AD8305 Analog Devices, AD8305 Datasheet - Page 15

• Manufacturer Part Number: AD8305
• Description: 100 Db-range (10nA-1mA) Logarithmic Converter
• Manufacturer: Analog Devices

REV. A
Component
P1
P2, R8, R9, R10,
R11, R17, R18
R2, R3, R4, R6, R14, Buffer Amplifier/Output Interface. The logarithmic slope of the AD8305
C2, C7, C9, C10
R1, R7, R19, R20
R12, R15, C3,
C4, C5, C6
C11
R13, R16, C1, C8
IREF, INPT, PD,
LK1, R5
J1
Function
Supply Interface. Provides access to supply pins, VNEG, COMM, and VPOS. P1 = Installed
Monitor Interface. By adding 0 W resistors to R8, R9, R10, R11, R17, and R18, P2 = Not Installed
the VRDZ, VREF, VSUM, VOUT, and VLOG pin voltages can be monitored
using a high impedance probe.
can be altered using the buffer’s gain-setting resistors, R2 and R3. R4, R14,
and C2 allow variation in the buffer loading. R6, C7, C9, and C10 are
provided for a variety of filtering applications.
Intercept Adjustment. The voltage dropped across resistor R1 determines the R1 = 200 kW (Size 0603)
intercept reference current, nominally set to 10 mA using a 200 kW 1% resistor.
R7 and R19 can be used to adjust the output-offset voltage at the VLOG output. R20 = Open (Size 0603)
Supply Decoupling.
VSUM Decoupling Capacitor.
Input Compensation. Provides essential HF compensation at the input pins,
INPT and IREF.
Input Interface. The test board is configured to accept a current through the
SMA connector labeled INPT. An SC-style packaged photodiode can be
used in place of the INPT SMA for optical interfacing. By removing R1 and
adding a 0 W short for R5, a second current can be applied to the IREF input R5 = Open (Size 0603)
(also SMA) for evaluating the AD8305 in log-ratio applications.
SC-Style Photodiode. Allows for direct mounting of SC style photodiodes.
Table I. Evaluation Board Configuration Options
–15–
Default Condition
R8 = R9 = R10 = Open (Size 0603)
R17 = R18 = Open (Size 0603)
R2 = R6 = 0 W (Size 0603)
R3 = R4 = Open (Size 0603)
R11 = R14 = 0 W (Size 0603)
C2 = C7 = Open (Size 0603)
C9 = C10 = Open (Size 0603)
VLOG = VOUT = Installed
R7 = R19 = 0 W (Size 0603)
C3 = C4 = 0.01 F
(Size 0603)
C5 = C6 = 0.1 F (Size 0603)
R12 = R15 = 0 W (Size 0603)
C11 = 1 nF (Size 0603)
R13 = R16 = 1 kW (Size 0603)
C1 = C8 = 1 nF (Size 0603)
IREF = INPT = Installed
PD = Not Installed
LK1 = Installed
J1 = Not Installed
AD8305