DS8921/DS8921A/DS8921AT Differential Line Driver and Receiver Pair
May 1998
DS8921/DS8921A/DS8921AT
Differential Line Driver and Receiver Pair
General Description
The DS8921, DS8921A are Differential Line Driver and Re-
ceiver pairs designed specifically for applications meeting
the ST506, ST412 and ESDI Disk Drive Standards. In addi-
tion, these devices meet the requirements of the EIA Stan-
dard RS-422.
The DS8921, DS8921A receivers offer an input sensitivity of
200 mV over a
±
7V common mode operating range. Hyster-
esis is incorporated (typically 70 mV) to improve noise mar-
gin for slowly changing input waveforms.
The DS8921, DS8921A drivers are designed to provide uni-
polar differential drive to twisted pair or parallel wire trans-
mission lines. Complementary outputs are logically ANDed
and provide an output skew of 0.5 ns (typ.) with propagation
delays of 12 ns.
The DS8921, DS8921A are designed to be compatible with
TTL and CMOS.
Features
n
n
n
n
n
12 ns typical propagation delay
Output skew - 0.5 ns typical
Meet the requirements of EIA Standard RS-422
Complementary Driver Outputs
High differential or common-mode input voltage ranges
of
±
7V
n
±
0.2V receiver sensitivity over the input voltage range
n
Receiver input hysteresis-70 mV typical
n
DS8921AT industrial temperature
operation: (−40˚C to +85˚C)
Connection Diagram
DS008512-1
Order Number DS8921M, DS8921N, DS8921AM, DS8921AN,
DS8921ATM, or DS8921ATN
See NS Package Number M08A or N08E
Truth Table
Receiver
Input
V
ID
≥
V
TH
(MAX)
V
ID
≤
V
TH
(MIN)
Open
V
OUT
1
0
1
Input
1
0
Driver
V
OUT
1
0
V
OUT
0
1
© 1998 National Semiconductor Corporation
DS008512
www.national.com
NSC [ NATIONAL SEMICONDUCTOR ]
