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MAXREFDES_LIDAR1#: Quad-Channel LiDAR Receiver Front-End Reference Design, MAX40662, MAX40026

MAXREFDES-LIDAR1

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Description

Maxim Integrated partnered with First Sensor to design a reference design featuring the First Sensor 4-channel APD array, Maxim quad TIA with multiplexer MAX40662, and Maxim single fast comparator MAX40026.

This document highlights how easy it is to interface these three critical components when designing the front end of a receiver in a light detection and ranging (LiDAR) module. The MAX400662 and MAX40026 are AEC-Q100 qualified. So, these are highly suitable for automotive applications. These can be used in any industrial or commercial applications needing LiDAR.

This document provides some tips and recommendations seamlessly applied to systems with a higher count of channels.

Features

  • 4-Channel APD
  • Quad Channel TIA with MUX
  • Single Fast Comparator

  • maxrefdes-lidar

    maxrefdes-lidar

  • MAXREFDES_LIDAR1# -  MAXREFDES_LIDAR1# Quad-Channel LiDAR Receiver Front-End Reference Design, MAX40662, MAX40026

    MAXREFDES_LIDAR1# - MAXREFDES_LIDAR1# Quad-Channel LiDAR Receiver Front-End Reference Design, MAX40662, MAX40026

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Designed, Built, Tested

Board pictured here has been fully assembled and tested.

 

Details Section

Details Section

The quad-channel LiDAR receiver front-end reference design features a 4-channel avalanche photodiode (APD) array from First Sensor, interfacing the Maxim Quad TIA MAX40062 and Maxim single fast comparator MAX40026.

The reference design implements test points to check each part of the board independently. Table 1 describes each critical piece of the board in detail with a focus on how to interface the APD to the trans-impedance amplifier (TIA) and the TIA to the comparator.

A special paragraph is dedicated to the layout recommendations.

Table 1. Bill of Materials

Designation Qty Description
C1, C19 2 CAPACITOR; SMT (0402); CERAMIC CHIP; 100PF; 50V; TOL=5%; TG=-55 DEGC TO +125 DEGC; TC=C0G
C2 1 CAPACITOR; SMT (0402); CERAMIC CHIP; 2200PF; 50V; TOL=10%; TG=-55 DEGC TO +125 DEGC; TC=X7R
C3 1 CAPACITOR; SMT (0402); CERAMIC CHIP; 1UF; 10V; TOL=10%; MODEL=; TG=-55 DEGC TO +85 DEGC; TC=X5R
C4, C10, C11 3 CAPACITOR; SMT (0402); CERAMIC; 0.1UF; 16V; TOL=10%; MODEL=GRM SERIES; TG=-55 DEGC to +85 DEGC; TC=X5R
C5 1 CAPACITOR; SMT; 0402; CERAMIC;  2.2uF; 6.3V; 20%; X5R; -55degC to + 85degC; 0 +/-15% degC MAX.
C20-C23 4 CAPACITOR; SMT (0402); CERAMIC CHIP; 0.1UF; 50V; TOL=10%; TG=-55 DEGC TO +125 DEGC; TC=X7R
C24 1 CAPACITOR; SMT (0402); CERAMIC CHIP; 2.2UF; 35V; TOL=20%; MODEL=C SERIES; TG=-55 DEGC TO +85 DEGC; TC=X5R
C25 1 CAPACITOR; THROUGH HOLE-RADIAL LEAD; ALUMINUM-ELECTROLYTIC; 3.3UF; 400V; TOL=20%; TG=-40 DEGC TO +85 DEGC
C9 1 CAPACITOR, 1nF
CIN1, CIN3, CIN5, CIN7 4 CAPACITOR; SMT; 0402; CERAMIC;  100pF; 50V; 10%; C0G; -55degC to + 125degC; 0 +/-30PPM/degC
CIN2, CIN4, CIN6, CIN8 4 CAPACITOR; SMT (0402); CERAMIC CHIP; 0.1UF; 25V; TOL=10%; MODEL=GRM SERIES; TG=-55 DEGC TO +125 DEGC; TC=X7R
GND1-GND4, J5, V1_SUPPLY, VCC 7 EVK KIT PARTS; MAXIM PAD; WIRE; NATURAL; SOLID; WEICO WIRE; SOFT DRAWN BUS TYPE-S; 20AWG
IN1-IN4, J6, J7, OUTN, OUTP 8 CONNECTOR; FEMALE; SMT; SMA JACK PCB; RIGHT ANGLE; 2PINS
I_OFFSET, LP, SEL0, SEL1 4 CONNECTOR; MALE; THROUGH HOLE; SMB JACK VERTICAL PCB MOUNT; STRAIGHT; 5PINS
J1 1 CONNECTOR; MALE; THROUGH HOLE; BREAKAWAY; STRAIGHT THROUGH; 3PINS; -65 DEGC TO +125 DEGC
J2-J4 3 CONNECTOR; MALE; THROUGH HOLE; BREAKAWAY; STRAIGHT; 4PINS
L1 1 INDUCTOR; SMT (0402); FERRITE-BEAD; 600; TOL=+/-25%; 0.2A
L2 1 INDUCTOR; SMT (0402); FERRITE-BEAD; 600; TOL=+/-25%; 0.9A
MH1-MH4 4 MACHINE SCREW; SLOTTED; PAN; 4-40IN; 3/8IN; NYLON
MH1-MH4 4 STANDOFF; FEMALE-THREADED; HEX; 4-40IN; 3/8IN; NYLON
R1-R3, R7-R14, RCL 12 RESISTOR; 0402; 0 OHM; 0%; JUMPER; 0.10W; THICK FILM
R4 1 RESISTOR; 0402; 1K; 1%; 100PPM; 0.0625W; THICK FILM
R5 1 RESISTOR; 0805; 10K; 1%; 100PPM; 0.125W; THICK FILM
R6 1 RESISTOR; 0805; 100 OHM; 0.1%; 25PPM; 0.125W; THICK FILM
R15 1 RESISTOR; 0805; 33K; 1%; 100PPM; 0.125W; THICK FILM
R16 1 RESISTOR; 0603; 250 OHM; 0.1%; 25PPM; 0.1W; THIN FILM
R17 1 RESISTOR, 0805, 750 OHM, 1%, 100PPM, 0.125W, THICK FILM
R18 1 RESISTOR; 0603; 402 OHM; 1%; 100PPM; 0.10W; THICK FILM
R19 1 RESISTOR; 0603; 604 OHM; 0.1%; 25PPM; 0.1W; METAL FILM
RT1-RT4 4 RESISTOR; 0402; 49.9 OHM; 0.1%; 25PPM; 0.063W; THICK FILM
SU1-SU4 4 TEST POINT; JUMPER; STR; TOTAL LENGTH=0.24IN; BLACK; INSULATION=PBT;PHOSPHOR BRONZE CONTACT=GOLD PLATED
TP1 1 CONNECTOR; FEMALE; PANELMOUNT; NON-INSULATED RECESSED HEAD BANANA JACK; STRAIGHT THROUGH; 1PIN
U1 1 EVKIT PART - IC; AMP; QUAD TRANSIMPEDANCE AMPLIFIER WITH INPUT CURRENT CLAMP AND MULTIPLEXER FOR LIDAR; PACKAGE OUTLINE DRAWING: 21-100204; PACKAGE CODE: T1644Y+5C; LAND PATTERN: 90-0070; TQFN16-EP
U2 1 EVKIT PART-DIODE; FIRST SENSOR APD ARRAY; SMT; PIV=200V
U3 1 EVKIT PART - IC; MAX40026; PACKAGE OUTLINE: 21-100185; PACKAGE CODE: T822Y+3; TDFN8-EP

Gain Selection Input (GAIN)

The J1 jumper is implemented to adjust the gain of the TIA. Set the gain to 25kΩ or 50kΩ in a static way in the application by connecting the GAIN pin to the GND or VCC permanently or have a dynamic signal controlled by a microprocessor to change the gain on the fly as required in the application. See Table 2 for more details.

Table 2. Jumper Table (J1)

Jumper Shunt Position Description
J1 1 TO 2 Connects GAIN to GND (Gain = 25kΩ)
2 TO 3Connects GAIN to VCC (Gain = 50kΩ)

Table 3. Jumper Table (J2)

Jumper Shunt Position Description
J2 1 TO 2 Connects LP to GND (Low-Power Mode On)
1 TO 3Connects LP to LP External Connector for External Control
1 TO 4Connects LP to VCC (Normal Mode On)

Channel Selection

The SEL0 and SEL1 jumpers are used to select the channel sent to the comparator. The channel selection is static in this reference design. In a normal application, these two pins are connected to a microprocessor to control the channel to output dynamically. See Tables 4 and 5 for more details.

APD Description

A 4-channel APD array for near infrared (NIR) detection of First Sensor is used. It is placed in a ceramic carrier type non-hermetic SMD package with AR-coated glass window. The used APD arrays are engineering samples for LiDAR applications (autonomous driving, industrial, and commercial) with the following technical parameters.

Table 4. Jumper Table (SEL0, SEL1, J1, J2)

Jumper Shunt Position Description
SEL0 1 TO 2 Connects SEL0 to VCC (1) – Refer to Table 5 for Channel Selection Decoding Table
2 TO 3Connects SEL0 to GND (0) – Refer to Table 5 for Channel Selection Decoding Table
SEL0 1 TO 2 Connects SEL1 to VCC (1) – Refer to Table 5 for Channel Selection Decoding Table
2 TO 3Connects SEL1 to GND (0)– Refer to Table 5 for Channel Selection Decoding Table

Table 5. MUX Channel Selection Decoding Table (SEL0, SEL1)

SEL1:SEL0 SELECTED INPUT CHANNEL
00 1
01 2
10 3
11 4

Table 6. Electrooptical Characteristics at 23°C

SYMBOL CHARACTERISTIC TEST CONDITION   TYP MAX UNIT
   No. of Elements   4  
   Active Area  per element 470 x 500 µm
   Gap; Pitch   40 ; 510 µm
ID  Dark Current  M = 100, per element   50 500 pA
C  Capacitance  M = 100, per element, f = 100kHz   0.55   pF
   Responsivity  M = 100, λ = 905nm 52 58   A/W
tR  Rise Time  M = 100 V; λ = 905nm; RL = 50Ω   1.3   Ns
VBR  Breakdown Voltage  IR = 2µA 160 200 240 V
   Cross Talk  λ = 905nm   50   dB
   Temperature Coefficient     1.45   V/K
   Photocurrent Uniformity M = 50   ±2 ±10 %
T AR Coating Cover Glass λ = 905nm, AOI = 0° 99     %

Technical drawingFigure 3. Technical drawing.

APD to TIA Connection

The APD outputs are connected to the TIA in a DC-coupled fashion. There is no need for AC coupling capacitors in this case although it is left to the discretion of designers to select from the AC or DC coupling based on the application requirements. Both schemes are allowed.

Connectors were added in this design to access the TIA independently. These are AC-coupled (Figure 3).

Alternative Input to Bypass APD

The APD array can be bypassed and each TIA input channel can be fed from an external electrical source generator. Unsolder all the four 0Ω resistors R11, R12, R13, and R14, and populate the following resistors with 0Ω: R3, R7, R8, and R10.

TIA to Comparator Connection

The TIA outputs in this design are sent to the comparator inputs in an AC-coupled mode using the C10 and C11 capacitors. Then, R16, R17, R18, and R19 allow to create the necessary offset between IN+ and IN- for the proper operation of the comparator.

Comparator Output

The MAX40026 provides a low-voltage differential signaling (LVDS) output, which can be sent directly to any processing circuit.

4-channel APD schematicsFigure 4. 4-channel APD schematics.

AC-coupled external input to the TIAFigure 5. AC-coupled external input to the TIA.

Interface between the TIA and comparatorFigure 6. Interface between the TIA and comparator.

Quick Start Guide for PC Application

Required Equipment

  • MAXREFDES_LIDAR1#
  • 3.3V/200mA DV Power Supply
  • -50V/200mA DC Power Supply
  • 500MHz Digital Oscilloscope with Two Channels
  • Two Equal Length SMA Cables
  • Light Source (Flashlight)

Procedure

  1. Connect the -50V supply to the -HV and GND banana jacks of the MAXREFDES_LIDAR1 board.
  2. Connect the 3.3V supply to VCC and GND pads of the MAXREFDES_LIDAR1 board.
  3. Verify the shunts are installed on the jumpers according to Table 7.
  4. Connect the SMA cables to OUT+ (J6) and OUT- (J7) connectors of the board to the oscilloscope channels.
  5. Turn on the power supplies.
  6. Apply the light source on U2 of the MAXREFDES_LIDAR1 board (about one inch away).
  7. Monitor the oscilloscope. The OUT+ and OUT should toggle like Figure 7.
  8. Move the shunt of the jumper SEL0 to the 1 to 2 position. Repeat steps 6 and 7.
  9. Move the shunt of the jumper SEL0 to the 2 to 3 position and SEL1 to 1 to 2 position. Repeat steps 6 and 7.
  10. Move the shunt of the jumper SEL1 to the 2 to 3 position. Repeat steps 6 and 7.
  11. The test is complete.

Table 7. Jumper Position

JUMPER SHUNT POSITION
J1 1-2
J2 1-2
SEL0 2-3
SEL1 2-3

OUT+ and OUT- signalFigure 7. OUT+ and OUT- signal.

Schematics

MAXREFDES_LIDAR1#High Resolution Image ›
Figure 8. MAXREFDES_LIDAR1# schematics (1).

MAXREFDES_LIDAR1#High Resolution Image ›
Figure 9. MAXREFDES_LIDAR1# schematics (2). schematics (1).

Layout Recommendations

A 4-layer PCB board is used for this reference design with a high-performance substrate material like Rogers. The top and bottom layers implement all the signals, while layer 2 and 3 are used as ground planes.

The following guidelines are implemented:

  • A differential microstrip is used for the MAX40662 outputs with terminations close to the outputs. Avoid unwanted stubs by removing the ground below the traces not part of the termination line leading into the input pins. The parasitic capacitance created between the traces and ground slow down and even distort the signals by creating reflections on the path.
  • The input trace connecting each of the photo-diode array to the IN_ of the MAX40662 should be as short as possible and have ground etched/removed underneath. This reduces unwanted parasitic capacitance created in the PCB. Longer trace lengths increases the parasitic inductance in the signal trace paths.
  • There are four input traces in the design. It is critical to include a ground isolation between them to minimize channel to channel coupling.
  • Mount one or more ceramic capacitors between the GND and VCC as close to the pins as possible. Multiple bypass capacitors reduce the effect of trace impedance and capacitor ESR.
  • Bypass capacitors are chosen for minimum inductance and ESR.
  • Minimize any parasitic layout inductance by keeping the traces as short as possible.
MAXREFDES_LIDAR1# layout (silk screen)Figure 10. MAXREFDES_LIDAR1# layout (silk screen).

MAXREFDES_LIDAR1# layout (top)Figure 11. MAXREFDES_LIDAR1# layout (top).

MAXREFDES_LIDAR1# layout (ground 2)Figure 12. MAXREFDES_LIDAR1# layout (ground 2).

MAXREFDES_LIDAR1# layout (ground 3)Figure 13. MAXREFDES_LIDAR1# layout (ground 3).

MAXREFDES_LIDAR1# layout (bottom)Figure 14. MAXREFDES_LIDAR1# layout (bottom).

MAXREFDES_LIDAR1# layout (silk bottom)Figure 15. MAXREFDES_LIDAR1# layout (silk bottom).

Parametrics

Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 3.3 - - - - - - -

Parametrics

Input Type DC
Vin(Min) 3.3
Vin(Max) -
Iout(Max) -
Single/Multiple Output -
Vout(V) -
Pout(W) -
Isolated/Non-Isolated -
Topology -

Maxim Devices (2)

Part Number Name Product Family Order Design kits and evaluation modules
MAX40662 Quad Transimpedance Amplifier with Input Current Clamp and Multiplexer for LiDAR Amplifiers Buy Now Design Kits
MAX40026 280ps High-Speed Comparator, Ultra-Low Dispersion with LVDS Outputs Amplifiers Buy Now Design Kits

Maxim Devices (2)

Part Number Product Family
Amplifiers
Quad Transimpedance Amplifier with Input Current Clamp and Multiplexer for LiDAR
Amplifiers
280ps High-Speed Comparator, Ultra-Low Dispersion with LVDS Outputs

Applications

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