adl5317 Analog Devices, Inc., adl5317 Datasheet - Page 12

• Manufacturer Part Number: adl5317
• Description: Avalanche Photodiode Bias Controller And Wide Range 5 Na To 5 Ma Current Monitor
• Manufacturer: Analog Devices, Inc.

ADL5317
Measured rms noise voltage at the output of the
input current is shown in Figure 24 for the
and in cascade with the ADL5317. The relatively low noise
produced by the ADL5317, combined with the additional noise
filtering inherent in the frequency response characteristics of
the AD8305, result in minimal degradation to the noise
performance of the AD8305.
CHARACTERIZATION METHODS
During characterization, the ADL5317 was treated as a high
voltage 5:1 precision current mirror. To make accurate
measurements throughout the entire current range, calibrated
Keithley 236 current sources were used to create and measure
the test currents. Measurements at low current and high voltage
are very susceptible to leakage to the ground plane.
5.5m
5.0m
4.5m
4.0m
3.5m
3.0m
2.5m
2.0m
1.5m
1.0m
0.5m
Figure 24. Measured RMS Noise of AD8305 vs. AD8305
V
P_LOW
0
10n
AD8305 ONLY
0.1μF
10kΩ
100n
Cascaded with ADL5317
0Ω
V
SET
AD8305 AND
0.01μF
ADL5317
0.01μF
0.1μF
V
1μ
P_HIGH
Figure 23. Interfacing the ADL5317 to the AD8305 for High Accuracy APD Power Monitoring
1
2
3
4
0Ω
(A)
FALT
VSET
VPLV
VPHV
10μ
ADL5317
AD8305
100μ
AD8305
I
APD
by itself
GARD
IPDM
APD 1nF
1m
NC
NC
1kΩ
vs.
TIA
COMPENSATION
AD8305 INPUT
12
11
10
9
Rev. 0 | Page 12 of 16
NETWORK
1kΩ
DATA
PATH
0.01μF
1nF
4.7nF 2kΩ
200kΩ
10nA TO
To minimize leakage on the characterization board, the guard
pins are connected to traces that buffer VAPD and IPDM from
ground. The triax guard connector is also connected to the
GARD pin of the device to provide buffering along the cabling.
Figure 25 shows the primary characterization setup. The data
gathered is used directly, or with calculation, for all the static
measurements, including mirror error between IAPD and
IPDM , supply tracking offset, incremental gain, and VAPD vs.
IAPD. Component selection is very similar to that of the
evaluation board, except that triax connectors are used in place
of the SMA connectors. To measure the pulse response, output
noise, and bandwidth measurements, more specialized test
setups are used.
2.5V
I
1mA
PDM
FALT
CHARACTERIZATION BOARD
1
2
3
4
0.1μF
VPHV
VRDZ
VREF
IREF
INPT
DC SUPPLIES/DMM
ADL5317
Figure 25. Primary Characterization Setup
VPLV
AD8305
VSET
3V TO 12V
VCLH
VOUT
VLOG
SCAL
BFIN
VAPD
IPDM
12
11
10
9
TRIAX CONNECTORS:
SIGNAL - VAPD AND IPDM PINS
GUARD - GUARD PIN
SHIELD - GROUND
OUTPUT
V
LOG
OUT
KEITHLEY 236
KEITHLEY 236
10
= 0.2 ×
(I
PDM
/1nA)