MAX3864 データシートの表示（PDF） - Maxim Integrated

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MAX3864

2.5Gbps, +3V to +5.5V, Wide Dynamic Range Transimpedance Preamplifier

Maxim Integrated 

2.5Gbps, +3V to +5.5V, Wide Dynamic Range

Transimpedance Preamplifier

TOP VIEW OF TO-46 HEADER

GND

OUT-

PHOTODIODE

CFILT

VCC

CVCC

OUT+

VCC

VCC

200Ω

IN

MAX3864

PHOTODIODE IS MOUNTED

ON CFILT.

CASE IS GROUND.

Figure 5. Suggested Layout for TO-46 Header

Photodiode Filter

Supply voltage noise at the photodiode cathode pro-

duces a current I = CPD ΔV / Δt, which reduces the

receiver sensitivity (CPD is the photodiode capaci-

tance). The filter resistor of the MAX3864, combined

with an external capacitor, can be used to reduce this

noise (see the Typical Application Circuit). Current gen-

erated by supply noise voltage is divided between

CFILTER and CPD. The input noise current due to sup-

ply noise is (assuming the filter capacitor is much larg-

er than the photodiode capacitance):

( )( ) VNOISE CPD

( )( ) INOISE =

RFILTER CFILTER

If the amount of tolerable noise is known, the filter

capacitor can be easily selected:

( )( ) VNOISE CPD

( )( ) CFILTER =

RFILTER INOISE

For example, with a maximum noise voltage equal to

100mVP-P, CPD = 0.85pF, RFILTER = 750Ω, and INOISE

selected to be 250nA (half of the MAX3864’s input noise):

( )( ) 100mV 0.85pF

( )( ) CFILTER =

= 453pF

750Ω 250nA

GND

Figure 6. Equivalent Input Circuit

Wire Bonding

For high current density and reliable operation, the

MAX3864 uses gold metalization. Connections to the

die should be made with gold wire only, using ball-

bonding. Wedge bonding is not recommended. Die

thickness is typically 15mils (0.375mm).

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