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19-4700; Rev 0; 7/09
Receiver for Optical Distance Measurement
General Description
The MAX3806 is a high-gain linear preamplifier for distance measurement applications using a laser beam. The device operates from a single +5.0V supply and converts current from an AC-coupled photodiode into a single-ended voltage signal. The input accepts single pulses or bursts of pulses with widths down to 30ns. The amplifier remains linear with input amplitudes from 42nAP (SNR = 3) to 40AP. It can also withstand overload signals as large as 2mAP. The output stage is designed to drive a high-impedance load to deliver the output-voltage swing at the lowest possible power dissipation. The gain of the preamplifier stage is selected using the GAIN pin to be 60k or 30k. There is also an internal 14dB attenuator that is selected using the ATT pin. The output stage can be disabled (high impedance). The device is available in a 3mm x 3mm, 12-pin TQFN package and operates over the -40C to +105C temperature range. +5V Supply Voltage Linearity Range Up to 40AP Overload Current Up to 2mAP 50mW Power Dissipation at +5.0V 1.5pA/Hz Noise Density at 60k Gain 14nARMS Input-Referred Noise at 60k Gain Selectable Gains (60k, 30k) Selectable 14dB Attenuation
Features
MAX3806
Ordering Information
PART TEMP RANGE PINPACKAGE TOP MARK ABN
MAX3806GTC+ -40C to +105C 12 TQFN-EP* +Denotes a lead(Pb)-free/RoHS-compliant package. *EP = Exposed pad.
Applications
LIDAR Sensors for Automotive Applications (ACC, Stop&Go) Laser Sensors for Portable Distance Measurement Laser Sensors for Industrial Applications
Pin Configuration appears at end of data sheet.
Typical Application Circuits
+5V +5V TO +12V SUPPLY FILTER PIN IN C* L* GAIN +5V * L AND C SET THE LOW-FREQUENCY CUTOFF REQUIRED FOR THE APPLICATION. DIS ATT GND SUPPLY FILTER VCC 0.01F 0.01F SINGLE-CHANNEL RECEIVER
MAX3806
LINEAR LIDAR Rx
OUT
BUFF 0.01F
MAX1446
ADC
Typical Application Circuits continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
Receiver for Optical Distance Measurement MAX3806
ABSOLUTE MAXIMUM RATINGS
Supply Voltage Range, VCC........................................-0.5V to +6.0V Voltage Range at ATT, DIS, GAIN ................-0.5V to (VCC + 0.5V) Current Range at IN, OUT ...........................................-4mA to +4mA Continuous Power Dissipation (TA = +70C) 12-Pin TQFN-EP (derate 16.7mW/C above +70C)...1333mW Storage Temperature Range .............................-55C to +150C Lead Temperature (soldering, 10s) .................................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VCC = +4.5V to +5.5V, AC-coupled (C = 0.01F) output load 2k, TA = -40C to +105C. Typical values are at VCC = +5V, TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Power-Supply Current INPUT SPECIFICATIONS Input-Referred Noise CIN = 5pF, GAIN = 1 Output noise up to 100MHz/(gain at 5MHz) CIN = 5pF, GAIN = 0 Output noise centered at 5MHz over 100Hz band/(gain at 5MHz) At 1MHz, GAIN = 1 At 1MHz, GAIN = 0 VIH VIL I IH, I IL I IH RPULLUP DIS input GAIN and ATT inputs DIS input 60 40 44 23 GAIN = 1, ATT = 0 GAIN = 0, ATT = 0 15pF -13 25 55 60 30 49 98 1 -14 -54 -53 -38 -47 -16 -23 dB dB -15 77 37 2 0 CIN = 5pF, GAIN = 1 CIN = 5pF, GAIN = 0 14 21 1.5 1.7 800 300 VCC 0.8 150 -180 V V A k 20 27 1.8 2.3 nARMS SYMBOL ICC (Note 2) CONDITIONS MIN TYP 10 MAX 15 UNITS mA
Input-Referred Noise Density
pA/ Hz
Input Impedance CMOS/TTL INPUT SPECIFICATIONS Input High Voltage Input Low Voltage Input Current Input Impedance GENERAL SPECIFICATIONS Small-Signal Transimpedance Small-Signal Bandwidth Gain Peaking Attenuation Stability OUTPUT SPECIFICATIONS f3dB
RPULLDOWN GAIN and ATT inputs I IN I IN 15AP, GAIN = 1 50AP, GAIN = 0
k MHz dB dB
CIN = 5pF 5pF C IN
ATT = 1; 20log(VOUT_ATT_ON/VOUT_ATT_OFF) Frequency = 1MHz, VOUT = 0.5VP Frequency = 10MHz, VOUT = 0.5VP GAIN = 1 GAIN = 0 GAIN = 1 GAIN = 0 GAIN = 1 GAIN = 0
Total Harmonic Distortion
THD
Power-Supply Noise Rejection (Note 3)
PSNR
Noise frequency < 1MHz
2
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Receiver for Optical Distance Measurement
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +4.5V to +5.5V, AC-coupled (C = 0.01F) output load 2k, TA = -40C to +105C. Typical values are at VCC = +5V, TA = +25C, unless otherwise noted.) (Note 1)
PARAMETER Attenuation in Disable Mode SYMBOL CONDITIONS Frequency < 5MHz, 20log(VOUT_DISABLED/ VOUT_ENABLED) ATT = 0 ATT = 1 MIN TYP -71 dB -57 51 114 9 k MAX UNITS
MAX3806
At 1MHz, DIS = 0, ATT = 0, GAIN = 0 or 1 Output Impedance At 1MHz, DIS = 0, ATT = 1, GAIN = 0 or 1 At 1MHz, DIS = 1, ATT = 0 or 1, GAIN = 0 or 1
Note 1: AC specifications are guaranteed by design and characterization. Note 2: Supply current is measured with OUT unterminated or AC-coupled. Note 3: Measured by applying 100mVP-P sinusoidal noise to the supply voltage. PSNR is defined as 20log(VOUT_NOISE/VCC_NOISE).
Typical Operating Characteristics
(Typical values are at VCC = +5V, TA = +25C, CIN = 5pF, ATT = 0, unless otherwise noted.)
SUPPLY CURRENT vs. TEMPERATURE
MAX3806 toc01
OUTPUT VOLTAGE vs. INPUT CURRENT
MAX3806 toc02
FREQUENCY RESPONSE
100 TRANSIMPEDANCE (dBI) 95 90 85 80 75 70 65 GAIN = 0, ATT = 1 GAIN = 0, ATT = 0 GAIN = 1, ATT = 1
MAX3806 toc03
16 14 SUPPLY CURRENT (mA) 12 10 8 6 4 2 0 -40 -15 10 35 60 85 DIS = 1 DIS = 0
10 GAIN = 1, ATT = 0 OUTPUT VOLTAGE (VP) 1 GAIN = 0, ATT = 0 0.1 GAIN = 1, ATT = 1 0.01 GAIN = 0, ATT = 1 0.001
105 GAIN = 1, ATT = 0
110
0.1
1
10
INPUT CURRENT (AP)
100
1000
60 0.1 1 10 100
FREQUENCY (MHz)
TEMPERATURE (NC)
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Receiver for Optical Distance Measurement MAX3806
Typical Operating Characteristics (continued)
(Typical values are at VCC = +5V, TA = +25C, CIN = 5pF, ATT = 0, unless otherwise noted.)
BANDWIDTH vs. INPUT CAPACITANCE (GAIN = 1)
MAX3806 toc04
BANDWIDTH vs. INPUT CAPACITANCE (GAIN = 1)
VCC = +5.5V VCC = +5.0V TA = +25NC
MAX3806 toc05
GAIN PEAKING vs. INPUT CAPACITANCE
MAX3806 toc06
60 50 BANDWIDTH (MHz) 40 30 20 10 0 5 7 9 11 13 TA = +105 NC TA = -40 NC TA = +25 NC VCC = +5.0V
60 50 BANDWIDTH (MHz) 40 30 20 10 0 VCC = +4.5V
1.0 0.8 GAIN PEAKING (dB) 0.6 0.4 0.2 GAIN = 1 0
GAIN = 0
15
5
7
9
11
13
15
5
7
9
11
13
15
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
BANDWIDTH vs. INPUT CAPACITANCE (GAIN = 0)
MAX3806 toc07
BANDWIDTH vs. INPUT CAPACITANCE (GAIN = 0)
MAX3806 toc08
POWER-SUPPLY NOISE REJECTION (SUPPLY NOISE = 100mVP-P)
GAIN = 1, ATT = 0 GAIN = 0, ATT = 0 -10 PSNR (dB) -20 -30 -40 -50 -60 GAIN = 0, ATT = 1 GAIN = 1, ATT = 1 0
MAX3806 toc09
120 VCC = +5V 100 BANDWIDTH (MHz) 80 60 40 20 0 5 7 9 11 13 TA = -40NC TA = +25NC TA = +105NC
120 TA = +25NC 100 BANDWIDTH (MHz) 80 60 40 20 0 VCC = +4.5V VCC = +5.5V VCC = +5.0V
10
15
5
7
9
11
13
15
10k
100k
1M
10M
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
FREQUENCY (Hz)
INPUT-REFERRED NOISE vs. INPUT CAPACITANCE
MAX3806 toc10
INPUT-REFERRED NOISE vs. INPUT CAPACITANCE
MAX3806 toc11
OUTPUT-REFERRED NOISE vs. INPUT CAPACITANCE
OUTPUT-REFERRED NOISE (VRMS) 950 900 850 800 750 700 650 600 VCC = +4.5V VCC = +5.0V TA = +25NC GAIN = 1 BW = 100MHz VCC = +5.5V
MAX3806 toc12
16 INPUT-REFERRED NOISE (nARMS) 15 14 13 12 11 10 5 7
VCC = +5V
16 INPUT-REFERRED NOISE (nARMS) 15 14 13 12
GAIN = 1 BW = 100MHz
TA = +25NC
1000
GAIN = 1 BW = 100MHz VCC = +5.5V
TA = +105NC TA = -40NC
VCC = +5.0V VCC = +4.5V
TA = +25NC
11 10
9
11
13
15
5
7
9
11
13
15
5
7
9
11
13
15
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
4
_______________________________________________________________________________________
Receiver for Optical Distance Measurement
Typical Operating Characteristics (continued)
(Typical values are at VCC = +5V, TA = +25C, CIN = 5pF, ATT = 0, unless otherwise noted.)
MAX3806
INPUT-REFERRED NOISE vs. INPUT CAPACITANCE
MAX3806 toc13
INPUT-REFERRED NOISE vs. INPUT CAPACITANCE
OUTPUT-REFERRED NOISE (VRMS) 25 24 23 22 21 20 19 18 450 5 7 9 11 13 15 5 VCC = +4.5V TA = +25NC VCC = +5.5V GAIN = 0 BW = 100MHz
MAX3806 toc14
OUTPUT-REFERRED NOISE vs. INPUT CAPACITANCE
TA = +25NC 650 600 550 500 VCC = +5.5V VCC = +5.0V GAIN = 0 BW = 100MHz
MAX3806 toc15
26 INPUT-REFERRED NOISE (nARMS) 25 24 23 22 21 20 19 18 5 7
VCC = +5V TA = +105NC
INPUT-REFERRED NOISE (nARMS)
GAIN = 0 BW = 100MHz
26
700
TA = +25NC
VCC = +5.0V
VCC = +4.5V
TA = -40NC
9
11
13
15
7
9
11
13
15
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
INPUT CAPACITANCE (pF)
TOTAL HARMONIC DISTORTION vs. FREQUENCY
VOUT = 0.5VP -10 -20 THD (dB) GAIN = 1 -30 -40 -50 -60 0.1 1 10 100 GAIN = 0 OUT (200mV/div)
MAX3806 toc16
DISABLE SWITCH (DC-BLOCK = 0.01F, LOAD = 2kI)
MAX3806 toc17
0
DIS (5V/div)
100ns/div
FREQUENCY (MHz)
GAIN SWITCH (DC-BLOCK = 0.01F, LOAD = 2kI)
MAX3806 toc18
ATT SWITCH (DC-BLOCK = 0.01F, LOAD = 2kI)
MAX3806 toc19
GAIN (5V/div)
ATT (5V/div)
OUT (200mV/div)
OUT (500mV/div)
40s/div
40s/div
_______________________________________________________________________________________
5
Receiver for Optical Distance Measurement MAX3806
Typical Operating Characteristics (continued)
(Typical values are at VCC = +5V, TA = +25C, CIN = 5pF, ATT = 0, unless otherwise noted.)
TRANSIENT RESPONSE (LINEAR REGION, GAIN = 1)
MAX3806 toc20
TRANSIENT RESPONSE (OVERLOAD REGION, GAIN = 1)
MAX3806 toc21
TRANSIENT RESPONSE (OVERLOAD REGION, GAIN = 1)
MAX3806 toc22
ZOOM IN 1AP IN OUT 60mVP 20MHz BW LIMIT 20ns/div 100ns/div IN 2mAP IN 2mAP
ZOOM OUT
OUT 1.4VP 20MHz BW LIMIT
OUT 60s SETTLING TIME 1.4VP 0.01F DC-BLOCK 2kI LOAD 10s/div
Functional Diagram
MAX3806
IN ATTENUATOR VCC 60k OUT
SWITCHABLE IMPEDANCE 60k OR 30k
40k
40k
GAIN
ATT
DIS
6
_______________________________________________________________________________________
Receiver for Optical Distance Measurement
Pin Description
PIN 1, 12 2 3, 4 5 6, 8, 11 7 9 10 -- NAME VCC IN GND ATT N.C. GAIN OUT DIS EP 5V Power-Supply Connection Amplifier Input. Accepts AC-coupled photodiode input current. Supply Ground CMOS/TTL Input. Assert this pin high to enable a 14dB attenuator in the amplifier. Force this pin low to disable the attenuator. Contains internal 40k pulldown resistor. Connect to GND if not used. Not Connected. This pin is not internally connected. CMOS/TTL Input. Selects amplifier gain setting. Force high for 60k . Force low for 30k . Contains internal 40k pulldown resistor. Amplifier 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 2k or greater. CMOS/TTL Input. Force high to disable the output of the MAX3806. Force low to enable the output. Contains internal 60k pullup resistor. Exposed Pad. The exposed pad must be soldered to circuit board ground for proper thermal and electrical performance. FUNCTION
MAX3806
Detailed Description
The MAX3806 preamplifier consists of a selectable-gain transimpedance amplifier, a selectable 14dB attenuator, 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.
Output Driver
The output driver is designed to drive an AC-coupled load with an impedance of 2k 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 2k or less load may damage the output.
Transimpedance Amplifier
The selectable-gain transimpedance amplifier is controlled by the GAIN pin. See Table 1 for gain settings.
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 setting has been changed on the MAX3806. The output common-mode voltage shifts when a change is
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).
Table 1. Transimpedance Gain Settings
GAIN 0 1 TRANSIMPEDANCE (k ) 30 60 LINEAR RANGE (AP) I IN I IN 40 20 BANDWIDTH (MHz) 98 49
_______________________________________________________________________________________
7
Receiver for Optical Distance Measurement MAX3806
Layout Considerations
VCC 200
VCC
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 photodiode as close as possible to the MAX3806. Use broadband power-supply filtering techniques to achieve the best sensitivity and noise performance.
OUT
400
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.
100
Figure 1. Equivalent Output Circuit
made to either the GAIN or ATT setting. Table 2 provides typical 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 0.01F DC-blocking capacitor, 2k load, and 51 output impedance provide an RC time constant of approximately 20s. 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 setting. 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.
Pin Configuration
TOP VIEW
OUT 9 DIS 10 N.C. 8
GAIN 7 6 N.C. 5
N.C. 11
MAX3806
+
1 VCC 2 IN *EP 3 GND
ATT
VCC 12
4
GND
Overload Recovery Time
Transistors saturate when the amplifier is overloaded, resulting in output distortion. Overload typically occurs with signals greater than 20AP (GAIN = 1) or 40AP (GAIN = 0). It can withstand overload signals as large as 2mAP. Recovery time depends on the amplitude and duration of the overload pulse.
THIN QFN (3mm x 3mm)
*EXPOSED PAD
Table 2. Output Common-Mode Voltages
GAIN 0 0 1 1 ATT 0 1 0 1 OUTPUT COMMON-MODE VOLTAGE (V) 1.65 0.33 1.82 0.36
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 12 TQFN-EP PACKAGE CODE T1233+1 DOCUMENT NO. 21-0136
8
_______________________________________________________________________________________
Receiver for Optical Distance Measurement
Typical Application Circuits (continued)
+5V +5V TO +12V SUPPLY FILTER PIN IN C* L* GAIN +5V MULTIPLE-CHANNEL RECEIVER DIS0 +5V +5V TO +12V SUPPLY FILTER PIN IN C* L* GAIN +5V DIS1 +5V +5V TO +12V SUPPLY FILTER PIN IN C* L* GAIN +5V DIS2 +5V +5V TO +12V SUPPLY FILTER PIN IN C* L* GAIN +5V DIS3 * L AND C SET THE LOW-FREQUENCY CUTOFF REQUIRED FOR THE APPLICATION. DIS ATT GND SUPPLY FILTER +5V VCC 7k 0.01F DIS3 DIS0 DIS1 DIS2 DIS ATT GND SUPPLY FILTER +5V VCC 7k 0.01F A0 A1 DIS ATT GND SUPPLY FILTER +5V VCC 7k 0.01F +5V DIS ATT GND SUPPLY FILTER +5V VCC 7k 0.01F
MAX3806
MAX3806
LINEAR LIDAR Rx
OUT 3k
MAX3806
LINEAR LIDAR Rx
OUT 3k
MAX4311
4:1 MUX/AMP IN0 IN1 IN2 IN3 0.01F 0.01F BUFF 0.01F
MAX1446
ADC
MAX3806
LINEAR LIDAR Rx
OUT 3k
MAX3806
LINEAR LIDAR Rx
OUT MICROCONTROLLER/DSP 3k
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9
(c) 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.

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