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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 1
A fast LED driver prototype for HCAL calibration
HCAL meeting DESY HH
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 2
Proposal for calibration system
• New LED driver with reduced crosstalk• A tunable calibration light in the range 0 to
100MIP• Simplification of the optical system: one
LED -> one side emitting fibre, one row of scintillator tiles
• PIN photo diode, do we need them?
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 3
LED driver strategy for SiPM calibration
• At AHCAL prototype (uses SiPM), we used CMB, calibration system with UV-LED 400nm driven by very fast rectangular pulses (1ns rise/fall time).
• Steep Rectangular waveform satisfied the needs to vary pulse-width, BUT creates lots of harmonics electromagnetic crosstalk!
• We have found fixed pulse-width to about 6ns, we can go to use narrow band ->smooth waveform ≈ less RF interference = Quasi Resonant LED driver (single pulse)
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 4
Quasi-Resonant LED driverLC circuit, heavily dumped
• 2CH board• primary tested• With printed indictor
2ns pulse-width
• Prototyping• Used my lovely single
side copper foil PCB• We need more work on
components • optimization
•Simulation pulse-width 5ns with 33nH inductance
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 5
QR LED driver Simulationoscilloscope oscilloscope
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 6
Simulation at 1.5V amplitude
• XSC1: • Upper trace - sync pulse• Lower trace – voltage at LED
hot end
• XSC2: Lower trace LED current
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 7
Simulation at 3V
• XSC1: • Upper trace - sync pulse• Lower trace – voltage at LED
hot end
• XSC2: Lower trace LED current
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 8
Prototype of QR LED driver
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 9
Tests shows more power on LED
• We see response of PIN photodiode at oscilloscope
• Amplitude up to 2mVpeak @ 50 Ω
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 10
Response to low amplitude
• LED current (cyan)
(voltage @ 10Ohm)
• PIN response (yellow)
• LED anode (violet)
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 11
Response to middle amplitude
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 12
Response to high amplitude• 200mA
current at LED
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 13
Response to high amplitude• The Light
from LED was optically blocked to PIN.
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 14
2CH prototype
Double sided PCB
2 QRLED driver
2PIN photodiode preamp
Rate generator 1Hz to 10kHz
Voltage regulators
Amplitude control
V-calib and T-calib interface
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 15
2CH QRLED board
There is a detail of two QRLED driver
Printed inductors with taps, left is connected by tin joint
Two trimmers equivalise delays between CH A and B
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 16
Principal schema of QRLed driver
AA
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 17
LED Current
View of the LED pulse for a small amplitude (0.6 A)
Measured with 1GHz voltage differential probe and 1GHz scope TDS4104 at 1Ω smd resistor
4ns/div 0.5A/div
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 18
LED current• View of the LED
pulse for a middle amplitude (1.0 A)
• Measured with 1GHz voltage differential probe and 1GHz scope TDS4104 at 1Ω smd resistor
• 4ns/div 0.5A/div
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 19
LED current• View of the
LED current pulse for the highest amplitude (2.3 A)
• Measured with 1GHz
voltage differential probe and 1GHz scope TDS4104 at 1Ω smd resistor
• 4ns/div 0.5A/div
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HCAL HH, DEC19, 2007
Ivo Polak, IoP Prague 20
Conclusion• QR LED driver is very promising technique to
reduce Electro-Magnetic-Interferences• PCB of the two-channel QR LED driver is ready
to further test• January - more test with Photodetectors• February – more assembled PCBs available• May – designing of multichannel system with
light transfer in side-emitting fibres, mechanical integration to a new detector design