MAX3266EVKIT-SO 데이터 시트보기 (PDF) - Maxim Integrated

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MAX3266EVKIT-SO

MAX3266/MAX3267 Evaluation Kits

Maxim Integrated 

MAX3266/MAX3267 Evaluation Kits

To allow characterization without a photodiode, the

MAX3266 EV kit provides a simple circuit that emulates

a photodiode using common voltage output signal

sources.

The connector at INPUT is terminated with 50Ω to

ground. This voltage is then AC coupled to a resistance

in series with the MAX3266’s input, creating an input

current. U2 and U3 form a simple DC current source

that is used to apply a DC current to the input signal.

The values of the series resistive elements, R1 and R2,

have been carefully selected not to change the band-

width of the transimpedance amplifier. Surface-mount

resistors have parasitic capacitance that reduces their

impedance at frequencies above 1GHz. The user

should carefully evaluate any changes to R1 and R2

using the calibration network provided on the EV kit.

Table 1 shows the recommended resistor values.

Photodiode Emulation

The following procedure can be used to emulate the

high-speed current signal generated by a photodiode:

1) Select the desired optical power (PAVG in dBm)

and extinction ratio (re).

2) Calculate the average current (IAVG), and adjust R7

and R5 to obtain it.

IAVG

=

10(PAVG/10) ρ

1000

(ρ = photodiode responsivity in A/W)

3) Calculate the AC signal current, and adjust the sig-

nal generator to obtain it.

IINPUT = 2 ✕ IAVG(re - 1) / (re + 1)

For example:

1) Emulate a signal with an average power of -20dBm

and an extinction ratio of 10.

2) -20dBm optical power will produce 10µA of aver-

age input current (assume photodiode responsivity

of 1A/W). Install a current meter at JU1. Adjust R7

and R5 until the current is 10µA.

3) The signal amplitude is 2PAVG(re - 1) / (re + 1) =

16µA. To generate this current through the 1500Ω

input resistors, set the signal source to produce an

output level of 16µA ✕ 1500Ω = 24mVp-p.

Noise Measurement

Remove R2 before attempting noise measurements to

minimize input capacitance. With R2 removed the total

capacitance at the IN pin is approximately 0.5pF. Refer

to the Layout Considerations section in the MAX3266/

MAX3267 data sheet for more information.

Table 1. Recommended Resistor Values

EVALUATION KIT

R1, R9

R2, R10

MAX3266EVKIT-SO 1000Ω (0603)

510Ω (0603)

MAX3267EVKIT-SO 200Ω (0402)

1020Ω (composed

of two 510Ω (0402)

resistors)

Table 2. Connections, Adjustments, and Control

CONTROL

VCC

+15V

GND

DESCRIPTION

Supply Voltage Connection (3.0 to 5.5V, 100mA current limit)

Supply Voltage Connection for Photodiode Emulator Circuit (+15V, 25mA)

Connection for Ground

JU1

When shunted, the photodiode emulation circuit is active. This is a convenient location to measure

the emulated photodiode current.

JU2

R5

R7

OUT+, OUT-

INPUT

Test Pin. Shunting JU2 disables the MAX3266/MAX3267 DC cancellation amplifier.

Potentiometer. Fine adjustment of the DC current input.

Potentiometer. Coarse adjustment of the DC current input.

Connections for the MAX3266/MAX3267 Output Signal

Input Connection for a Signal Generator

2 _______________________________________________________________________________________

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