ST ST3485EB, ST3485EC User Manual

ST3485EB

ST3485EC

3.3 V powered, 15 kV ESD protected, up to 12 Mbps RS-485/RS-422 transceiver

Features

■ESD protection

–±15 kV human body model

–±8 kV IEC 1000-4-2 contact discharge

■Operate from a single 3.3 V supply - no charge pump required

■Interoperable with 5 V logic

■1 µA low current shutdown mode max

■Guaranteed 12 Mbps data rate

■-7 to 12 V common mode input voltage range

■Half duplex versions available

■Industry standard 75176 pinout

■Current limiting and thermal shutdown for driver overload protection

■Guaranteed high receiver output state for floating inputs with no signal present

■Allow up to 64 transceivers on the bus

DIP-8

SO-8

Driver is short-circuit current limited and is protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state.

Description

The ST3485E is ±15 kV ESD protected, 3.3 V low power transceiver for RS-485 and RS-422 communications. The device contains one driver and one receiver in half duplex configuration. The ST3485E transmits and receives at a guaranteed data rate of at least 12 Mbps.

All transmitter outputs and receiver inputs are protected to ±15 kV using Human Body Model.

Table 1.	Device summary
Order code		Temperature range	Package	Packaging
ST3485ECN		0 to 70 °C	DIP-8	50 parts per tube / 40 tube per box
ST3485ECDR		0 to 70 °C	SO-8 (tape and reel)	2500 parts per reel
ST3485EBDR		-40 to 85 °C	SO-8 (tape and reel)	2500 parts per reel
November 2007			Rev 5	1/22

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Contents	ST3485EB - ST3485EC

Contents

1	Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 3
2	Truth tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	. 4
3	Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	5
4	Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
5	Test circuits and typical characteristics . . . . . . . . . . . . . . . . . . . . . . . . .	9
6	Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	17
7	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	21

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ST3485EB - ST3485EC	Pin configuration

1 Pin configuration

Figure 1. Pin connections

Table 2.	Pin description
Pin n°	Symbol			Name and function
1	RO			Receiver output. If A>B by 200mV, RO will be high; if A<B by 200mV, RO will be low
				Receiver output enable. RO is enabled when RE is low; RO is high impedance when RE
2		RE
				is high. If RE is high and DE is low, the device will enter a low power shutdown mode.
				Driver output enable. The driver outputs are enabled by bringing DE high. They are high
3		DE		impedance when DE is low. If RE is high DE is low, the device will enter a low-power
				shutdown mode. If the driver outputs are enabled, the part functions as line driver, while
				they are high impedance, it functions as line receivers if RE is low.
4		DI		Driver input. A low on DI forces output A low and output B high. Similarly, a high on DI
				forces output A high and output B low
5	GND			Ground
6		A		Non-inverting receiver input and non-inverting driver output
7		B		Inverting receiver input and inverting driver output
8	VCC			Supply voltage: VCC= 3V to 3.6V

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Truth tables								ST3485EB - ST3485EC
2	Truth tables
Table 3.	Truth table (driver)
		Inputs				Outputs		Mode
RE		DE		DI	B		A
X		H		H	L		H	Normal
X		H		L	H		L	Normal
L		L		X	Z		Z	Normal
H		L		X	Z		Z	Shutdown

	Note:	X= Don’t care; Z=High impedance
	Table 4.	Truth table (receiver)
			Inputs	Output	Mode
	RE	DE	A-B	RO
	L	L	≥ 0.2V	H	Normal
	L	L	≤-0.2V	L	Normal
	L	L	Inputs Open	H	Normal
	H	L	X	Z	Shutdown
	Note:	X= Don’t care; Z=High impedance

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ST3485EB - ST3485EC

Maximum ratings

3

Maximum ratings

Table 5.

Absolute maximum ratings

Symbol

Parameter

Value

Unit

VCC

Supply voltage

7

V

VI

Control input voltage

DE)

-0.3 to 7

V

(RE,

VDI

Driver input voltage (DI)

-0.3 to 7

V

VDO

Driver output voltage (A, B)

± 14

V

VRI

Receiver input voltage (A, B)

± 14

V

VRO

Receiver output voltage (RO)

-0.3 to (VCC + 0.3)

V

Note:

Absolute maximum ratings are those values beyond which damage to the device may occur.

Functional operation under these condition is not implied.

Table 6.

ESD performance: transmitter outputs, receiver inputs

Symbol

Parameter

Test conditions

Min.

Typ.

Max.

Unit

ESD

ESD protection voltage

Human body model

± 15

kV

ESD

ESD protection voltage

IEC-1000-4-2 Contact discharge

± 8

kV

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Electrical characteristics	ST3485EB - ST3485EC

4 Electrical characteristics

Table 7. Electrical characteristics

VCC = 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred to TA = 25 °C)

Symbol	Parameter	Test conditions				Min.	Typ.	Max.	Unit
				DE=VCC,			1.3	2.2	mA
ISUPPLY	VCC Power supply current	No Load, DI=0V or VCC		RE=0V or VCC
				DE=0V,			1.2	1.9	mA
				RE=0V
ISHDN	Shutdown supply current	DE=0V, RE=VCC, DI=0V or VCC					0.002	1	µA

Table 8. Logic input electrical characteristics

VCC = 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred to TA = 25 °C)

Symbol	Parameter	Test conditions		Min.	Typ.	Max.	Unit
VIL	Input logic threshold low	DE, DI, RE			1.3	0.8	V
VIH	Input logic threshold high	DE, DI, RE		2			V
IIN1	Logic input current	DE, DI, RE				± 2.0	µA
IIN2	Input current (A, B)	DE=0V, VCC= 0 or 3.6V	VIN=12V			1	mA
			VIN=-7V			-0.8	mA

Table 9. Transmitter electrical characteristics

VCC = 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred to TA = 25°C)

Symbol	Parameter	Test conditions	Min.	Typ.	Max.	Unit
		RL= 100Ω (RS-422) (Figure 1)	2			V
VOD	Differential drive output	RL= 54Ω (RS-485) (Figure 1)	1.5			V
		RL= 60Ω (RS-485) (Figure 2)	1.5			V
	Change in magnitude of driver
VOD	differential output voltage for	RL= 54Ω or 100Ω (Figure 1)			0.2	V
	complementary output states
	(Note: 1)
VOC	Driver common mode output	RL= 54Ω or 100Ω (Figure 1)			3	V
	voltage
	Change in magnitude of driver	RL= 54Ω or 100Ω (Figure 1)
VOC	common mode output voltage				0.2	V
	(Note: 1)
IOSD	Driver short circuit output				± 250	mA
	current

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ST3485EB - ST3485EC	Electrical characteristics

Table 10. Receiver electrical characteristics

VCC = 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred to TA = 25°C)

Symbol	Parameter	Test conditions	Min.	Typ.	Max.	Unit
VTH	Receiver differential	VCM = -7V to 12V, DE = 0	-0.2		0.2	V
	threshold voltage
VTH	Receiver input hysteresis	VCM = 0V		70		V
VOH	Receiver output high	IOUT = -4mA, VID = 200mV	2			V
	voltage	(Figure 8 and Figure 9)
VOL	Receiver output low	IOUT = 4mA, VID = -200mV, (Figure 3)			0.4	V
	voltage
IOZR	3-State (high impedance)	VCC = 3.6V, VO = 0V to VCC			± 1	µA
	output current at receiver
RRIN	Receiver input resistance	VCM = -7V to 12V	24			kΩ
IOSR	Receiver short-circuit	VRO = 0V to VCC	7		60	mA
	current

Table 11. Driver switching characteristics

VCC = 3 V to 3.6 V, TA = -40 to 85 °C, unless otherwise specified. Typical values are referred to TA = 25 °C)

Symbol	Parameter	Test conditions	Min.	Typ.	Max.	Unit
DR	Maximum data rate		12	15		Mbps
tDD	Differential output delay	RL= 60Ω, CL = 15pF, (Figure 4 and		18	30	ns
		Figure 5)
tTD	Differential output	RL= 60Ω, CL = 15pF, (Figure 4 and		12	20	ns
	transition time	Figure 5)
tPLH	Propagation delay	RL= 27Ω, CL = 15pF, (Figure 8 and		18	30	ns
tPHL		Figure 9)
tPDS	|tPLH - tPHL| Propagation	RL= 27Ω, CL = 15pF, (Figure 8 and		2	5	ns
	delay skew (Note 2)	Figure 9)
tPZL	Output enable time	RL= 110Ω, (Figure 10 and Figure 11)		19	35	ns
tPZH	Output enable time	RL= 110Ω, (Figure 6 and Figure 7)		30	50	ns
tPHZ	Output disable time	RL= 110Ω, (Figure 6 and Figure 7)		19	35	ns
tPLZ	Output disable time	RL= 110Ω, (Figure 10 and Figure 11)		30	50	ns
tSKEW	Differential output delay			1	3	ns
	skew
tZH(SHDN)	Driver enable from			30	50	ns
	shutdown to output high
tZL(SHDN)	Driver enable from			19	35	ns
	shutdown to output low

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