MAX14890E
Incremental Encoder Interface for RS-422,
HTL, and TTL with Digital Inputs
General Description
The MAX14890E incremental encoder receiver contains
four differential receivers and two single-ended receivers.
Benefits and Features
● High Flexibility Supports All Encoder Types
• Selectable RS-422/HTL/TTL/DI Receivers
• RS-422/TTL Switching Rates Up to 35Mbps
• HTL Switching Rates Up to 400kHz
The differential receivers can be operated in RS-422 or
differential high-threshold logic (HTL) modes and are
optionally configurable for single-ended TTL/HTL operation.
The MAX14890E features a wide common mode input
range of -20V to +20V in RS-422 mode.
• SPI or Pin-Controlled Operation
• SPI Interface Allows Per-Receiver Configuration
• 1.62V to 5.5V Logic Interface
● Integrated Fault Detection Reduces Down-Time
• Open-Wire and Short-Circuit Detection
The auxiliary IEC 61131-2 Type-1/Type-3 digital inputs
are designed for operation with switches or proximity
sensors and can be individually configured for TTL operation.
• Overvoltage and Undervoltage Fault Detection
● Integrated Protection Ensures Robust
Communication
All receiver input signals are fault protected to voltage shorts
in the ±40V range. Per channel fault detection provides
warning of irregular conditions such as small differential
signals, shorts, opens, overvoltages, and undervoltages.
• ±40V Fault Protection Range
• ±20V RS-422 Common Mode Range
• DI Glitch Filters
The MAX14890E features a pin-selectable SPI or parallel-
logic interface. SPI control provides detailed diagnostics
and individual configurations for receivers.
• ±25kV HBM ESD
• ±7kV Air-Gap per IEC 61000-4-2 ESD
• ±10kV Contact per IEC 61000-4-2 ESD
• -40°C to +125°C Operating Temperature Range
The MAX14890E is available in a 32-pin TQFN-EP (5mm
x 5mm) and operates over the -40°C to +125°C tempera-
ture range.
Applications
● Encoder Interfaces
● Motor Controllers
● Pulse Counters
Ordering Information appears at end of data sheet.
● Servo Control Commutation
Typical Operating Circuit
3.3V to 5V
5V
VCC
Input Receiver Modes
VL
ENCODER
MODE
RS-422
D-HTL
SE-HTL
TTL
RxA RxB RxZ RxY RxDI2 RxDI3
A
A
B
B
AO
RxA
RxB
RS-422 A
RS-422 B
RS-422 Z
120Ω
120Ω
5V
5V
5V
5V
√
√
√
√
√
√
√
√
√
√
√
√
√
√
AFAULT
BO
BFAULT
Z
ZO
ZFAULT
YO
RxZ
RxY
120Ω
Z
√
√
√
√
√
√
DIY
DI
ASIC
TTL ALARM
DO
YFAULT
LO2
DI2
DI3
PROXIMITY
SENSOR
RxD2
DO
LO3
PROXIMITY
SENSOR
RxD3
SNGL/CLK = 0
TTL/SDI = 1
DI/TTLY = 1
DI/TTL2 = 1
DI/TTL3 = 1
MAX14890
COUNTER/
MOTOR
CONTROLLER
ENCODER CIRCUIT WITH RS-422 SIGNALS AND TTL ALARM SIGNAL
19-7536; Rev 0; 3/15