Broadcom

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Introduction

The AS37-H39B series encoder is a high-resolution optical

absolute encoder produced by Broadcom®, which offers 23-bit

single-turn and 16-bit multi-turn counts, hence a combined

39-bit high resolution. The AS37-H39B series encoder is a

house encoder consisting of a patterned disk, a light source,

and photosensitive elements to translate the mechanical

motion into electrical signal.

The AS37-H39B series encoder has a built-in communication

protocol that is supported by a full-duplex or half-duplex line

transmissions drive, offering good noise immunity for more

robust transmission of data up to 10 Mb/s in harsh industrial

application. Because the product is intended for industrial

application, ESD protection circuitry has been designed in to

achieve Class 3 ESD immunity per IEC -61000-4-2 standard. The

AS37-H39B series is also compliant with IP40 per IEC 60529

standard.

The key advantage of the AS37-H39B series is multi-turn

tracking employs battery backup technology. It is gearless

multi-turn counting that eliminates the gear wear-out or

acoustics noise issue that is encountered in conventional

geared multi-turn encoder.

Operating Theory

Structures-wise, the encoder contains two main functional

blocks: the single-turn optical engine block and the battery

backup multi-turn counter block. The single-turn engine

comprises the Broadcom developed high-performance optical

detector ASIC, which is accompanied by high-precision

amplifiers circuitry, coupled with a special multi-track code disk

that rotates between the LED emitter and detector IC.

On the multi-turn side, the multi-turn counting is enabled

utilizing battery backup counter technology. During battery

mode (encoder operates in main power OFF state), the battery

backup circuitry periodically powers up the LED emitter and

enables the photo sensor to scan the code disk multi-turn

tracks for detection of shaft rotation. In order to prolong the

battery life, extra effort has been put in the design of the ASIC

to ensure minimum current consumption during battery mode

operation. Therefore, no miscounts occur even in the absence

of external power supply.

Features



39-bit resolution: 16-bit battery backup multi-turn and

23-bit optical single-turn



Built-in communication protocol (option): BiSS C mode, SSI

mode and RS-485 half-duplex



Overall encoder outer diameter Ø37 mm and typical

mounting height 28 mm



Supporting standard hollow taper shaft, short hollow

taper shaft and ¼ inch, 6-mm and 8-mm diameter of the

hollow blind shaft options.

Benefits



High resolution with higher measurement accuracy and

better speed ripple control.



Immediate position detection upon power up without the

need of system homing.



Hollow taper shaft design for China Servo motor market.



Short hollow taper shaft option for low height application.



Small OD and low height for ease of integration to small

size motor.

Applications



Robotics



Factory automation



CNC machine tool

NOTE

Broadcom encoders are not recommended

for use in safety critical applications, e.g., ABS

braking systems, power steering, life support

systems, and critical care medical equipment.

Contact a sales representative if more

clarification is needed.

AS37-H39B Series

39-Bit Battery Backup Multi-Turn Absolute Encoder

Data Sheet