ADL5315ACPZ-WP AD [Analog Devices], ADL5315ACPZ-WP Datasheet - Page 11

• Manufacturer Part Number: ADL5315ACPZ-WP
• Description: Precision Wide Range (3 nA to 3 mA) High-Side Current Mirror
• Manufacturer: AD [Analog Devices]

APPLICATIONS
The ADL5315 is primarily designed for wide dynamic range
applications, simplifying power monitoring designs where
access is only permitted to the cathode of a PIN photodiode or
receiver module. Figure 22 shows a typical application where
the ADL5315 is used to provide an accurate bias to a PIN diode
while simultaneously mirroring the diode current to be
measured by a translinear logarithmic amplifier.
In this application, the ADL5315 sets the bias voltage on the
PIN diode. This voltage is delivered at the INPT pin and is
controlled by the voltage at the VSET pin. VSET is driven by
the on-board reference V
The input current, I
the IOUT pin. This interface is optimized for use with any of
ADI’s translinear logarithmic amplifiers (for example, the
AD8304
measurement of the optical power incident upon the PIN.
If a linear voltage output is preferred at IOUT, a single external
resistor to ground is all that is necessary to perform the
conversion.
or AD8305) to offer a precise, wide dynamic range
V
NODE VOLTAGES
INPT
SREF
V
SET
, is precisely mirrored at a ratio of 1:1 to
= V
SREF
= V
PIN
POS
INPT
, which is equal to V
– 1V
TIA
4
3
2
1
COMM
SREF
VSET
INPT
20kΩ
REFERENCE
VOLTAGE
I
PD
DATA PATH
Figure 22. Typical Application Using the ADL5315
POS
− 1 V.
CURRENT
MIRROR
CURRENT
LIMITING
1:1
ADL5315
Rev. 0 | Page 11 of 20
I
PD
VPOS
RLIM
IOUT
NC
5
6
7
8
R
I
LIM =
LIM
AVERAGE POWER MONITORING
In applications where a modulated signal is incident upon the
photodiode, the average power of the signal can be measured.
Figure 21 shows the connections necessary for using the
ADL5315 in such a measurement system.
The value of the capacitor to ground should be selected to
eliminate errors due to modulation of the ADL5315 input
current.
= 48V
C
1mA – 16mA
PIN
VSUM
I
R
SET
LIM
INPT
LIM
– 3kΩ
Figure 21. Average Power Monitoring Using the ADL5315
TRANSLINEAR LOG AMP
TIA
4
3
2
1
THIS CONNECTION IS NOT NECESSARY,
BUT REDUCES ERRORS DUE TO LEAKAGE
CURRENTS AT LOW SIGNAL LEVELS.
AD8304, AD8305, ETC.
COMM
SREF
VSET
INPT
V
POS
20kΩ
REFERENCE
VOLTAGE
I
PD
DATA PATH
CURRENT
MIRROR
CURRENT
LIMITING
1:1
OPTICAL
POWER
ADL5315
I
PD
VPOS
RLIM
IOUT
NC
5
6
7
8
ADL5315
V
POS
LINEAR
VOLTAGE
OUTPUT