AD8304 데이터 시트보기 (PDF) - Analog Devices

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AD8304

160 dB Range (100 pA –10 mA) Logarithmic Converter

Analog Devices 

AD8304

Figure 23. Component Side Layout

Figure 24. Component Side Silkscreen

Component

VP, VN, AGND

SW1, R10

R1, R2

R3, R4

R5, R6, R7, R8, R9

C1, C2, C3, C4, C9

Table V. Evaluation Board Configuration Options

Function

Positive and Negative Supply and Ground Pins

Device Enable: When SW1 is in the “0” position, the PWDN Pin is

connected to ground and the AD8304 is in its normal operating mode.

Buffer Amplifier Gain/Slope Adjustment: The logarithmic slope

of the AD8304 can be altered using the buffer’s gain-setting resistors,

R1 and R2.

Intercept Adjustment: A dc offset can be applied to the input term-

inals of the buffer amplifier to adjust the effective logarithmic intercept.

Bias Adjustment: The voltage on the VSUM and INPT Pins can be

altered using appropriate resistor values. R9 is populated with a decoup-

ling capacitor to reduce noise pickup. The decoupling capacitor can be

removed when a fixed bias is applied to VSUM.

Supply Decoupling Capacitors

C10

Photodiode Biaser Decoupling: Provides high frequency decoupling

of the adaptive bias output at Pin VPDB.

C5, C6, C7, C8, R11, Output Filtering: Allows implementation of a variety of filter config-

R12, R13, R14

urations, from simple RC low-pass filters to three-pole Sallen and Key.

R15, C11

LK1, LK2

Input Filtering: Provides essential HF compensation at the input

Pin INPT.

Guard/Shield Options: The shells of the SMA connectors used

for the input and the photodiode bias can be set to the voltage on the

VSUM Pin or connected to ground.

Default Condition

Not Applicable

SW1 = Installed

R10 = 10 kΩ (Size 0603)

R1 = Open (Size 0603)

R2 = 0 Ω (Size 0603)

R3 = Open (Size 0603)

R4 = Open (Size 0603)

R5 = R6 = Open (Size 0603)

R7 = R8 = Open (Size 0603)

R9 = 0.1 µF (Size 0603)

C1 = C4 = 0.1 µF (Size 0603)

C2 = C3 = 1 nF (Size 0603)

C9 = 10 nF (Size 0603)

C10 = 0.1 µF (Size 0603)

R11 = R13 = 0 Ω (Size 0603)

R12 = Open (Size 0603)

R14 = 0 Ω (Size 0603)

C5 = C6 = Open (Size 0603)

C7 = C8 = Open (Size 0603)

R15 = 750 Ω (Size 0603)

C11 = 1 nF (Size 0603)

LK1 = Installed

LK2 = Open

REV. A

–19–

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