Datasheet

to either the GAIN or ATT setting. Table 2 provides typi-
cal output common-mode voltages for the combination
of settings. Settling time is proportional to the RC time
constant set by the output DC-blocking capacitor, load,
and MAX3806 output impedance. For example, a 0.01μF
DC-blocking capacitor, 2kΩ load, and 51Ω output imped-
ance provide an RC time constant of approximately 20μs.
After changing the GAIN or ATT setting, the system
should wait at least three to four time constants before
analyzing received signals.
Settling time is also required when changing the DIS set-
ting. When DIS is asserted high, the output disables to
high impedance and typically settles to steady state within
200ns. When DIS is deasserted, the output enables and
typically settles to steady state within 50ns.
Overload Recovery Time
Transistors saturate when the amplifier is overloaded,
resulting in output distortion. Overload typically occurs
with signals greater than 20μA
P
(GAIN = 1) or 40μA
P
(GAIN = 0). It can withstand overload signals as large
as 2mA
P
. Recovery time depends on the amplitude and
duration of the overload pulse.
Layout Considerations
Noise performance and bandwidth are adversely affected
by capacitance at the IN pad. Minimize capacitance
on this pad and select a low-capacitance photodiode.
Reducing PCB capacitance can be accomplished by
removing the ground plane underneath the connection
from the photodiode to the IN pin and by keeping the pho-
todiode as close as possible to the MAX3806.
Use broadband power-supply filtering techniques to
achieve the best sensitivity and noise performance.
Exposed-Pad Package and Thermal
Considerations
The exposed pad on the 12-pin TQFN provides a very low
thermal resistance path for heat removal from the IC. The
pad is also electrical ground on the MAX3806 and must
be soldered to the circuit board ground for proper thermal
and electrical performance. Refer to Application Note 862:
HFAN-08.1: Thermal Considerations of QFN and Other
Exposed-Paddle Packages for additional information.
Figure 1. Equivalent Output Circuit
Table 2. Output Common-Mode Voltages
GAIN ATT OUTPUT COMMON-MODE VOLTAGE (V)
0 0 1.65
0 1 0.33
1 0 1.82
1 1 0.36
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
12 TQFN-EP T1233+3 21-0136
V
CC
400 OUT
100
200
V
CC
MAX3806
GND GAIN
3
7
IN N.C.
2
8
V
CC
OUT
1
9
12 4V
CC
GND
11 5N.C. ATT
10 6 N.C.DIS
THIN QFN
(3mm
¥ 3mm)
TOP VIEW
+
*EP
*EXPOSED PAD
MAX3806 Receiver for Optical Distance Measurement
www.maximintegrated.com
Maxim Integrated │ 8
Pin Conguration
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.