600 mV. For differential pulses the range
is 15 mV to 300 mV. The threshold value is common to all
channels, and is set either by a front-panel, 15-turn potenti-
ometer, or by an external voltage applied to the front-panel test
point.
A front-panel two-pin connector provides a voltage output that
is ten times that applied to the input signal. Since the voltage
present at this connector is then sent to the portion of the cir-
cuit that actually provides the threshold for the HVL100 hy-
brids, any external voltage applied here will result in a factor of
10 less threshold voltage applied to the HVL100. Therefore,
this connector can be used either as a front-panel test point
indicating the threshold setting or as a threshold programming
input.
Veto Input
A front-panel Lemo connector accepts NIM level signals to
VETO or inhibit all 16 outputs simultaneously during a logical 1
state (<=-600 mV).
If a complementary NIM Level (NIM) is input to the VETO
connector, then the unit will act as a gated coincidence unit be-
tween the individual inputs and the VETO input. In other
words, the discriminators will generate an output only when the
input level exceeds the set threshold and while these signals oc-
cur during a logical 0 (>=-100 mV) state of the complementary
input to the VETO.
Note that an output pulse can occur if the input initiates an out
put which extends beyond the end of the VETO input. The
resulting discriminator output width will equal the set width mi-
nus the portion of the pulse which overlaps the VETO signal.
TEST Input
The TEST input is a front-panel Lemo connector which triggers
all channels simultaneously with the receipt of a NIM signal.
However, initiation of the TEST mode requires the REMOTE/
LOCAL switch to be in the REMOTE position. A front-panel
LED indicates when TEST is in operation.
Output
The output of the 4415A is differential ECL pulse pairs suitable
for driving twisted pair cables. Two outputs per channel are
provided from two 34-pin front-panel connectors. These cables
may be ordered from LeCroy as Model DC2/34.
The output of selected channels in the TEST mode can be dis-
abled or masked by loading a 16-bit word via CAMAC F(16)
command into a storage register.
Width Adjustment
The output width is continuously adjustable by a 15-turn front-
panel potentiometer. The width range is from less than 100
nsec to over 1 usec as supplied from the factory and is common
to all channels. To alter the range of the width adjustment, a
simple user modification can be made.
REMOTE/LOCAL
The front-panel switch allows all channels to be tested when in
the REMOTE position. In the LOCAL position, the TEST
mode and mask register are disabled.
CAMAC Commands
F(16)-A(O): Writes mask register on CAMAC write line W1 -
W16. Q response generated.
F(17)-A(O): Writes a bit, on CAMAC Write line W1 to Enable/
Disable Test Mode. To enable Test mode, W1=1. To disable,
W1=0. Q response is generated.
F(25)-A(O): Triggers test function. A Q response is generated
in Test Mode when Remote/Local switch is in Remote mode
only.
F(27)-A(O): Remote/Local switch test. Q=l response if switch
is in Remote, Q=0 otherwise.
Z: Disables mask register and clears test mode.
I: Disables all outputs if in remote mode (User modification dis-
ables I, see Chapter 6 for details).
CAMAC Responses
X: An X response is generated for every valid F,N,A.
Q: A Q response is generated if the valid command can be exe-
cuted.