MAXIM MAX3097E, MAX3098E User Manual

General Description

The MAX3097E/MAX3098E feature three high-speed RS485/RS-422 receivers with fault-detection circuitry and fault-status outputs. The receivers’ inputs have fault thresholds that detect when the part is not in a valid state.

The MAX3097E/MAX3098E indicate when a receiver input is in an open-circuit condition, short-circuit condition, or outside the common-mode range. They also generate a fault indication when the differential input voltage goes below a preset threshold. See Ordering Information or the Electrical Characteristics for threshold values.

The fault circuitry includes a capacitor-programmable delay to ensure that there are no erroneous fault conditions even at slow edge rates. Each receiver is capable of accepting data at rates up to 32Mbps.

________________________Applications

RS-485/RS-422 Receivers for Motor-Shaft Encoders

High-Speed, Triple RS-485/RS-422 Receiver with Extended Electrostatic Discharge (ESD)

Triple RS-485/RS-422 Receiver with Input Fault Indication

Telecommunications

Embedded Systems

Features

♦ Detects the Following RS-485 Faults:

Open-Circuit Condition Short-Circuit Condition Low Differential Voltage Signal Common-Mode Range Violation

♦ ESD Protection

±15kV—Human Body Model ±15kV—IEC 1000-4-2, Air-Gap Discharge Method ±8kV—IEC 1000-4-2, Contact Discharge Method

♦ Single +3V to +5.5V Operation

♦ -10V to +13.2V Extended Common-Mode Range

♦ Capacitor-Programmable Delay of Fault Indication

Allows Error-Free Operation at Slow Data Rates

♦ Independent and Universal Fault Outputs

♦ 32Mbps Data Rate

♦ 16-Pin QSOP is 40% Smaller than Industry-

Standard 26LS31/32 Solutions

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

________________________________________________________________ Maxim Integrated Products 1

Pin Configuration

ENCODED SIGNALS

A, A, B, B, Z, Z

MOTOR DRIVER

MOTOR

MOTOR CONTROLLER

ALARM OUTPUTS

RECEIVER OUTPUTS

DSP

MAX3097E MAX3098E

MAX547

12-BIT D/A

Typical Application Circuit

19-1727; Rev 0; 7/00

For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800. For small orders, phone 1-800-835-8769.

Ordering Information

Ordering Information continued at end of data sheet.

PART TEMP. RANGE

MAX3097ECEE 0°C to +70°C 16 QSOP

MAX3097ECSE 0°C to +70°C 16 SO

PINPACKAGE

TOP VIEW

GND

DELAY

QSOP/SO/DIP

MAX3097E MAX3098E

ALARMA

OUTA

ALARMB

OUTB

ALARMZ

OUTZ

ALARMD

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(VCC= +3V to +5.5V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V and TA = +25°C.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Supply Voltage (VCC).............................................................+7V

Receiver Input Voltage (A, A, B, B, Z, Z) .............................±25V

Output Voltage (OUT_, ALARM_)...............-0.3V to (V

+ 0.3V)

DELAY ........................................................-0.3V to (V

+ 0.3V)

Continuous Power Dissipation (T

= +70°C)

16-Pin QSOP (derate 8.3mW/°C above +70°C)............667mW

16-Pin SO (derate 8.7mW/°C above +70°C).................696mW

16-Pin Plastic DIP (derate 10.53mW/°C

above +70°C).............................................................762mW

Operating Temperature Ranges

MAX3097EC_E...................................................0°C to +70°C

MAX3098E_C_E.................................................0°C to +70°C

MAX3097E_E_E ..............................................-40°C to +85°C

MAX3098E_E_E ..............................................-40°C to +85°C

Storage Temperature Range .............................-65°C to +150°C

Junction Temperature......................................................+150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

Supply Voltage Range V

Supply Current I

Receiver Differential Threshold Voltage (Note 1)

Receiver Input Hysteresis ∆V

Output High Voltage V

Output Low Voltage V

Receiver Input Resistance R

Input Current (A , A , B , B (Z , Z )

Output Short-Circuit Current I

FAULT DETECTION

MAX3097E Fault-Detection Receiver Differential Threshold Voltage (Note 3)

MAX3098EA Fault-Detection Receiver Differential Threshold Voltage (Note 3)

No load 3.1 4.0 mA

-10V ≤ VCM ≤ 13.2V -200 +200 mV

-10V ≤ VCM ≤ 13.2V 40 mV

VCC = 4.75V, IO = -4mA, VID = 200mV V

VCC = 3.0V, IO = -1mA, VID = 200mV VCC - 1.0

VCC = 4.75V, IO = +4mA, VID = -200mV 0.4

VCC = 3.0V, IO = +1mA, VID = -200mV 0.4

-10V ≤ V

≤ 13.2V 90 160 kΩ

VCC = 0 or 5.5V

≤ V

0 ≤ V

OSR

DIFH

VCM = 0

DIFL

DIFH

VCM = 0

DIFL

3 5.5 V

- 1.5

= 13.2V

(Note 2)

= -10V

(Note 2)

0.07 0.14

-0.05 -0.11

±105 mA

High limit 275 475

Low limit -475 -275

High limit 0.12 0.20

Low limit -0.20 -0.12

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= +3V to +5.5V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V and TA = +25°C.)

SWITCHING CHARACTERISTICS

(VCC= +3V to +5.5V, VID= ±3.0V, TA= T

MIN

to T

MAX

, unless otherwise noted. Typical values are at VCC= +5V and TA = +25°C.)

Note 1: VCMis the common-mode input voltage. VIDis the differential input voltage. Note 2: V

is the input voltage at pins A, A, B, B, Z, Z.

Note 3: A differential terminating resistor is required for proper function of open-circuit fault detection (see Applications Information). Note 4: See Applications Information for a discussion of the receiver common-mode voltage range and the operating conditions for

fault indication.

Note 5: Applies to the individual channel immediate-fault outputs (ALARM_) and the general delayed-fault output (ALARMD) when

there is no external capacitor at DELAY.

Note 6: Equivalent pulse test: 1.3V / (t

DFLH

- t

DFHL

) ≥ SRD.

Note 7: Equivalent pulse test: 0.62V / (t

DFLH

- t

DFHL

) ≥ SRD.

MAX3098EB Fault-Detection Receiver Differential Threshold Voltage (Note 3)

Fault-Detection Common-Mode Voltage Range (Note 4)

DELAY Current Source VCC = 5V, V

DELAY Threshold

ESD PROTECTION

ESD Protection (A, A, B, B, Z, Z)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

DIFH

DIFL

CMH

CML

VCM = 0

High limit 13.2

Low limit -10

= 0 9 10 11 µA

DELAY

VCC = 3V 1.55 1.73 1.90

= 5V 3.1 3.29 3.5

Human Body Model ±15

IEC1000-4-2 (Air-Gap Discharge) ±15

IEC1000-4-2 (Contact Discharge)

Propagation Delay from Input to Output

Receiver Skew |t

Channel-to-Channel Propagation Delay Skew

Maximum Data Rate f

FAULT DETECTION

Differential Fault Propagation Delay to Output (Note 5)

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

PLH

- t

PLH

PHL

, t

SKEW

MAX

DFLH

DFHL

PHL

CL = 15pF, Figures 1, 2

CL = 15pF, Figures 1, 2 ±10 ns

= 15pF, Figures 1, 2 ±10 ns

CL = 15pF, Figure 1 32 Mbps

CLF = 15pF, Figures 1, 3

High limit 70 250

Low limit -250 -70

±8

VCC = 4.5V to 5.5V 75

= 3.0V to 3.6V 85

1.2

µs

Minimum Differential Slew Rate to Avoid False Alarm Output

Common-Mode Fault Propagation Delay to Output (Note 5)

CMFLH

CMFHL

MAX3097E (Note 6) 1.0

MAX3098E (Note 7) 0.33

CL = 15pF, Figures 1, 4

V/µs

µs

1.5

DELAYED ALARM OUTPUT

MAX3097E/8E toc06

20µs/div

CH 1

CH 2

CH 3

GND

CH1: VA, 5V/div CH2: V

ALARMA

, 5V/div

CH3: V

ALARMD

, 5V/div

A =

GND, C

DELAY

= 270pF

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

4 _______________________________________________________________________________________

Typical Operating Characteristics

(Typical values are at VCC= +5V and TA= +25°C.)

100

1000

10,000

10010 1000

10,000

ALARMD OUTPUT DELAY

vs. CAPACITANCE

MAX3097E/8Etoc01

CAPACITANCE (pF)

ALARMD OUTPUT DELAY (µs)

VCC = 5V

VCC = 3V

-40 0-20

40 60

RECEIVER PROPAGATION DELAY

vs. TEMPERATURE

MAX3097E/8E toc02

TEMPERATURE (°C)

RECEIVER PROPAGATION DELAY (ns)

VCC = 5.0V

VCC = 3.3V

SUPPLY CURRENT vs.

TEMPERATURE

MAX3097E/8E toc03

SUPPLY CURRENT (mA)

-40 0-20

40 60

TEMPERATURE (°C)

VCC = 5.0V

VCC = 3.3V

NO LOAD

0.5

1.0

1.5

2.0

2.5

3.5

3.0

4.5

4.0

5.0

-45 -35-40 -30 -25 -20 -15 -10 -5 0

RECEIVER OUTPUT LOW VOLTAGE

vs. OUTPUT CURRENT

MAX3097E/8E toc04

OUTPUT CURRENT (mA)

OUTPUT LOW VOLTAGE (V)

VCC = 5.0V

VCC = 3.3V

010515203025

RECEIVER OUTPUT HIGH VOLTAGE

vs. OUTPUT CURRENT

MAX3097E/8E toc05

OUTPUT CURRENT (mA)

OUTPUT HIGH VOLTAGE (V)

VCC = 5.0V

VCC = 3.3V

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

_______________________________________________________________________________________ 5

Typical Operating Characteristics (continued)

(Typical values are at VCC= +5V and TA= +25°C.)

MAX3097E

LOW DIFFERENTIAL INPUT FAULT

MAX3097E/8E toc08

CH 2 GND

GND

CH 1

100µs/div

CH1: V

, 200mV/div

CH2: V

ALARMA

, 5V/div

A =

GND

SLEW-RATE FAULT

MAX3097E/8E toc09

CH 2 GND

GND

CH 1

CH1: V

, 5V/div

CH2: V

ALARMA

, 5V/div SLEW RATE = 0.05V/µs V

A =

GND

-8

-4

-10 0-5 5 10

FAULT-DETECTION RECEIVER DIFFERENTIAL

THRESHOLD VOLTAGE SHIFT vs.

COMMON-MODE VOLTAGE

MAX3097E/8E toc10

COMMON-MODE VOLTAGE (V)

THRESHOLD SHIFT (mV)

MAX3097E

MAX3098E

COMMON-MODE VOLTAGE FAULT

(HIGH SIDE)

COMMON-MODE VOLTAGE FAULT

(LOW SIDE)

CH 1

CH 2

CH 3

CH1: VA + AC(60Hz), 10V/div CH2: V

OUTA

CH3: V

ALARMA

CC =

, 5V/div

2ms/div

MAX3097E/8E toc07a

GND

CH 1

CH 2

CH 3

CH1: V CH2: V CH3: V V

CC =

A OUTA ALARMA

, 5V/div

2ms/div

+ AC(60Hz), 10V/div

MAX3097E/8E toc07b

GND

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

6 _______________________________________________________________________________________

Pin Description

PIN NAME FUNCTION

1 A Noninverting Receiver A Input

2 A Inverting Receiver A Input

3 B Noninverting Receiver B Input

4 B Inverting Receiver B Input

5 Z Noninverting Receiver Z Input

6 Z Inverting Receiver Z Input

7 GND Ground

Programmable Delay Terminal. Connect a capacitor from DELAY to GND to set the

8 DELAY

9 ALARMD

ALARMD output delay time. To obtain a minimum delay, leave DELAY unconnected. See Capacitance vs. ALARMD Output Delay in the Typical Operating Characteristics.

Delayed Fault Output. This output is the logic OR of ALARMA, ALARMB, and ALARMZ. Place a capacitor from the DELAY pin to GND to set the delay (see Setting Delay Time). A high logic level indicates a fault condition on at least one receiver input pair. A low level on this pin indicates no fault condition is present.

Z Receiver Output. If V

10 OUTZ

11 ALARMZ

be low. If Z or Z exceeds the receiver’s input common-mode voltage range, the ALARMZ output will be high and OUTZ will be indeterminate.

Z Fault Output. When ALARMZ is high, OUTZ is indeterminate. Tables 1 and 2 show all the possible states for which an alarm is set.

- V Z ≥ +200mV, OUTZ will be high. If VZ - V Z ≤ -200mV, OUTZ will

B Receiver Output. If V

12 OUTB

13 ALARMB

14 OUTA

15 ALARMA

16 V

be low. If B or B exceeds the input receiver’s common-mode voltage range, the ALARMB output will be high and OUTB will be indeterminate.

B Fault Output. When ALARMB is high, OUTB is indeterminate. Tables 1 and 2 show all the possible states for which an alarm is set.

A Receiver Output. If V be low. If A or A exceeds the receiver’s input common-mode voltage range, the ALARMA output will be high and OUTA will be indeterminate.

A Fault Output. When ALARMA is high, OUTA is indeterminate. Tables 1 and 2 show all the possible states for which an alarm is set.

Power Supply

- V B ≥ +200mV, OUTB will be high. If VB - V B ≤ -200mV, OUTB will

- V A ≥ +200mV, OUTA will be high. If VA - V A ≤ -200mV, OUTA will

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

_______________________________________________________________________________________ 7

Figure 1. Typical Receiver Test Circuit

Figure 2. Propagation Delay

Figure 3. Fault-Detection Timing

Figure 4. Common-Mode Fault Propagation Delay

Test Circuits and Waveforms

Detailed Description

The MAX3097E/MAX3098E feature high-speed, triple RS-485/RS-422 receivers with fault-detection circuitry and fault-status outputs. The fault outputs are active push-pull, requiring no pull-up resistors. The fault circuitry includes a capacitor-programmable delayed FAULT_ output to ensure that there are no erroneous fault conditions even at slow edge rates (see Delayed Fault Output). The receivers operate at data rates up to 32Mbps.

The MAX3097E/MAX3098E are designed for motorshaft encoders with standard A, B, and Z outputs (see

Using the MAX3097E/MAX3098E as Shaft Encoder Receivers). The devices provide an alarm for open-cir-

cuit conditions, short-circuit conditions, data nearing the minimum differential threshold conditions, data below the minimum threshold conditions, and receiver inputs outside the input common-mode range. Tables 1 and 2 are functional tables for each receiver.

ALARMA

(FAULT OUTPUT)

OR ALARMD

OUTA

+3V

-3V

OV OV

PLH

RISE/FALL TIMES ≤2ns

PHL

/2VCC/2

DIFH

-3.0V

ALARM OR ALARMD

DIFL

DFLH

DFHL

CMH

+3.0V

VCC/2VCC/2

CML

CMFLH

ALARM OR ALARMD

VCC/2

CMFHL

CMFLH

CMFHL

VCC/2

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

8 _______________________________________________________________________________________

Note 1: ALARMD indicates fault for any receiver. Note 2: Receiver output may oscillate with this differential input condition. Note 3: See Applications Information for conditions leading to input range fault condition.

X = Don’t care

Table 1. MAX3097E Alarm Function Table (Each Receiver)

Table 2. MAX3098EA Alarm Function Table (Each Receiver)

X = Don’t care; for B-grade functionality, replace V

input values in Table 2 with B-grade parameters from Electrical Characteristics.

(DIFFERENTIAL

INPUT VOLTAGE)

≥0.475V 1 0 0 Normal Operation

<0.475V and ≥0.275V 1 Indeterminate Indeterminate Indeterminate

<0.275V and ≥0.2V 1 1 1 Low Input Differential Voltage

≤0.2V and ≥-0.2V

≤-0.2V and >-0.275V 0 1 1 Low Input Differential Voltage

≤-0.275V and

>-0.475V

≤-0.475V

INPUTS OUTPUTS

X <-10V or >+13.2V

COMMON-MODE

VOLTAGE

≤13.2V and ≥-10V

OUT_ ALARM_

Indeterminate

(Note 2)

0 Indeterminate Indeterminate

000

Indeterminate

(Note 3)

ALARMD

t ≥ DELAY

(NOTE 1)

1 1 Low Input Differential Voltage

FAULT CONDITION

Indeterminate

Outside Common-Mode

Voltage Range

(DIFFERENTIAL

INPUT VOLTAGE)

≥0.2V 1 0 0 Normal Operation

<0.2V and ≥0.12V

<0.12V and ≥ - 0.12V

≤-0.12V and ≥ -0.2V

≤-0.2V

INPUTS OUTPUTS

COMMON-MODE

VOLTAGE

≤13.2V and ≥-

10V

<-10V or >+13.2V

OUT_ ALARM_

Indeterminate

(Note 2)

Indeterminate

0 0 0 Normal Operation

Indeterminate

(Note 3)

ALARMD

t ≥ DELAY

(NOTE 1)

Indeterminate Indeterminate Indeterminate

1 1 Low Input Differential Voltage

Indeterminate Indeterminate Indeterminate

FAULT CONDITION

Outside Common-Mode Voltage

Range

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

_______________________________________________________________________________________ 9

±15kV ESD Protection

As with all Maxim devices, ESD-protection structures are incorporated on all pins to protect against ESD encountered during handling and assembly. The MAX3097E/MAX3098E receiver inputs have extra protection against static electricity found in normal operation. Maxim’s engineers developed state-of-the-art structures to protect these pins against ±15kV ESD without damage. After an ESD event, the MAX3097E/ MAX3098E continue working without latchup.

ESD protection can be tested in several ways. The receiver inputs are characterized for protection to the following:

• ±15kV using the Human Body Model

• ±8kV using the Contact Discharge method specified

in IEC 1000-4-2 (formerly IEC 801-2)

• 15kV using the Air-Gap Discharge method specified in IEC 1000-4-2 (formerly IEC 801-2)

ESD Test Conditions

ESD performance depends on a number of conditions. Contact Maxim for a reliability report that documents test setup, methodology, and results.

Human Body Model

Figure 5a shows the Human Body Model, and Figure 5b shows the current waveform it generates when discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest, which is then discharged into the device through a

1.5kΩ resistor.

IEC 1000-4-2

Since January 1996, all equipment manufactured and/or sold in the European community has been required to meet the stringent IEC 1000-4-2 specification. The IEC 1000-4-2 standard covers ESD testing and performance of finished equipment; it does not specifically refer to integrated circuits. The MAX3097E/MAX3098E help you design equipment that meets Level 4 (the highest level) of IEC 1000-4-2, without additional ESD-protection components.

The main difference between tests done using the Human Body Model and IEC 1000-4-2 is higher peak current in IEC 1000-4-2. Because series resistance is lower in the IEC 1000-4-2 ESD test model (Figure 6a), the ESD-withstand voltage measured to this standard is generally lower than that measured using the Human Body Model. Figure 6b shows the current waveform for the ±8kV IEC 1000-4-2 Level 4 ESD Contact Discharge test. The Air-Gap test involves approaching the device with a charge probe. The Contact Discharge method connects the probe to the device before the probe is energized.

Machine Model

The Machine Model for ESD testing uses a 200pF storage capacitor and zero-discharge resistance. It mimics the stress caused by handling during manufacturing and assembly. All pins (not just RS-485 inputs) require this protection during manufacturing. Therefore, the Machine Model is less relevant to the I/O ports than are the Human Body Model and IEC 1000-4-2.

Figure 5a. Human Body ESD Test Model

Figure 5b. Human Body Model Current Waveform

1MΩ

CHARGE-CURRENT

LIMIT RESISTOR

HIGH-

VOLTAGE

SOURCE

100pF

1.5k

DISCHARGE

RESISTANCE

STORAGE CAPACITOR

DEVICE UNDER

TEST

IP 100%

90%

AMPERES

36.8%

10%

TIME

CURRENT WAVEFORM

PEAK-TO-PEAK RINGING

(NOT DRAWN TO SCALE)

___________Applications Information

Using the MAX3097E/MAX3098E as Shaft

Encoder Receivers

The MAX3097E/MAX3098E are triple RS-485 receivers designed for shaft encoder receiver applications. A shaft encoder is an electromechanical transducer that converts mechanical rotary motion into three RS-485 differential signals. Two signals, A (A and A) and B (B and B) provide incremental pulses as the shaft turns, while the index signal, Z (Z and Z) occurs only once per revolution to allow synchronization of the shaft to a known position. Digital signal processing (DSP) techniques are used to count the pulses and provide feedback of both shaft position and shaft velocity for a stable positioning system.

Shaft encoders typically transmit RS-485 signals over twisted-pair cables since the signal often has to travel across a noisy electrical environment (Figure 7).

Detecting Faults

Signal integrity from the shaft encoder to the DSP is essential for reliable system operation. Degraded signals could cause problems ranging from simple miscounts to loss of position. In an industrial environment, many problems can occur within the three twisted pairs. The MAX3097E/MAX3098E can detect various types of common faults, including a low-input-level signal, open-circuit wires, short-circuit wires, and an input signal outside the common-mode input voltage range of the receiver.

Detecting Short Circuits

In Figure 8, if wires A and A are shorted together, then A and A will be at the same potential, so the difference in the voltage between the two will be approximately 0. This causes fault A to trigger since the difference between A A is less than the differential fault threshold.

Detecting Open-Circuit Conditions

Detecting an open-circuit condition is similar to detecting a short-circuit condition and relies on the terminating resistor being across A and A. For example, if the wire drops out of the A terminal, A pulls A through the terminating resistor to look like the same signal. In this condition, VIDis approximately 0 and a fault occurs.

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

10 ______________________________________________________________________________________

Figure 7. Typical Shaft Encoder Output

Figure 6a. IEC 1000-4-2 ESD Test Model

Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform

50MΩ to 100MΩ

CHARGE-CURRENT

LIMIT RESISTOR

HIGH-

VOLTAGE

SOURCE

100%

90%

PEAK

10%

tr = 0.7ns to 1ns

150pF

30ns

330Ω

DISCHARGE

RESISTANCE

STORAGE CAPACITOR

60ns

DEVICE UNDER

TEST

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

______________________________________________________________________________________ 11

Common-Mode Range

The MAX3097E/MAX3098E contain circuitry that detects if the input stage is going outside its useful common-mode range. If the received data could be unreliable, a fault signal is triggered.

Detecting Low Input Differential

Due to cable attenuation on long wire runs, it is possible that VID< 200mV, and incorrect data will be received. In this condition, a fault will be indicated.

Delayed Fault Output

The delayed fault output provides a programmable blanking delay to allow transient faults to occur without triggering an alarm. Such faults may occur with slow signals triggering the receiver alarm through the zero crossover region.

Figure 9 shows the delayed alarm output.

ALARMD performs a logic OR of ALARMA, ALARMB, and ALARMZ (Figure 10). A NOR gate drives an Nchannel MOSFET so that in normal operation with no faults, the current source (10µA typ) is shunted to

ground. Upon activation of any alarm from receiver A, B, or Z, the MOSFET is turned off, allowing the current source to charge C

DELAY

. When V

DELAY

exceeds the DELAY threshold, the comparator output, ALARMD, goes high. ALARMD is reset when all receiver alarms go low, quickly discharging C

DELAY

to ground.

Setting Delay Time

ALARMD’s delay time is set with a single capacitor connected from DELAY to GND. The delay comparator threshold varies with supply voltage, and the C

DELAY

value can be determined for a given time delay period from the Capacitance vs. ALARMD Output Delay graph in the Typical Operating Characteristics or using the following equations:

tD= 15 + 0.33 x C

DELAY

(for VCC= 5V)

and

tD= 10 + 0.187 x C

DELAY

(for VCC= 3V)

where tDis in µs and C

DELAY

is in pF.

Figure 9. Delayed Alarm Output

Figure 10. ALARMD Simplified Schematic

Figure 8. Short-Circuit Detection

NORMAL OPERATION SHORT CIRCUIT A TO A

ALARMA

ALARMB

ALARMD

DELAY CURRENT SOURCE

ALARMA ALARMB

ALARMZ

ALARM_

DELAY

ALARMD

*The capacitor (C If the duration of an ALARM_ pulse is less than t output will be present at ALARMD.

NMOS

) charges up slowly, but discharges rapidly.

DELAY

(EXTERNAL)

DLY

DELAY COMPARATOR

ALARMD

DELAY THRESHOLD

, no alarm

DLY

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

12 ______________________________________________________________________________________

Functional Diagram

Chip Information

TRANSISTOR COUNT: 675

PROCESS: CMOS

Ordering Information (continued)

PART

TEMP. RANGE

PINPACKAGE

MAX3097ECPE 0°C to +70°C 16 Plastic DIP

MAX3097EEEE -40°C to +85°C 16 QSOP

MAX3097EESE -40°C to +85°C 16 SO

MAX3097EEPE -40°C to +85°C 16 Plastic DIP

MAX3098EACEE 0°C to +70°C 16 QSOP

MAX3098EACSE 0°C to +70°C 16 SO

MAX3098EACPE 0°C to +70°C 16 Plastic DIP

MAX3098EAEEE -40°C to +85°C 16 QSOP

MAX3098EAESE -40°C to +85°C 16 SO

MAX3098EAEPE -40°C to +85°C 16 Plastic DIP

MAX3098EBCEE 0°C to +70°C 16 QSOP

MAX3098EBCSE 0°C to +70°C 16 SO

MAX3098EBCPE 0°C to +70°C 16 Plastic DIP

MAX3098EBEEE -40°C to +85°C 16 QSOP

MAX3098EBESE -40°C to +85°C 16 SO

MAX3098EBEPE

-40°C to +85°C 16 Plastic DIP

MAX3097E MAX3098E

ALARMA

OUTA

ALARMB

OUTB

ALARMZ

OUTZ

ALARMD

DELAY

GND

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

______________________________________________________________________________________ 13

Package Information

SOICN.EPS

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

14 ______________________________________________________________________________________

Package Information (continued)

QSOP.EPS

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V,

Triple RS-422/RS-485 Receivers with Fault Detection

______________________________________________________________________________________ 15

Package Information (continued)

PDIPN.EPS

MAX3097E/MAX3098E

±15kV ESD-Protected, 32Mbps, 3V/5V, Triple RS-422/RS-485 Receivers with Fault Detection

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.

16 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

NOTES

MAXIM MAX3097E, MAX3098E User Manual

Specifications and Main Features

Frequently Asked Questions

User Manual