DS8921_15 Datasheet, PDF (8/20 Pages) Texas Instruments – Differential Line Driver and Receiver Pair

DS8921, DS8921A, DS8921AT
SNLS374D – MAY 1998 – REVISED JANUARY 2015
8 Detailed Description
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8.1 Overview
The DS8921x devices are each a differential line driver and receiver pair in a single package. The devices are
designed specifically for ST506, ST412, and ESDI disk drive standards, as well as RS-422 interface applications.
The DS8921 and DS8921A are rated at a commercial temperature range of 0°C to 70°C, whereas the
DS8921AT is rated at an extended temperature range of -40°C to +85°C.
8.2 Functional Block Diagram
RI+
RO
RI-
DI
5.0 V
VCC
0.1 µF
DO+
DO-
GND
8.3 Feature Description
The DS8921x devices each contain a differential driver and receiver.
The driver converts a TTL or CMOS input to complementary outputs that provide differential drive to a twisted-
pair or parallel wire transmission line. The receiver converts the differential signals at its input pins to a TTL
output. The receiver offers an input sensitivity of ±200 mV and supports a common-mode input voltage of ±7 V.
8.4 Device Functional Modes
Table 1. Function Table
INPUT
RI+, RI-
V_ID(1) ≥ V_TH (MAX)
V_ID(1) ≤ V_TH (MIN)
Open
RECEIVER
OUTPUT
RO
1
0
1
INPUT
DI
1
0
(1) V_ID is the input differential voltage between RI+ and RI–.
DRIVER
OUTPUT
DO+
DO-
1
0
0
1
8
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