_______________General Description
The MAX3185 is a complete DTE RS-232 serial port
designed to meet the stringent ESD requirements of the
European community. All transmitter outputs and receiv-
er inputs are protected to ±15kV using IEC 1000-4-2
Air-Gap Discharge, ±8kV using IEC 1000-4-2 Contact
Discharge, and ±15kV using the Human Body Model.
The MAX3185 has three RS-232 transmitters, five RS-
232 receivers, and no charge pump, optimizing it for
operation in desktop PC and motherboard applications.
It is guaranteed to run at data rates up to 230kbps, pro-
viding compatibility with popular software for communi-
cating with personal computers. Power-supply current
is less than 300µA for IDD and ISS, and less than 1mA
for ICC.
The MAX3185 is pin and functionally compatible with
the industry-standard 75185, so existing designs can
instantly become EMC compliant. The MAX3185 is
available in an SO package and in the tiny SSOP that
further reduces board space.
________________________Applications
Desktop PC
Motherboards
Instruments
Equipment Meeting IEC1000-4-2
____________________________Features
♦Enhanced ESD Protection:
±15kV—Human Body Model
±8kV—IEC1000-4-2, Contact Discharge
±15kV—IEC1000-4-2, Air-Gap Discharge
♦Latchup Free During an ESD Event
♦20-Pin SSOP and SO Packages
♦Guaranteed 230kbps Data Rate
♦Flow-Through Pinout
♦Pin Compatible with SN75C185
♦Complete DTE Serial Port
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
________________________________________________________________
Maxim Integrated Products
1
20
19
18
17
16
15
14
13
1
2
3
4
5
6
7
8
VCC
R1OUT
R2OUT
R3OUT
R3IN
R2IN
R1IN
VDD
TOP VIEW
T1IN
T2IN
R4OUT
T3IN
T3OUT
R4IN
T2OUT
T1OUT
12
11
9
10
R5OUT
GND
VSS
R5IN
SO/SSOP
MAX3185
__________________Pin Configuration
MAX3186 MAX3185
RS-232
INTERCONNECTING
CABLE
T1
T2
T3
T4
T5
T1
T2
T3
R1
R2
R3
R1
R2
R3
R4
R5
TTL/CMOS
LOGIC
I/O
TTL/CMOS
LOGIC
I/O
__________Typical Operating Circuit
19-1076; Rev 0; 9/96
PART
MAX3185CWP
MAX3185CAP 0°C to +70°C
0°C to +70°C
TEMP. RANGE PIN-PACKAGE
20 SO
20 SSOP
______________Ordering Information
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX3185EWP -40°C to +85°C 20 SO
MAX3185EAP -40°C to +85°C 20 SSOP
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VCC = +4.5V to +5.5V, VDD = +10.8V to +13.2V, VSS = -10.8V to -13.2V, TA= TMIN to TMAX, unless otherwise noted. Typical values
are at 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.
VCC...........................................................................-0.3V to +7V
VDD.........................................................................-0.3V to +14V
VSS......................................................................... +0.3V to -14V
Input Voltages
TIN ........................................................................-0.3V to +6V
RIN ...................................................................................±30V
Output Voltages
TOUT.................................................................................±15V
ROUT.......................................................-0.3V to (VCC + 0.3V)
Short-Circuit Duration
TOUT (one at a time)...............................................Continuous
ROUT (one at a time) ..............................................Continuous
Continuous Power Dissipation (TA= +70°C)
Wide SO (derate 10.00mW/°C above +70°C)..............800mW
SSOP (derate 8.00mW/°C above +70°C) ....................640mW
Operating Temperature Ranges
MAX3185C_ P.....................................................0°C to +70°C
MAX3185E_ P..................................................-40°C to +85°C
Storage Temperature Range ............................-65°C to +160°C
Lead Temperature (soldering, 10sec) ............................+300°C
VCC = VDD = VSS = 0V, VT_OUT = ±2V
VDD = 12V, VSS = -12V, RL= 3kΩ
TIN
VDD = 7.0V, VSS = -7.0V, RL= 3kΩ
TIN
No load
No load
ROUT; ISOURCE = 1mA
No load
ROUT; ISINK = 3.2mA
CONDITIONS
V2.4RS-232 Input Threshold High V0.75RS-232 Input Threshold Low
V-25 25
Receiver Input Voltage
Operating Range
mA±35 ±60
RS-232 Output Short-Circuit
Current
Ω300Transmitter Output Resistance
V
±9.5
Output Voltage Swing ±5.0
VVCC - 0.6VOHR
Output Voltage High V0.4VOLR
Output Voltage Low
10.8 13.2VDD
4.5 5.5VCC
µA0.01 1Input Leakage Current V2.0VIHT
Input Logic Threshold High V0.8VILT
Input Logic Threshold Low
V
-13.2 -10.8VSS
Operating Voltage Range
380 1500ICC 185 500IDD µA
185 500ISS
Supply Current
UNITSMIN TYP MAXSYMBOLPARAMETER
V0.65RS-232 Input Hysteresis kΩ357RS-232 Input Resistance
mA±10
Receiver Output Short-Circuit
Current
RECEIVER INPUTS
TRANSMITTER OUTPUTS
LOGIC
DC CHARACTERISTICS
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VCC = +4.5V to +5.5V, VDD = +10.8V to +13.2V, VSS = -10.8V to -13.2V, TA= TMIN to TMAX, unless otherwise noted. Typical values
are at TA= +25°C.)
VDD = 12V, VSS = -12V, RL= 3kΩ,
CL= 1000pF, TA= +25°C
VDD = 12V, VSS = -12V,
RL= 3kΩto 7kΩ,
measured from +3V to -3V
or -3V to +3V, Figure 3,
TA= +25°C
IEC1000-4-2 (Contact Discharge)
4
Human Body Model
tPHLT
830
µs
SR
Transmitter Output
Propagation Delay, High to Low
V/µsTransition Output Slew Rate
IEC1000-4-2 (Air-Gap Discharge)
VCC = 5V, CL= 50pF, TA= +25°C
VCC = 5V, CL= 50pF, TA= +25°C
CL= 50pF to
1000pF
4.0
4.0
CONDITIONS
tPHLR
CL= 50pF to
2500pF
µs
VDD = 12V, VSS = -12V, RL= 3kΩ,
CL= 1000pF, TA= +25°C
Receiver Output
Propagation Delay, High to Low
tPLHR
4
µs
tPLHT
Receiver Output
Propagation Delay, Low to High
µs
Transmitter Output
Propagation Delay, Low to High
T3OUT = -5mA, T1OUT = T2OUT = +5mA
120
±7.5 VMouse Driveability
VCC = 5V, CL= 50pF, TA= +25°C 0.4tSKR µs
Receiver Propagation Delay
Skew, |tPLHR - tPHLR |
VCC = 5V, VDD = 12V,
VSS = -12V,
RL= 3kΩto 7kΩ,
TA= +25°C 230 kbpsDRGuaranteed Data Rate
±8
±15
VDD = 12V, VSS = -12V, RL= 3kΩ,
CL= 1000pF, TA= +25°C 0.4tSKT µs
Transmitter Propagation Delay
Skew, |tPLHT - tPHLT |
CL= 50pF to
1000pF
430
C
L
= 150pF to
2500pF
kV
±15
ESD Protection
UNITSMIN TYP MAXSYMBOLPARAMETER
ESD CHARACTERISTICS
TIMING CHARACTERISTICS
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
4 _______________________________________________________________________________________
__________________________________________Typical Operating Characteristics
(VCC = +5.0V, VDD = +12.0V, VSS = -12.0V, TA = +25°C, unless otherwise noted.)
-20
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX3185-TOC01
SUPPLY VOLTAGE (V)
SUPPLY CUREENT (mA)
-15
-10
-5
0
5
10
15
20
13.212.612.011.410.8
IDD, 240kbps
IDD, 120kbps
IDD, 20kbps 1 TRANSMITTER AT DATA RATE
2 TRANSMITTERS AT DATA RATE / 16
3kΩ + 2500pF LOAD
ICC
ISS, 20kbps
ISS, 120kbps
ISS, 240kbps
SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3185-TOC02
LOAD CAPACITANCE (pF)
SUPPLY CUREENT (mA)
25
20
15
10
5
0
-5
-10
-15
-20
-25 4000 50003000200010000
IDD, 240kbps
IDD, 120kbps
IDD, 20kbps
ICC
ISS,
20kbps ISS, 120kbps
ISS, 240kbps
1 TRANSMITTER AT DATA RATE
2 TRANSMITTERS AT DATA RATE / 16
3kΩ + CL LOAD
SLEW RATE
vs. LOAD CAPACITANCE
MAX3185-TOC03
LOAD CAPACITANCE (pF)
SLEW RATE (V/µs)
16
14
12
10
8
6
4
2
04000 50003000200010000
1 TRANSMITTER 240kbps
2 TRANSMITTERS 15kbps
3kΩ + CL LOAD
RISE
FALL
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3185-TOC04
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
12.5
10.0
7.5
5.0
2.5
0
-2.5
-5.0
-7.5
-10.0
-12.5 4000 50003000200010000
240kbps
120kbps
120kbps
240kbps
1 TRANSMITTER AT DATA RATE
2 TRANSMITTERS AT DATA RATE / 16
3kΩ + CL LOAD
MAX3185 TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CURRENT PER TRANSMITTER
MAX3185-TOC05
LOAD CURRENT PER TRANSMITTER (mA)
TRANSMITTER OUTPUT VOLTAGE (V)
15
10
5
0
-5
-10
-15 10 12 14 16 186824
0
VOUT+
VOUT-
T1
VCC
VOUT+
VOUT-
T2
T3
SLEW RATE
vs. TEMPERATURE
MAX3185-TOC06
TEMPERATURE (°C)
SLEW RATE (V/µs)
25
20
15
10
5
085 105 12545 65525-35 -15-55
RISE, 500pF
FALL, 500pF
RISE, 2000pF FALL, 2000pF
_______________Detailed Description
±15kV ESD Protection
As with all Maxim devices, ESD-protection structures
are incorporated on all pins to protect against electro-
static discharges encountered during handling and
assembly. The MAX3185 driver outputs and receiver
inputs have extra protection against static electricity
found in normal operation. Maxim’s engineers devel-
oped state-of-the-art structures to protect these pins
against ESD of ±15kV, without damage. After an ESD
event, the MAX3185 continues working without latchup.
ESD protection can be tested in several ways. The
transmitter outputs and the receiver inputs are charac-
terized for protection to the following:
1) ±15kV using the Human Body Model
2) ±8kV using the Contact-Discharge Method specified
in IEC1000-4-2 (formerly IEC801-2)
3) ±15kV using the Air-Gap Method specified in
IEC1000-4-2 (formerly IEC801-2)
ESD Test Conditions
ESD performance depends on a number of conditions.
Contact Maxim for a reliability report that documents
test setup, methodology, and results.
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
_______________________________________________________________________________________ 5
______________________________________________________________Pin Description
PIN NAME FUNCTION
1 VDD Supply-Voltage Input, +10.8V to +13.2V
12, 14, 17, 18, 19 R5OUT–R1OUT Receiver Outputs, swing between GND and VCC
16, 15, 13 T3IN, T2IN, T1IN Transmitter Inputs
10 VSS Supply-Voltage Input, -10.8V to -13.2V
11 GND Ground. Connect system to ground.
2, 3, 4, 7, 9 R1IN–R5IN Receiver Inputs
5, 6, 8 T1OUT, T2OUT, T3OUT Transmitter Outputs, swing between VDD and VSS
20 VCC Supply-Voltage Input, +4.5V to +5.5V
CHARGE-CURRENT
LIMIT RESISTOR DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
150pF
RC 50M to 100M RD 330Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
tr = 0.7ns to 1ns 30ns 60ns
t
100%
90%
10%
IPEAK
I
Figure 1a. IEC1000-4-2 ESD Test Model
Figure 1b. IEC1000-4-2 ESD-Generator Current Waveform
Human Body Model
Figure 2a shows the Human Body Model, and Figure
2b 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
1.5kΩresistor.
IEC1000-4-2
The IEC1000-4-2 standard covers ESD testing and per-
formance of finished equipment; it does not specifically
refer to integrated circuits. The MAX3185 helps you
design equipment that meets Level 4 (the highest level)
of IEC1000-4-2, without additional ESD-protection com-
ponents.
The main difference between tests done using the
Human Body Model and IEC1000-4-2 is higher peak
current in IEC1000-4-2. Because series resistance is
lower in the IEC1000-4-2 ESD test model (Figure 1a),
the ESD withstand voltage measured to this standard is
generally lower than that measured using the Human
Body Model. Figure 1b shows the current waveform for
the ±8kV IEC1000-4-2 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 stor-
age capacitor and zero-discharge resistance. It mimics
the stress caused by handling during manufacturing
and assembly. Of course, all pins (not just RS-232
inputs and outputs) require this protection during man-
ufacturing. Therefore, the Machine Model is less rele-
vant to the I/O ports than are the Human Body Model
and IEC1000-4-2.
__________Applications Information
Use proper layout to ensure other devices on your
board are not damaged in an ESD strike. Currents as
high as 60A can instantaneously pass into ground, so
be sure to minimize the ground-lead return path to the
power supply. A separate return path to the power sup-
ply is recommend. Trace widths should be greater than
40 mils. Bypass VCC, VDD, and VSS with 0.1µF capaci-
tors as close to the part as possible to ensure maxi-
mum ESD protection.
Tie any unused transmitter inputs to GND or VCC. No
external protection diodes are needed because the
MAX3185 is not sensitive to power-supply sequencing.
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
6 _______________________________________________________________________________________
CHARGE-CURRENT
LIMIT RESISTOR DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC 1M RD 1500Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
IP 100%
90%
36.8%
tRL TIMEtDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
00
AMPERES
Figure 2a. Human Body ESD Test Model Figure 2b. Human Body Model Current Waveform
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
_______________________________________________________________________________________ 7
TRANSISTOR COUNT: 217
___________________Chip Information
tF2
tF1
TPHL TPLH
tR1
tR2
1.5V
3.0V
0V
0V
DRIVER
INPUT
VOUT
VOH
VOL
3.3V
3.0V
-3.0V
-3.3V
RLCL
SIGNAL
GENERATOR
Figure 3. Slew-Rate Test Circuit and Timing Diagram
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.
8
___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
MAX3185
±15kV ESD-Pr otected, EMC-Compliant, 230kbps
RS-232 Serial Port for Motherboar ds/Desktop PCs
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.
8
___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1996 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
________________________________________________________Package Information
DIM
A
A1
B
C
E
e
H
L
MIN
0.093
0.004
0.014
0.009
0.291
0.394
0.016
MAX
0.104
0.012
0.019
0.013
0.299
0.419
0.050
MIN
2.35
0.10
0.35
0.23
7.40
10.00
0.40
MAX
2.65
0.30
0.49
0.32
7.60
10.65
1.27
INCHES MILLIMETERS
21-0042A
Wide SO
SMALL-OUTLINE
PACKAGE
(0.300 in.)
DIM
D
D
D
D
D
MIN
0.398
0.447
0.496
0.598
0.697
MAX
0.413
0.463
0.512
0.614
0.713
MIN
10.10
11.35
12.60
15.20
17.70
MAX
10.50
11.75
13.00
15.60
18.10
INCHES MILLIMETERS
PINS
16
18
20
24
28
1.27
0.050
L
HE
D
e
A
A1 C
0°- 8°
0.101mm
0.004in.
B
L
DIM
A
A1
B
C
D
E
e
H
L
α
DIM
D
D
D
D
D
MIN
0.068
0.002
0.010
0.004
0.205
0.301
0.025
0˚
MIN
0.239
0.239
0.278
0.317
0.397
MAX
0.078
0.008
0.015
0.008
0.209
0.311
0.037
8˚
MAX
0.249
0.249
0.289
0.328
0.407
MIN
1.73
0.05
0.25
0.09
5.20
7.65
0.63
0˚
MIN
6.07
6.07
7.07
8.07
10.07
MAX
1.99
0.21
0.38
0.20
5.38
7.90
0.95
8˚
PINS
14
16
20
24
28
MAX
6.33
6.33
7.33
8.33
10.33
INCHES
INCHES
MILLIMETERS
MILLIMETERS
α
SSOP
SHRINK
SMALL-OUTLINE
PACKAGE
HE
D
A
A1
C
B
0.65 BSC0.0256 BSC
21-0056A
e
SEE VARIATIONS
