MAX3098EBESE+T [MAXIM]
Line Receiver, 3 Func, 3 Rcvr, CMOS, PDSO16, 0.150 INCH, SOIC-16;
| 型号： | MAX3098EBESE+T |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Line Receiver, 3 Func, 3 Rcvr, CMOS, PDSO16, 0.150 INCH, SOIC-16 光电二极管 接口集成电路 |
| 文件： | 总16页 (文件大小：360K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-1727; Rev 0; 7/00
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
General Description
Features
The MAX3097E/MAX3098E feature three high-speed RS-
485/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.
ꢀ Detects the Following RS-485 Faults:
Open-Circuit Condition
Short-Circuit Condition
Low Differential Voltage Signal
Common-Mode Range Violation
The MAX3097E/MAX3098E indicate when a receiver
input is in an open-circuit condition, short-circuit condi-
tion, 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 thresh-
old values.
ꢀ ESD Protection
±±5ꢀVꢁ—uman ꢂodꢃ Model
±±5ꢀVꢁꢄEC ±111-4-ꢅ2 ꢆir-ꢇap Discharge
Method
±8ꢀVꢁꢄEC ±111-4-ꢅ2 Contact Discharge Method
The fault circuitry includes a capacitor-programmable
delay to ensure that there are no erroneous fault condi-
tions even at slow edge rates. Each receiver is capable
of accepting data at rates up to 32Mbps.
ꢀ Single +3V to +5.5V Operation
ꢀ -±1V to +±3.ꢅV Extended Common-Mode Range
ꢀ Capacitor-Programmable Delaꢃ of Fault ꢄndication
ꢆllows Error-Free Operation at Slow Data Rates
ꢀ ꢄndependent and Universal Fault Outputs
ꢀ 3ꢅMbps Data Rate
________________________Applications
RS-485/RS-422 Receivers for Motor-Shaft
Encoders
ꢀ ±6-Pin QSOP is 41% Smaller than ꢄndustrꢃ-
Standard ꢅ6LS3±/3ꢅ Solutions
High-Speed, Triple RS-485/RS-422 Receiver with
Extended Electrostatic Discharge (ESD)
Triple RS-485/RS-422 Receiver with Input Fault
Indication
Ordering Information
PIN-
PACKAGE
PART
TEMP. RANGE
Telecommunications
Embedded Systems
MAX3097ECEE
0°C to +70°C
0°C to +70°C
16 QSOP
16 SO
MAX3097ECSE
Ordering Information continued at end of data sheet.
Typical Application Circuit
ENCODED SIGNALS
A, A, B, B, Z, Z
-in Configuration
TOP VIEW
MAX3097E
MAX3098E
A
1
2
3
4
5
6
7
8
16 V
CC
A
15 ALARMA
14 OUTA
RECEIVER
OUTPUTS
ALARM
OUTPUTS
B
MOTOR
CONTROLLER
DSP
B
Z
MAX3097E
MAX3098E
13 ALARMB
12 OUTB
8
MOTOR
MAX547
12-BIT D/A
Z
11 ALARMZ
10 OUTZ
GND
DELAY
9
ALARMD
MOTOR DRIVER
QSOP/SO/DIP
________________________________________________________________ Maxim Integrated Products
±
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.
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (V ).............................................................+7V
Operating Temperature Ranges
CC
Receiver Input Voltage (A, A, B, B, Z, Z)............................. 25V
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
Output Voltage (OUT_, ALARM_)...............-0.3V to (V
DELAY ........................................................-0.3V to (V
+ 0.3V)
+ 0.3V)
CC
CC
Continuous Power Dissipation (T = +70°C)
A
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
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.
ELECTRICAL CHARACTERISTICS
(V
= +3V to +5.5V, T = T
A
to T
, unless otherwise noted. Typical values are at V
= +5V and T = +25°C.)
CC A
CC
MIN
MAX
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
5.5
UNITS
V
Supply Voltage Range
Supply Current
V
3
CC
I
No load
-10V ≤ V
-10V ≤ V
3.1
4.0
mA
CC
Receiver Differential Threshold
Voltage (Note 1)
V
≤ 13.2V
-200
+200
mV
mV
TH
CM
CM
Receiver Input Hysteresis
∆V
≤ 13.2V
40
TH
V
V
V
V
= 4.75V, I = -4mA, V = 200mV
V
- 1.5
CC
CC
CC
CC
O
ID
CC
CC
Output High Voltage
V
V
OH
= 3.0V, I = -1mA, V = 200mV
V
- 1.0
O
ID
= 4.75V, I = +4mA, V = -200mV
0.4
0.4
160
O
ID
Output Low Voltage
V
V
OL
= 3.0V, I = +1mA, V = -200mV
O
ID
Receiver Input Resistance
R
-10V ≤ V
≤ 13.2V
CM
90
kΩ
IN
V
= 13.2V
IN
0.07
0.14
(Note 2)
Input Current
(A , A , B , B (Z , Z )
I
V
= 0 or 5.5V
CC
mA
mA
IN
V
= -10V
IN
-0.05
-0.11
105
(Note 2)
Output Short-Circuit Current
I
0 ≤ V ≤ V
RO CC
OSR
FAULT DETECTION
MAX3097E Fault-Detection
Receiver Differential Threshold
Voltage (Note 3)
F
High limit
Low limit
High limit
Low limit
275
-475
0.12
-0.20
475
-275
0.20
-0.12
DIFH
V
V
= 0
= 0
mV
V
CM
CM
F
DIFL
MAX3098EA Fault-Detection
Receiver Differential Threshold
Voltage (Note 3)
F
DIFH
F
DIFL
2
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
ELECTRICAL CHARACTERISTICS (continued)
(V
= +3V to +5.5V, T = T
A
to T
, unless otherwise noted. Typical values are at V
= +5V and T = +25°C.)
CC A
CC
MIN
MAX
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
MAX3098EB Fault-Detection
Receiver Differential Threshold
Voltage (Note 3)
F
High limit
Low limit
70
250
DIFH
V
= 0
mV
CM
F
-250
13.2
-70
DIFL
F
High limit
Low limit
CMH
Fault-Detection Common-Mode
Voltage Range (Note 4)
V
µA
V
F
-10
11
CML
DELAY Current Source
V
V
V
= 5V, V
= 3V
= 0
DELAY
9
10
CC
CC
CC
1.55
3.1
1.73
3.29
1.90
3.5
DELAY Threshold
= 5V
ESD PROTECTION
Human Body Model
15
15
8
ESD Protection
(A, A, B, B, Z, Z)
kV
IEC1000-4-2 (Air-Gap Discharge)
IEC1000-4-2 (Contact Discharge)
SWITCHING CHARACTERISTICS
(V
= +3V to +5.5V, V
=
3.0V, T = T
to T
, unless otherwise noted. Typical values are at V = +5V and T = +25°C.)
CC A
CC
ID
A
MIN
MAX
PARAMETER
SYMBOL
, t
CONDITIONS
MIN
TYP
MAX
75
UNITS
ns
V
V
= 4.5V to 5.5V
= 3.0V to 3.6V
CC
CC
Propagation Delay from Input to
Output
C = 15pF,
L
Figures 1, 2
t
PLH PHL
85
Receiver Skew |t
- t
|
t
C = 15pF, Figures 1, 2
L
10
ns
PLH PHL
SKEW
Channel-to-Channel
Propagation Delay Skew
C = 15pF, Figures 1, 2
L
10
ns
Maximum Data Rate
f
C = 15pF, Figure 1
L
32
Mbps
MAX
FAULT DETECTION
t
15
DFLH
DFHL
Differential Fault Propagation
Delay to Output (Note 5)
C
= 15pF, Figures 1, 3
µs
V/µs
µs
LF
t
1.2
MAX3097E (Note 6)
MAX3098E (Note 7)
1.0
Minimum Differential Slew Rate
to Avoid False Alarm Output
0.33
Common-Mode Fault
Propagation Delay to Output
(Note 5)
t
t
15
CMFLH
CMFHL
C = 15pF, Figures 1, 4
L
1.5
Note 1: V
is the common-mode input voltage. V is the differential input voltage.
ID
CM
Note 2: V is the input voltage at pins A, A, B, B, Z, Z.
IN
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
Note 7: Equivalent pulse test: 0.62V / (t
- t
) ≥ SR .
DFLH DFHL D
- t
) ≥ SR .
DFLH DFHL D
_______________________________________________________________________________________
3
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
Typical Operating Characteristics
(Typical values are at V
= +5V and T = +25°C.)
A
CC
SUPPLY CURRENT vs.
TEMPERATURE
ALARMD OUTPUT DELAY
vs. CAPACITANCE
RECEIVER PROPAGATION DELAY
vs. TEMPERATURE
5
4
3
2
1
0
10,000
1000
100
70
60
NO LOAD
V
= 3.3V
CC
V
= 5.0V
= 3.3V
CC
V
CC
50
40
30
V
= 5.0V
CC
V
V
= 5V
= 3V
CC
CC
10
1
20
TEMPERATURE (°C)
80
-40
-20
0
40
60
10
100
CAPACITANCE (pF)
1000
1
10,000
20
TEMPERATURE (°C)
80
-40
-20
0
40
60
RECEIVER OUTPUT HIGH VOLTAGE
vs. OUTPUT CURRENT
RECEIVER OUTPUT LOW VOLTAGE
vs. OUTPUT CURRENT
DELAYED ALARM OUTPUT
6
5
4
5.0
4.5
4.0
V
= 5.0V
CC
CH 1
GND
V
= 5.0V
CC
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 3.3V
CC
3
2
1
0
V
= 3.3V
CC
GND
GND
CH 2
CH 3
20µs/div
0
5
10
15
20
25
30
-45 -40 -35 -30 -25 -20 -15 -10 -5
OUTPUT CURRENT (mA)
0
CH1: V , 5V/div
A
OUTPUT CURRENT (mA)
CH2: V
CH3: V
, 5V/div
, 5V/div
ALARMA
ALARMD
V = GND, C
= 270pF
A
DELAY
4
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
Typical Operating Characteristics (continued)
(Typical values are at V
= +5V and T = +25°C.)
A
CC
COMMON-MODE VOLTAGE FAULT
(HIGH SIDE)
MAX3097E
LOW DIFFERENTIAL INPUT FAULT
COMMON-MODE VOLTAGE FAULT
(LOW SIDE)
GND
CH 1
GND
CH 1
CH 2
GND
GND
CH 1
CH 2
CH 3
CH 2
CH 3
GND
GND
GND
GND
2ms/div
2ms/div
100µs/div
CH1: V + AC(60Hz), 10V/div
CH1: V + AC(60Hz), 10V/div
CH1: V , 200mV/div
ALARMA
V = GND
A
A
A
A
CH2: V
CH3: V
, 5V/div
CH2: V
CH3: V
, 5V/div
CH2: V
, 5V/div
OUTA
ALARMA
= 3V
OUTA
ALARMA
= 3V
, 5V/div
, 5V/div
V
V
CC
CC
FAULT-DETECTION RECEIVER DIFFERENTIAL
THRESHOLD VOLTAGE SHIFT vs.
COMMON-MODE VOLTAGE
SLEW-RATE FAULT
12
CH 1
CH 2
GND
GND
8
4
MAX3097E
0
MAX3098E
-4
-8
-10
-5
0
5
10
CH1: V , 5V/div
A
CH2: V
, 5V/div
ALARMA
SLEW RATE = 0.05V/µs
V = GND
A
COMMON-MODE VOLTAGE (V)
_______________________________________________________________________________________
5
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
-in Description
PIN
NAME
FUNCTION
1
A
Noninverting Receiver A Input
Inverting Receiver A Input
Noninverting Receiver B Input
Inverting Receiver B Input
Noninverting Receiver Z Input
Inverting Receiver Z Input
Ground
2
3
4
5
6
7
A
B
B
Z
Z
GND
Programmable Delay Terminal. Connect a capacitor from DELAY to GND to set the
ALARMD output delay time. To obtain a minimum delay, leave DELAY unconnected. See
Capacitance vs. ALARMD Output Delay in the Typical Operating Characteristics.
8
9
DELAY
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.
ALARMD
Z Receiver Output. If V - V ≥ +200mV, OUTZ will be high. If V - V ≤ -200mV, OUTZ will
Z
Z
Z
Z
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.
10
11
OUTZ
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.
ALARMZ
B Receiver Output. If V - V ≥ +200mV, OUTB will be high. If V - V ≤ -200mV, OUTB will
B
B
B
B
12
13
14
OUTB
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.
ALARMB
A Receiver Output. If V - V ≥ +200mV, OUTA will be high. If V - V ≤ -200mV, OUTA will
A
A
A
A
OUTA
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.
15
16
ALARMA
V
Power Supply
CC
6
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
The MAX3097E/MAX3098E are designed for motor-
Detailed Description
shaft encoders with standard A, B, and Z outputs (see
The MAX3097E/MAX3098E feature high-speed, triple
Using the MAX3097E/MAX3098E as Shaft Encoder
RS-485/RS-422 receivers with fault-detection circuitry
Receivers). The devices provide an alarm for open-cir-
and fault-status outputs. The fault outputs are active
cuit conditions, short-circuit conditions, data nearing
push-pull, requiring no pull-up resistors. The fault cir-
the minimum differential threshold conditions, data
cuitry includes a capacitor-programmable delayed
below the minimum threshold conditions, and receiver
FAULT_ output to ensure that there are no erroneous
inputs outside the input common-mode range. Tables 1
fault conditions even at slow edge rates (see Delayed
and 2 are functional tables for each receiver.
Fault Output). The receivers operate at data rates up to
32Mbps.
Test Circuits and Waveforms
ALARMA
OR (FAULT OUTPUT)
ALARMD
+3V
-3V
C
RISE/FALL TIMES ≤2ns
LF
A
A
OV
OV
V
ID
V
A
V
OUTA
t
PHL
t
ID
PLH
V
C
OH
L
V
/2
V /2
CC
CC
R
O
V
A
V
OL
Figure 1. Typical Receiver Test Circuit
Figure 2. Propagation Delay
F
CMH
IN
V
+3.0V
OV
F
DIFH
OV
V
ID
F
F
CML
DIFL
-3.0V
t
t
DFHL
DFLH
V
OH
V
/2
V /2
CC
CC
ALARM OR ALARMD
t
t
t
t
CMFLH
CMFHL CMFLH
CMFHL
/2
V
OL
V
OH
V
/2
CC
V /2
CC
V
/2
V
CC
CC
ALARM OR ALARMD
V
OL
Figure 4. Common-Mode Fault Propagation Delay
Figure 3. Fault-Detection Timing
_______________________________________________________________________________________
7
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
Table 1. MAX3097E Alarm Function Table (Each Receiver)
INPUTS
OUTPUTS
V
ALARMD
t ≥ DELAY
(NOTE 1)
ID
FAULT CONDITION
COMMON-MODE
VOLTAGE
(DIFFERENTIAL
INPUT VOLTAGE)
OUT_
ALARM_
≥0.475V
1
1
0
0
Normal Operation
Indeterminate
<0.475V and ≥0.275V
Indeterminate
Indeterminate
<0.275V and ≥0.2V
1
1
1
1
1
Low Input Differential Voltage
Indeterminate
(Note 2)
≤0.2V and ≥-0.2V
Low Input Differential Voltage
Low Input Differential Voltage
≤13.2V and ≥-10V
≤-0.2V and >-0.275V
0
0
0
1
1
≤-0.275V and
>-0.475V
Indeterminate
0
Indeterminate
0
Indeterminate
≤-0.475V
Indeterminate
(Note 3)
Outside Common-Mode
Voltage Range
X
<-10V or >+13.2V
1
1
X = Don’t care
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.
Table 2. MAX3098EA Alarm Function Table (Each Receiver)
INPUTS
OUTPUTS
V
ALARMD
t ≥ DELAY
(NOTE 1)
ID
FAULT CONDITION
COMMON-MODE
VOLTAGE
(DIFFERENTIAL
INPUT VOLTAGE)
OUT_
ALARM_
≥0.2V
1
0
0
Normal Operation
Indeterminate
Indeterminate
<0.2V and ≥0.12V
Indeterminate
Indeterminate
≤13.2V and ≥-
Indeterminate
(Note 2)
<0.12V and ≥-0.12V
1
1
Low Input Differential Voltage
10V
Indeterminate
0
≤-0.12V and ≥ -0.2V
≤-0.2V
Indeterminate
0
Indeterminate
0
Indeterminate
Normal Operation
Outside Common-Mode Voltage
Range
<-10V or
>+13.2V
Indeterminate
(Note 3)
X
1
1
X = Don’t care; for B-grade functionality, replace V input values in Table 2 with B-grade parameters from Electrical Characteristics.
ID
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.
8
_______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
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 inte-
grated circuits. The MAX3097E/MAX3098E help you
design equipment that meets Level 4 (the highest level)
of IEC 1000-4-2, without additional ESD-protection com-
ponents.
±±15k EꢀD -rotection
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 pro-
tection against static electricity found in normal opera-
tion. 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.
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 gen-
erally 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.
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.
Machine Model
The Machine Model for ESD testing uses a 200pF stor-
age 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.
Human Body Model
Figure 5a shows the Human Body Model, and Figure
5b shows the current waveform it generates when dis-
charged into a low impedance. This model consists of
a 100pF capacitor charged to the ESD voltage of inter-
est, which is then discharged into the device through a
1.5kΩ resistor.
R
R
D
1.5k
C
1MΩ
I
P
100%
90%
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
I
r
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
AMPERES
36.8%
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
C
STORAGE
CAPACITOR
s
100pF
10%
0
SOURCE
TIME
0
t
RL
t
DL
CURRENT WAVEFORM
Figure 5b. Human Body Model Current Waveform
Figure 5a. Human Body ESD Test Model
_______________________________________________________________________________________
9
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
___________Applications Information
R
R
C
D
50MΩ to 100MΩ
330Ω
Using the MAX3097E/MAX3098E as ꢀhaft
Encoder Receivers
DISCHARGE
RESISTANCE
CHARGE-CURRENT
LIMIT RESISTOR
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) tech-
niques are used to count the pulses and provide feed-
back of both shaft position and shaft velocity for a
stable positioning system.
HIGH-
VOLTAGE
DC
DEVICE
UNDER
TEST
C
s
150pF
STORAGE
CAPACITOR
SOURCE
Figure 6a. IEC 1000-4-2 ESD Test Model
I
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).
100%
90%
Detecting Faults
Signal integrity from the shaft encoder to the DSP is
essential for reliable system operation. Degraded sig-
nals could cause problems ranging from simple mis-
counts 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 sig-
nal, open-circuit wires, short-circuit wires, and an input
signal outside the common-mode input voltage range
of the receiver.
10%
t = 0.7ns to 1ns
r
t
30ns
60ns
Figure 6b. IEC 1000-4-2 ESD Generator Current Waveform
A
A
Detecting ꢀhort 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.
B
B
Z
Detecting OpenꢁCircuit Conditions
Detecting an open-circuit condition is similar to detect-
ing a short-circuit condition and relies on the terminat-
ing 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
Z
Figure 7. Typical Shaft Encoder Output
condition, V is approximately 0 and a fault occurs.
ID
10 ______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
ground. Upon activation of any alarm from receiver A,
B, or Z, the MOSFET is turned off, allowing the current
CommonꢁMode Range
The MAX3097E/MAX3098E contain circuitry that de-
tects if the input stage is going outside its useful com-
mon-mode range. If the received data could be
unreliable, a fault signal is triggered.
source to charge C
. When V
exceeds the
DELAY
DELAY
DELAY threshold, the comparator output, ALARMD,
goes high. ALARMD is reset when all receiver alarms
go low, quickly discharging C
to ground.
DELAY
Detecting Low Input Differential
ꢀetting Delay Time
Due to cable attenuation on long wire runs, it is possi-
ALARMD’s delay time is set with a single capacitor
ble that V < 200mV, and incorrect data will be
ID
connected from DELAY to GND. The delay comparator
received. In this condition, a fault will be indicated.
threshold varies with supply voltage, and the C
DELAY
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.
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:
t = 15 + 0.33 x C
(for V
CC
= 5V)
D
DELAY
and
Figure 9 shows the delayed alarm output.
t = 10 + 0.187 x C
(for V
CC
= 3V)
D
DELAY
ALARMD performs a logic OR of ALARMA, ALARMB,
and ALARMZ (Figure 10). A NOR gate drives an N-
channel MOSFET so that in normal operation with no
faults, the current source (10µA typ) is shunted to
where t is in µs and C
D
is in pF.
DELAY
DELAY
CURRENT
SOURCE
A
A
DELAY
COMPARATOR
ALARMD
ALARMA
ALARMB
ALARMZ
C
*
NORMAL OPERATION
SHORT CIRCUIT A TO A
NMOS
G1
DELAY
(EXTERNAL)
Figure 8. Short-Circuit Detection
t
DLY
ALARMA
ALARMB
ALARM_
DELAY
DELAY THRESHOLD
ALARMD
t
D
t
D
*The capacitor (C
If the duration of an ALARM_ pulse is less than t , no alarm
) charges up slowly, but discharges rapidly.
DELAY
ALARMD
DLY
output will be present at ALARMD.
Figure 9. Delayed Alarm Output
Figure 10. ALARMD Simplified Schematic
______________________________________________________________________________________ 11
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
Ordering Information (continued)
Functional Diagram
PIN-
PACKAGE
PART
TEMP. RANGE
V
CC
MAX3097ECPE
MAX3097EEEE
MAX3097EESE
MAX3097EEPE
MAX3098EACEE
MAX3098EACSE
MAX3098EACPE
MAX3098EAEEE
MAX3098EAESE
MAX3098EAEPE
MAX3098EBCEE
MAX3098EBCSE
MAX3098EBCPE
MAX3098EBEEE
MAX3098EBESE
MAX3098EBEPE
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
16 Plastic DIP
16 QSOP
16 SO
ALARMA
OUTA
A
A
ALARMB
OUTB
16 Plastic DIP
16 QSOP
16 SO
B
B
ALARMZ
OUTZ
16 Plastic DIP
16 QSOP
16 SO
Z
Z
ALARMD
DELAY
16 Plastic DIP
16 QSOP
16 SO
MAX3097E
MAX3098E
GND
16 Plastic DIP
16 QSOP
16 SO
16 Plastic DIP
Chip Information
TRANSISTOR COUNT: 675
PROCESS: CMOS
12 ______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
-ac5age Information
______________________________________________________________________________________ 13
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
-ac5age Information (continued)
14 ______________________________________________________________________________________
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
-ac5age Information (continued)
______________________________________________________________________________________ 15
±±15k EꢀDꢁ-rotected, 32Mbps, 3k/1k,
Triple Rꢀꢁ422/Rꢀꢁ481 Receivers with Fault Detection
NOTES
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 -roducts, ±20 ꢀan Gabriel Drive, ꢀunnyvale, CA 94086 408ꢁ737ꢁ7600
© 2000 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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