NSC DS8921ATMX, DS8921ATM, DS8921AN, DS8921AMX, DS8921AM Datasheet

May 1998

DS8921/DS8921A/DS8921AT

Differential Line Driver and Receiver Pair

General Description

The DS8921, DS8921A are Differential Line Driver and Receiver pairs designed specifically for applications meeting the ST506, ST412 and ESDI Disk Drive Standards. In addition, these devices meet the requirements of the EIA Standard RS-422.

The DS8921, DS8921A receivers offer an input sensitivity of 200 mV over a ±7V common mode operating range. Hysteresis is incorporated (typically 70 mV) to improve noise margin for slowly changing input waveforms.

The DS8921, DS8921A drivers are designed to provide unipolar differential drive to twisted pair or parallel wire transmission 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

n12 ns typical propagation delay

nOutput skew - 0.5 ns typical

nMeet the requirements of EIA Standard RS-422

nComplementary Driver Outputs

nHigh differential or common-mode input voltage ranges of ±7V

n±0.2V receiver sensitivity over the input voltage range

nReceiver input hysteresis-70 mV typical

nDS8921AT industrial temperature operation: (−40ÊC to +85ÊC)

Connection Diagram

DS008512-1

Order Number DS8921M, DS8921N, DS8921AM, DS8921AN,

DS8921ATM, or DS8921ATN

See NS Package Number M08A or N08E

Truth Table

Receiver			Driver
Input	VOUT	Input	VOUT		V	OUT
VID ³ VTH (MAX)	1	1	1	0
VID £ VTH (MIN)	0	0	0	1
Open	1

Pair Receiver and Driver Line Differential DS8921/DS8921A/DS8921AT

© 1998 National Semiconductor Corporation

DS008512

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Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.

Supply Voltage	7V
Driver Input Voltage	−0.5V to +7V
Output Voltage	5.5V
Receiver Output Sink
Current	50 mA
Receiver Input Voltage	±10V
Differential Input Voltage	±12V
Maximum Package Power Dissipation @ +25ÊC
M Package	730 mW
N Package	1160 mW
Derate M Package	9.3 mW/ÊC above +25ÊC
Derate N Package	5.8 mW/ÊC above +25ÊC

Storage Temperature
Range	−65ÊC to +165ÊC
Lead Temperature	+260ÊC
(Soldering, 4 sec.)	+260ÊC
Maximum Junction
Temperature	+150ÊC

Recommended Operating

Conditions

	Min	Max	Units
Supply Voltage	4.5	5.5	V
Temperature (TA)
DS8921/DS8921A	0	70	ÊC
DS8921AT	−40	+85	ÊC

DS8921/DS8921A Electrical Characteristics (Notes 2, 3, 4)

Symbol						Conditions	Min	Typ	Max	Units
RECEIVER
VTH						−7V ≤ VCM ≤ +7V	−200	±35	+200	mV
VHYST						−7V ≤ VCM ≤ +7V	15	70		mV
RIN						VIN = −7V, +7V	4.0	6.0		k Ω
						(Other Input = GND)
IIN						VIN = 10V			3.25	mA
						VIN = −10V			−3.25	mA
VOH						IOH = −400 µA	2.5			V
VOL						IOL = 8 mA			0.5	V
ISC						VCC = MAX, VOUT = 0V	−15		−100	mA
DRIVER
VIH							2.0			V
VIL									0.8	V
IIL						VCC = MAX, VIN = 0.4V		−40	−200	µA
IIH						VCC = MAX, VIN = 2.7V			20	µA
II						VCC = MAX, VIN = 7.0V			100	µA
VCL						VCC = MIN, IIN = −18 mA			−1.5	V
VOH						VCC = MIN, IOH = −20 mA	2.5			V
VOL						VCC = MIN, IOL = +20 mA			0.5	V
IOFF						VCC = 0V, V OUT = 5.5V			100	µA
|VT| ±	|VT			|					0.4	V
VT							2.0			V
|VOS ±		V			|				0.4	V
			OS
ISC						VCC = MAX, VOUT = 0V	−30		−150	mA
DRIVER and RECEIVER
ICC						VCC = MAX, VOUT = Logic 0			35	mA

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Receiver Switching Characteristics

Figure 1(Figure 2)

Symbol	Conditions	Min	Typ		Max		Units
				8921	8921A	8921AT
TpLH	CL = 30 pF		14	22.5	20	20	ns
	(Figures 1, 2 )
TpHL	CL = 30 pF		14	22.5	20	20	ns
	(Figures 1, 2)
|TpLH±T pHL|	CL = 30 pF		0.5	5	3.5	5	ns
	(Figures 1, 2 )

Driver Switching Characteristics

SINGLE ENDED CHARACTERISTICS (Figures 3, 4)

Symbol	Conditions	Min	Typ		Max		Units
				8921	8921A	8921AT
TpLH	CL = 30 pF		10	15	15	15	ns
	(Figures 3, 4)
TpHL	CL = 30 pF		10	15	15	15	ns
	(Figures 3, 4)
TTLH	CL = 30 pF		5	8	8	9.5	ns
	(Figures 7, 8)
TTHL	CL = 30 pF		5	8	8	9.5	ns
	(Figures 7, 8)
Skew	CL = 30 pF		1	5	3.5	3.5	ns
	(Figures 3, 4)

Driver Switching Characteristics(Note 6)

DIFFERENTIAL CHARACTERISTICS (Figures 3, 5)

Symbol	Conditions	Min	Typ		Max		Units
				8921	8921A	8921AT
TpLH	CL = 30 pF		10	15	15	15	ns
	(Figures 3, 5, 6)
TpHL	CL = 30 pF		10	15	15	15	ns
	(Figures 3, 5, 6)
|TpLH±T pHL|	CL = 30 pF		0.5	6	2.75	2.75	ns
	(Figures 3, 5, 6)

Note 1: ªAbsolute Maximum Ratingsº are those values beyond which the safety of the device cannot be guaranteed. They are not meant to imply that the device should be operated at these limits. The Table of ªElectrical Characteristicsº provides conditions for actual device operation.

Note 2: All currents into device pins are shown as positive values; all currents out of the device are shown as negative; all voltages are referenced to ground unless otherwise specified. All values shown as max or min are classified on absolute value basis.

Note 3: All typical values are VCC = 5V, TA = 25ÊC.

Note 4: Only one output at a time should be shorted.

Note 5: Difference between complementary outputs at the 50% point.

Note 6: Differential Delays are defined as calculated results from single ended rise and fall time measurements. This approach in establishing AC performance specifications has been taken due to limitations of available Automatic Test Equipment (ATE).

The calculated ATE results assume a linear transition between measurement points and are a result of the following equations:

Where: Tcr = Crossing Point

Tra, Trb, Tfa and T fb are time measurements with respect to the input. See Figure 6 .

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