Datasheet

REV. A
AD8304
–19–
Table V. Evaluation Board Configuration Options
Component Function Default Condition
V
P
, V
N
, AGND Positive and Negative Supply and Ground Pins Not Applicable
SW1, R10 Device Enable: When SW1 is in the “0” position, the PWDN Pin is SW1 = Installed
connected to ground and the AD8304 is in its normal operating mode. R10 = 10 kΩ (Size 0603)
R1, R2 Buffer Amplifier Gain/Slope Adjustment: The logarithmic slope R1 = Open (Size 0603)
of the AD8304 can be altered using the buffer’s gain-setting resistors, R2 = 0 Ω (Size 0603)
R1 and R2.
R3, R4 Intercept Adjustment: A dc offset can be applied to the input term- R3 = Open (Size 0603)
inals of the buffer amplifier to adjust the effective logarithmic intercept. R4 = Open (Size 0603)
R5, R6, R7, R8, R9 Bias Adjustment: The voltage on the VSUM and INPT Pins can be R5 = R6 = Open (Size 0603)
altered using appropriate resistor values. R9 is populated with a decoup- R7 = R8 = Open (Size 0603)
ling capacitor to reduce noise pickup. The decoupling capacitor can be R9 = 0.1 µF (Size 0603)
removed when a fixed bias is applied to VSUM.
C1, C2, C3, C4, C9 Supply Decoupling Capacitors C1 = C4 = 0.1 µF (Size 0603)
C2 = C3 = 1 nF (Size 0603)
C9 = 10 nF (Size 0603)
C10 Photodiode Biaser Decoupling: Provides high frequency decoupling C10 = 0.1 µF (Size 0603)
of the adaptive bias output at Pin VPDB.
C5, C6, C7, C8, R11, Output Filtering: Allows implementation of a variety of filter config- R11 = R13 = 0 Ω (Size 0603)
R12, R13, R14 urations, from simple RC low-pass filters to three-pole Sallen and Key. R12 = Open (Size 0603)
C7 = C8 = Open (Size 0603)
R15, C11 Input Filtering: Provides essential HF compensation at the input R15 = 750 Ω (Size 0603)
Pin INPT. C11 = 1 nF (Size 0603)
LK1, LK2 Guard/Shield Options: The shells of the SMA connectors used LK1 = Installed
for the input and the photodiode bias can be set to the voltage on the LK2 = Open
VSUM Pin or connected to ground.
Figure 23. Component Side Layout Figure 24. Component Side Silkscreen
R14 = 0 Ω (Size 0603)
C5 = C6 = Open (Size 0603)