Datasheet

Detailed Description
The MAX3806 preamplifier consists of a selectable-gain
transimpedance amplifier, a selectable 14dB attenu-
ator, and an output-driver block. The selectable-gain
transimpedance amplifier linearly boosts the signal from
the photodiode. This block is followed by an attenuator
block that allows the user to attenuate the signal by 14dB
selected by the ATT pin. The final block is the output
driver that can be disabled by asserting the DIS pin.
Transimpedance Amplier
The selectable-gain transimpedance amplifier is con-
trolled by the GAIN pin. See Table 1 for gain settings.
Attenuator
The attenuator block can be set to pass the signal through
to the output stage with 0dB of attenuation (ATT forced
low) or with 14dB of attenuation (ATT forced high).
Output Driver
The output driver is designed to drive an AC-coupled load
with an impedance of 2kΩ or greater. The output can be
disabled by asserting the DIS pin high. When the output
is disabled, the OUT pin goes to a highimpedance state.
See Figure 1 for the equivalent output circuit.
WARNING: The output is designed to be AC-coupled to
a high-impedance load. Operating the part with its output
DC-coupled to GND through a 2kΩ or less load may dam-
age the output.
Applications Information
Settling Time
Settling time is the required time for the output to achieve
the final steady-state or AC amplitude swing after a set-
ting has been changed on the MAX3806. The output
common-mode voltage shifts when a change is made
Table 1. Transimpedance Gain Settings
PIN NAME FUNCTION
1, 12 V
CC
5V Power-Supply Connection
2 IN Amplier Input. Accepts AC-coupled photodiode input current.
3, 4 GND Supply Ground
5 ATT
CMOS/TTL Input. Assert this pin high to enable a 14dB attenuator in the amplier. Force this pin low
to disable the attenuator. Contains internal 40kΩ pulldown resistor. Connect to GND if not used.
6, 8, 11 N.C. Not Connected. This pin is not internally connected.
7 GAIN
CMOS/TTL Input. Selects amplier gain setting. Force high for 60kΩ. Force low for 30kΩ. Contains
internal 40kΩ pulldown resistor.
9 OUT
Amplier Output. An increase in current into the IN pin causes the voltage at the OUT pin to
decrease. OUT must be AC-coupled to a load of 2kΩ or greater.
10 DIS
CMOS/TTL Input. Force high to disable the output of the MAX3806. Force low to enable the output.
Contains internal 60kΩ pullup resistor.
— EP
Exposed Pad. The exposed pad must be soldered to circuit board ground for proper thermal and
electrical performance.
GAIN TRANSIMPEDANCE (kΩ) LINEAR RANGE (μA
P
) BANDWIDTH (MHz)
0 30 I
IN
≤ 40 98
1 60 I
IN
≤ 20 49
MAX3806 Receiver for Optical Distance Measurement
www.maximintegrated.com
Maxim Integrated │ 7
Pin Description