19-2443; Rev 1; 2/03
±50V Isolated, 3.0V to 5.5V,
250kbps, 2 Tx/2 Rx, RS-232 Transceiver
General Description
The MAX3250 is a 3.0V to 5.5V powered, ±50V isolated
EIA/TIA-232 and V.28/V.24 communications interface
with high data-rate capabilities. The MAX3250 is a dual
die part that operates with up to ±50V difference
between the RS-232 side and the logic side (ISOCOM
to GND). This makes the device ideal for operation in
noisy conditions with high common-mode voltages.
This feature prevents damage to the device if RS-232
lines are inadvertently short-circuited to a +24V or ±48V
power bus.
The MAX3250 is powered by a single 3V to 5.5V supply
on the logic side. Power is transferred from the logic
side to the isolated side by ±100V external capacitors.
The MAX3250 has two receivers (Rx) and two drivers
(Tx) and is guaranteed to run at data rates of 250kbps
while maintaining RS-232 output levels. The trans-
ceivers have a proprietary low-dropout transmitter out-
put stage, delivering true RS-232 performance from a
3V to 5.5V supply with a dual charge pump. The device
features a
FAULT
open-drain output to signal an exces-
sive isolated-side voltage condition on any of the RS-
232 inputs. This output can drive an alarm LED or can
be monitored by the processor to prevent operation
under these conditions. The receiver outputs are high
impedance in shutdown, allowing multiple interfaces
(IrDA, RS-232, RS-485) to be connected to the same
UART.
The MAX3250 is available in a space-saving 28-pin
SSOP package.
o
±50V Isolation
o
20µA Supply Current in Shutdown
o
250kbps Guaranteed Data Rate
o
FAULT
Output
o
High-Impedance Transmitter and Receiver
Outputs in Shutdown
o
Space-Saving SSOP Package
o
Inductorless/Transformerless Design Simplifies
EMI Compliance
o
Low-Cost Replacement for Opto-Isolated
Transceivers
o
Meets EIA/TIA-232 Specifications Down to 3.0V
Features
MAX3250
Ordering Information
PART
MAX3250CAI
MAX3250EAI
TEMP RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
28 SSOP
28 SSOP
Pin Configuration
TOP VIEW
C1- 1
R1OUT 2
R2OUT 3
T1IN 4
T2IN 5
N.C. 6
N.C. 7
C1+ 8
C3+ 9
V+ 10
C3- 11
C4+ 12
C4- 13
28 V
CC
27 C2-
26 GND
25 FAULT
24 SHDN
Applications
Industrial Control
Programmable Logic Controller
Point-of-Sale Equipment
PC-to-Router Connections
Diagnostic Ports
Telecom Equipment
MAX3250
23 N.C.
22 N.C.
21 C2+
20 ISOV
CC
19 R1IN
18 R2IN
17 T1OUT
16 T2OUT
15 ISOCOM
Typical Operating Circuit appears at end of data sheet.
V- 14
SSOP
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
±50V Isolated, 3.0V to 5.5V,
250kbps, 2 TX/2 RX, RS-232 Transceiver
MAX3250
ABSOLUTE MAXIMUM RATINGS
All Voltages Referenced to GND, Unless Otherwise Noted.
V
CC
...........................................................................-0.3V to +6V
ISOCOM...............................................................................±80V
ISOV
CC
to ISOCOM..................................................-0.3V to +6V
V+ to ISOCOM (Note 1)............................................-0.3V to +7V
V- to ISOCOM (Note 1)............................................+0.3V to -7V
V+ + |V-| (Note 1) ...................................................................13V
Input Voltages
T_IN,
SHDN
...........................................................-0.3V to +6V
R_IN to ISOCOM...............................................................±25V
Output Voltages
T_OUT to ISOCOM ........................................................±13.2V
R_OUT .....................................................-0.3V to (V
CC
+ 0.3V)
FAULT....................................................................-0.3V
to +6V
C1-, C2- ......................................................-0.3V to (V
CC
+ 0.3V)
C1+, C2+, C3+, C3-, C4+, C4-
to ISOCOM ......................................-0.3V to (ISOV
CC
+ 0.3V)
T_OUT Current ..............30mA (continuous), 50mA (peak, 10µs)
R_IN Current..................30mA (continuous), 50mA (peak, 10µs)
ISOCOM Current ...........30mA (continuous), 50mA (peak, 10µs)
Short-Circuit Duration T_OUT to ISOCOM .................Continuous
Continuous Power Dissipation (T
A
= +70°C)
28-Pin SSOP (derate 9.5mW/°C above +70°C) ...........762mW
Operating Temperature Ranges
MAX3250CAI .....................................................0°C to +70°C
MAX3250EAI...................................................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Note 1:
V+ and V- can have a maximum magnitude of 7V, but their absolute difference cannot exceed 13V.
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
CC
= 3.0V to 5.5V, see
Typical Operating Circuit
and Table 1 for capacitor values, ISOCOM = GND, T
A
= T
MIN
to T
MAX
, unless oth-
erwise noted. Typical values are at V
CC
= 3.3V and T
A
= +25°C.) (Note 2)
PARAMETER
DC CHARACTERISTICS
Supply Current
Supply Current Shutdown
Maximum Ground Differential
Isolation Resistance
LOGIC INPUTS
Input Logic Low
Input Logic High
Transmitter Input Hysteresis
Input Leakage Current
RECEIVER OUTPUTS
Output Leakage Current
Output Voltage Low
Output Voltage High
FAULT OUTPUT
Output Voltage Low
(Open Drain)
Output Leakage Current
FAULT
Trip Level
SHDN
= GND
I
OUT
= 1.6mA
I
OUT
= -1.0mA
V
CC
- 0.6 V
CC
- 0.1
-10
±0.05
+10
0.4
µA
V
V
T_IN,
SHDN
-1
T_IN,
SHDN
T_IN,
SHDN
V
CC
= 3.3V
V
CC
= 5.0V
2.0
2.4
0.5
±0.01
+1
0.8
V
V
V
µA
SHDN
= V
CC
, no load
SHDN
= GND, V
ISOCOM
= GND
SHDN
= GND, V
ISOCOM
=
±50V
|V
GND
- V
ISOCOM
|
Between GND and ISOCOM
60
15
20
35
45
±350
50
mA
µA
V
kΩ
CONDITIONS
MIN
TYP
MAX
UNITS
I
OUT
= 5mA
FAULT
not asserted
|V
GND
- V
ISOCOM
|
55
0.4
1
V
µA
V
2
_______________________________________________________________________________________
±50V Isolated, 3.0V to 5.5V,
250kbps, 2 TX/2 RX, RS-232 Transceiver
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= 3.0V to 5.5V, see
Typical Operating Circuit
and Table 1 for capacitor values, ISOCOM = GND, T
A
= T
MIN
to T
MAX
, unless oth-
erwise noted. Typical values are at V
CC
= 3.3V and T
A
= +25°C.) (Note 2)
PARAMETER
RECEIVER INPUTS
(relative to ISOCOM)
Input Voltage Range
Input Threshold Low
Input Threshold High
Input Hysteresis
Input Resistance
Output Voltage Swing
Output Resistance
Output Short-Circuit Current
Output Leakage Current
V
CC
= 0 or 3V to 5.5V, T_OUT =
±12V,
SHDN
= GND
T
A
= +25°C
All transmitter outputs loaded with 3kΩ to ISOCOM
ISOV
CC
= V+ = V- = 0V, T_OUT =
±2V
3
±5.0
300
-60
-25
TRANSMITTER OUTPUTS
(relative to ISOCOM)
±5.4
10M
+60
+25
V
Ω
mA
µA
T
A
= +25°C
T
A
= +25°C
V
CC
= 3.3V
V
CC
= 5.0V
V
CC
= 3.3V
V
CC
= 5.0V
2.4
2.4
-25
1.2
1.3
1.6
1.7
0.5
5
7
+25
0.6
0.8
V
V
V
V
kΩ
CONDITIONS
MIN
TYP
MAX
UNITS
MAX3250
TIMING CHARACTERISTICS
(V
CC
= 3.0V to 5.5V, see
Typical Operating Circuit
and Table 1 for capacitor values, ISOCOM = GND, T
A
= T
MIN
to T
MAX
, unless oth-
erwise noted. Typical values are at V
CC
= 3.3V and T
A
= +25°C.)
PARAMETER
Maximum Data Rate
Receiver Propagation Delay
Receiver Skew
Transmitter Skew
CONDITIONS
R
L
= 3kΩ, C
L
= 1000pF to ISOCOM, one transmitter
R_IN to R_OUT, C
L
= 150pF to GND
|t
PHL
- t
PLH
|
|t
PHL
- t
PLH
|
(Note 3)
V
CC
= 3.3V, T
A
= +25°C,
R
L
= 3kΩ to 7kΩ to ISOCOM,
measured from +3V to -3V or
-3V to +3V
C
L
= 150pF to 1000pF
to ISOCOM
C
L
= 150pF to 2500pF
to ISOCOM
6
4
0.3
0.5
V
ISOCOM
= GND
V
ISOCOM
=
±50V
300
350
MIN
250
0.4
100
120
30
V/µs
30
µs
µs
µs
TYP
MAX
UNITS
kbps
µs
ns
ns
Transition-Region Slew Rate
FAULT
Propagation Delay
Time to Shutdown
Time to Exit Shutdown
Note 2:
All currents into the device are positive; all currents out of the device are negative. All voltages are referenced to device
ground, unless otherwise noted.
Note 3:
Transmitter skew is measured at the transmitter zero crosspoints.
_______________________________________________________________________________________
3
±50V Isolated, 3.0V to 5.5V,
250kbps, 2 TX/2 RX, RS-232 Transceiver
MAX3250
Typical Operating Characteristics
(V
CC
= 3.3V, 250kbps data rate, see
Typical Operating Circuit
and Table 1 for capacitor values, all transmitters loaded with 3kΩ and
C
L
to ISOCOM, T
A
= +25°C, unless otherwise noted.)
TRANSMITTER OUTPUT VOLTAGE
vs. LOAD CAPACITANCE
MAX3250 toc01
SLEW RATE
vs. LOAD CAPACITANCE
MAX3250 toc02
OPERATING SUPPLY CURRENT
vs. LOAD CAPACITANCE
80
SUPPLY CURRENT (mA)
70
60
50
40
30
20
120kbps
20kbps
250kbps
T1 TRANSMITTING AT 250kbps
T2 TRANSMITTING AT 20kbps
MAX3250 toc03
8
TRANSMITTER OUTPUT VOLTAGE (V)
6
V
OUT+
4
2
0
-2
-4
-6
0
1000
2000
3000
4000
V
OUT-
T1 TRANSMITTING AT 250kbps
T2 TRANSMITTING AT 20kbps
30
25
SLEW RATE (V/µs)
20
15
10
5
FOR DATA RATES UP TO 250kbps
0
+SLEW
-SLEW
90
10
0
4000
5000
0
1000
2000
3000
4000
5000
5000
0
1000
2000
3000
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
LOAD CAPACITANCE (pF)
TIME TO EXIT SHUTDOWN
V
ISOCOM
= 0V
SHUTDOWN CURRENT
vs. TEMPERATURE
SHDN
5V/div
SUPPLY CURRENT (µA)
ISOCOM = -50V
MAX3250 toc05
MAX3250 toc04
400
300
200
100
0
-100
-200
-300
ISOCOM = +50V
TOUT
5V/div
ISOCOM = 0V
100µs/div
-40
-15
10
35
60
85
TEMPERATURE (°C)
PEAK GROUND OFFSET VOLTAGE
vs. FREQUENCY
V
CC
= 5V
50
PEAK GROUND OFFSET (±V)
40
30
20
10
0
0
100
200
300
400
500
600
V
CC
= 3.3V
MAX3250 toc06
COMMON-MODE FAULT RESPONSE
MAX3250 toc07
60
ISOCOM
50V/div
FAULT
5V/div
4ms/div
FREQUENCY (Hz)
4
_______________________________________________________________________________________
±50V Isolated, 3.0V to 5.5V,
250kbps, 2 TX/2 RX, RS-232 Transceiver
Pin Description
PIN
1
2
3
4
5
6, 22, 23
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
24
25
26
27
28
NAME
C1-
R1OUT
R2OUT
T1IN
T2IN
N.C.
N.C.
C1+
C3+
V+
C3-
C4+
C4-
V-
ISOCOM
T2OUT
T1OUT
R2IN
R1IN
ISOV
CC
C2+
SHDN
FAULT
GND
C2-
V
CC
FUNCTION
Negative Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C1- to C1+.
See Table 1 for values.
TTL/CMOS Receiver Output
TTL/CMOS Receiver Output
TTL/CMOS Transmitter Input
TTL/CMOS Transmitter Input
No Connection. Not internally connected.
No Connection. Leave unconnected or connect to ISOCOM.
Positive Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C1+ to C1-.
See Table 1 for values.
Positive Terminal of the Voltage-Doubler Charge-Pump Capacitor. Connect a 0.1µF capacitor from
C3+ to C3-.
+5.5V Generated by the Charge Pump, Referenced to ISOCOM. Bypass V+ to ISOCOM with a
0.47µF capacitor.
Negative Terminal of the Voltage-Doubler Charge-Pump Capacitor. Connect a 0.1µF capacitor from
C3- to C3+.
Positive Terminal of the Inverting Charge-Pump Capacitor. Connect a 0.47µF capacitor from
C4+ to C4-.
Negative Terminal of the Inverting Charge-Pump Capacitor. Connect a 0.47µF capacitor from
C4- to C4+.
-5.5V Generated by the Charge Pump, Referenced to ISOCOM. Bypass V- to ISOCOM with a 0.47µF
capacitor.
Isolated Ground
RS-232 Transmitter Output
RS-232 Transmitter Output
RS-232 Receiver Input
RS-232 Receiver Input
Internally Generated Isolated Power-Supply Voltage, Referenced to ISOCOM. Bypass ISOV
CC
to
ISOCOM with a 1µF capacitor.
Positive Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C2+ to C2-.
See Table 1 for values.
Shutdown Control. Drive
SHDN
low to enter low-power shutdown mode. Drive
SHDN
high or connect
to V
CC
for normal operation.
Overvoltage Indicator. Active low, open drain.
Ground
Negative Terminal of the Power Isolation Capacitor. Connect a 100V capacitor from C2- to C2+.
See Table 1 for values.
3.0V to 5.5V Supply Voltage. Bypass V
CC
to GND with a 1µF capacitor.
MAX3250
_______________________________________________________________________________________
5
