NSC DS485TN, DS485TMX, DS485TM, DS485N, DS485MX Datasheet

July 1998

DS485

Low Power RS-485/RS-422 Multipoint Transceiver

General Description

The DS485 is a low-power transceiver for RS-485 and RS-422 communication. The device contains one driver and one receiver. The drivers slew rate allows for operation up to 2.5 Mbps (see Applications Information section).

The transceiver draws 200 µA of supply current when unloaded or fully loaded with the driver disabled and operates from a single +5V supply.

The driver is short-circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into TRI-STATE® (High Impedance state) under fault conditions. The driver guarantees a minimum of 1.5V differential output voltage with maximum loading across the common mode range (VOD3).

The receiver has a failsafe feature that guarantees a logic-high output if the input is open circuit.

The DS485 is available in surface mount and DIP packages and is characterized for Industrial and Commercial temperature range operation.

Features

nMeets TIA/EIA RS-485 multipoint standard

nGuaranteed full load output voltage (V OD3)

nLow quiescent current: 200 µA typ

n−7V to +12V common-mode input voltage range

nTRI-STATE outputs on driver and receiver

nAC performance:

ÐDriver transition time: 25 ns typ

ÐDriver propagation delay: 40 ns typ

ÐDriver skew: 1 ns typ

ÐReceiver propagation delay: 200 ns typ

ÐReceiver skew: 20 ns typ

nHalf-duplex flow through pinout

nOperates from a single 5V supply

nAllows up to 32 transceivers on the bus

nCurrent-limiting and thermal shutdown for driver overload protection

nIndustrial temperature range operation

nPin and functional compatible with MAX485 and LTC485

Connection and Logic Diagram

DIP and SOIC

		DS012880-1
Order Number	Temp. Range		Package/###
DS485N	0ÊC to +70ÊC		DIP/N08E
DS485M	0ÊC to +70ÊC		SOP/M08A
DS485TN	−40ÊC to +85ÊC		DIP/N08E
DS485TM	−40ÊC to +85ÊC		SOP/M08A

Truth Table

DRIVER SECTION

RE*	DE	DI		A	B
X	H	H		H	L
X	H	L		L	H
X	L	X		Z	Z
RECEIVER SECTION
RE*	DE		A-B		RO
L	L		³+0.2V		H
L	L		£−0.2V		L
H	X		X		Z
L	L		OPEN*		H

*Note: Non Terminated, Open Input only X = indeterminate

Z = TRI-STATE

TRI-STATE® is a registered trademark of National Semiconductor Corporation.

Transceiver Multipoint 422-485/RS-RS Power Low DS485

© 1999 National Semiconductor Corporation

DS012880

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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 (VCC)	+12V
Enable Input Voltage (RE*, DE)	−0.5V to (V CC + 0.5V)
Driver Input Voltage (DI)	−0.5V to (V CC + 0.5V)
Driver Output Voltage (A, B)	−14V to +14V
Receiver Input Voltage (A, B)	−14V to +14V
Receiver Output Voltage (RO)	−0.5V to (V CC + 0.5V)
Maximum Package Power Dissipation @ +25ÊC
M Package	1.19W
N Package	0.74W
Derate M Package 9.5 mW/ÊC above +25ÊC

Derate N Package 6.0 mW/ÊC above +25ÊC
Maximum Package Power Dissipation @ +70ÊC
M Package	0.76W

N Package	0.47W
Storage Temperature Range	−65ÊC to +150ÊC
Lead Temperature Range
(Soldering, 4 sec.)	+260ÊC
ESD (HBM)	³2 kV

Recommended Operating

Conditions

	Min	Typ	Max	Units
Supply Voltage (VCC)	+4.75	+5.0	+5.25	V
Operating Free Air
Temperature (TA)
DS485	0	+25	+70	ÊC
DS485T	−40	+25	+85	ÊC
Bus Common Mode Voltage	−7		+12	V

Electrical Characteristics

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 2, 3)

Symbol	Parameter		Conditions	Pin	Min	Typ	Max	Units
VOD1	Differential Driver Output Voltage	(No Load)		A, B			5	V
VOD2	Differential Driver Output Voltage	RL = 50W, (RS422), Figure 1			2	2.8		V
	with Load	RL = 27W, (RS485), Figure 1			1.5	2.3	5	V
DVOD	Change in Magnitude of Output	RL = 27W or 50W (Note 4)					0.2	|V|
	Differential Voltage
VOD3	Differential Driver Output Voltage Ð	R1 = 54W, R2 = 375W			1.5	2.0	5	V
	Full Load with Max VCM	VTEST = −7V to +12V, Figure 5
VOC	Driver Common-Mode Output Voltage	RL = 27W or 50W, Figure 1					3	V
DVOC	Change in Magnitude of Common-Mode	RL = 27W or 50W, Figure 1 (Note 4)					0.2	|V|
	Output Voltage
VIH	Input High Voltage			DI,	2.0			V
VIL	Input Low Voltage			DE,			0.8	V
				RE*
IIN1	Input Current	VIN = 0V or VCC					±2	µA
IIN2	Input Current (Note 5)	VIN = +12V		A, B			1.0	mA
	DE = 0V, VCC = 0V or 5.25V	VIN = −7V					−0.8	mA
VTH	Receiver Differential Threshold Voltage	−7V	£ VCM £ +12V		−0.2		0.2	V
DVTH	Receiver Input Hysteresis	VCM = 0V				70		mV
VOH	Receiver Output High Voltage	IO = −4 mA, V ID = 0.2V		RO	3.5			V
VOL	Receiver Output Low Voltage	IO = 4 mA, VID = −0.2V					0.4	V
IOZR	TRI-STATE Output Current at Receiver	0.4V £ VO £ 2.4V					±1	µA
RIN	Receiver Input Resistance	−7V	£ VIN £ +12V	A, B	12			kW
ICC	No-Load Supply Current (Note 6)	DE = VCC, RE* = 0V or VCC		VCC		200	900	µA
		DE = 0V, RE* = 0V or VCC				200	500	µA
IOSD1	Driver Short Circuit Current, VO = HIGH	−7V	£ VO £ +12V	A, B	35		250	mA
IOSD2	Driver Short Circuit Current, VO = LOW	−7V	£ VO £ +12V		35		250	mA
IOSR	Receiver Short Circuit Current	0V £ VO £ VCC		RO	7		85	mA

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Switching Characteristics

Over Supply Voltage and Operating Temperature Ranges, unless otherwise specified (Notes 3, 7, 8)

Symbol	Parameter	Conditions	Min	Typ	Max	Units
tPLHD	Driver Differential Propagation Delay Ð Low to High	R L = 54Ω, CL = 100 pF	10	40	65	ns
tPHLD	Driver Differential Propagation Delay Ð High to Low		10	39	65	ns
tSKEW	Differential Skew |tPHLD − t PLHD|			1	10	ns
tr	Driver Rise Time		3	25	40	ns
tf	Driver Fall Time		3	25	40	ns
tZH	Driver Enable to Output High	CL = 100 pF			170	ns
tZL	Driver Enable to Output Low	CL = 100 pF			170	ns
tLZ	Driver Disable from Output Low	CL = 15 pF			170	ns
tHZ	Driver Disable from Output High	CL = 15 pF			170	ns
tPLHD	Receiver Differential Propagation Delay Ð Low to High	C L = 15 pF (RO)	70	190	320	ns
tPHLD	Receiver Differential Propagation Delay Ð High to Low		70	210	320	ns
tSKEW	Differential Skew |tPHLD − t PLHD|			20	50	ns
tZH	Receiver Enable to Output High	CL = 15 pF			110	ns
tZL	Receiver Enable to Output Low				110	ns
tLZ	Receiver Disable from Output Low				110	ns
tHZ	Receiver Disable from Output High				110	ns
fmax	Maximum Data Rate	(Note 9)	2.5			Mbps

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 devices should be operated at these limits. The table of ªElectrical Characteristicsº specifies conditions of device operation.

Note 2: Current into device pins is defined as positive. Current out of device pins is defined as negative. All voltages are referenced to ground except VOD1/2/3 and VID.

Note 3: All typicals are given for: VCC = +5.0V, TA = +25ÊC.

Note 4: |VOD| and |VOC| are changes in magnitude of V OD and VOCrespectively, that occur when the input changes state.

Note 5: IIN2 includes the receiver input current and driver TRI-STATE leakage current.

Note 6: Supply current specification is valid for loaded transmitters when DE = 0V or enabled (DE = H) with no load. Note 7: f = 1 MHz, tr and tf ≤ 6 ns, ZO = 50Ω.

Note 8: CL includes jig and probe capacitance.

Note 9: fmax is the guaranteed data rate for 50 ft of twisted pair cable. f max may be conservatively determined from the ratio of driver transition time (tr) to the data rate unit interval (1/fmax). Using a 10% ratio yields fmax = (0.1)/40 ns = 2.5 Mb/s. Higher data rates may be supported by allowing larger ratios.

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