MAXIM MAX3250 User Manual

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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 trans­ceivers have a proprietary low-dropout transmitter out­put 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 exces­sive isolated-side voltage condition on any of the RS­232 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.

Applications

Industrial Control

Programmable Logic Controller

Point-of-Sale Equipment

PC-to-Router Connections

Diagnostic Ports

Telecom Equipment

Features

♦ ±50V Isolation

♦ 20µA Supply Current in Shutdown

♦ 250kbps Guaranteed Data Rate
♦ FAULT Output

♦ High-Impedance Transmitter and Receiver

Outputs in Shutdown

♦ Space-Saving SSOP Package

♦ Inductorless/Transformerless Design Simplifies

EMI Compliance

♦ Low-Cost Replacement for Opto-Isolated

Transceivers

♦ Meets EIA/TIA-232 Specifications Down to 3.0V

MAX3250

±50V Isolated, 3.0V to 5.5V,

250kbps, 2 Tx/2 Rx, RS-232 Transceiver

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-2443; Rev 1; 2/03

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.

Typical Operating Circuit appears at end of data sheet.

Pin Configuration

PART TEMP RANGE PIN-PACKAGE

MAX3250CAI 0°C to +70°C 28 SSOP

MAX3250EAI -40°C to +85°C 28 SSOP

TOP VIEW

C1-

R1OUT

R2OUT

T1IN

T2IN

N.C.

N.C.

C1+

C3+

C3-

C4+

C4-

1

2

3

4

5

MAX3250

6

7

8

9

10

V+

11

12

13

14

V-

SSOP

28

27

26

25

24

23

22

21

20

19

18

17

16

15

V

CC

C2-

GND

FAULT

SHDN

N.C.

N.C.

C2+

ISOV

CC

R1IN

R2IN

T1OUT

T2OUT

ISOCOM

MAX3250

±50V Isolated, 3.0V to 5.5V,
250kbps, 2 TX/2 RX, RS-232 Transceiver

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

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

ELECTRICAL CHARACTERISTICS

(VCC= 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA= T

MIN

to T

MAX

, unless oth-

erwise noted. Typical values are at V

CC

= 3.3V and TA= +25°C.) (Note 2)

Note 1: V+ and V- can have a maximum magnitude of 7V, but their absolute difference cannot exceed 13V.

DC CHARACTERISTICS

Supply Current SHDN = VCC, no load 15 35 mA

Supply Current Shutdown

Maximum Ground Differential |V

Isolation Resistance Between GND and ISOCOM 60 kΩ

LOGIC INPUTS

Input Logic Low T_IN, SHDN 0.8 V

Input Logic High T_IN, SHDN

Transmitter Input Hysteresis 0.5 V
Input Leakage Current T_IN, SHDN -1 ±0.01 +1 µA

RECEIVER OUTPUTS

Output Leakage Current SHDN = GND -10 ±0.05 +10 µA

Output Voltage Low I

PARAMETER CONDITIONS MIN TYP MAX UNITS

SHDN = GND, V
SHDN = GND, V

- V

GND

ISOCOM

= 1.6mA 0.4 V

OUT

= GND 20 45

ISOCOM

= ±50V ±350

ISOCOM

| 50 V

V

= 3.3V 2.0

CC

V

= 5.0V 2.4

CC

µA

V

Output Voltage High I

FAULT OUTPUT

Output Voltage Low
(Open Drain)

Output Leakage Current FAULT not asserted 1 µA
FAULT Trip Level |V

= -1.0mA V

OUT

I

= 5mA 0.4 V

OUT

GND

- V

| 55 V

ISOCOM

CC

- 0.6 V

- 0.1 V

CC

MAX3250

±50V Isolated, 3.0V to 5.5V,

250kbps, 2 TX/2 RX, RS-232 Transceiver

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VCC= 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA= T

MIN

to T

MAX

, unless oth-

erwise noted. Typical values are at V

CC

= 3.3V and TA= +25°C.) (Note 2)

PARAMETER CONDITIONS

UNITS

RECEIVER INPUTS (relative to ISOCOM)

Input Voltage Range -25

V

V

CC

= 3.3V 1.2 0.6

Input Threshold Low TA = +25°C

V

CC

= 5.0V 1.3 0.8

V

V

CC

= 3.3V 2.4 1.6

Input Threshold High TA = +25°C

V

CC

= 5.0V 2.4 1.7

V

Input Hysteresis 0.5 V

Input Resistance TA = +25°C 357kΩ

TRANSMITTER OUTPUTS (relative to ISOCOM)

Output Voltage Swing All transmitter outputs loaded with 3kΩ to ISOCOM

V

Output Resistance ISOVCC = V+ = V- = 0V, T_OUT = ±2V

Ω

Output Short-Circuit Current -60

mA

Output Leakage Current VCC = 0 or 3V to 5.5V, T_OUT = ±12V, SHDN = GND -25

µA

TIMING CHARACTERISTICS

(VCC= 3.0V to 5.5V, see Typical Operating Circuit and Table 1 for capacitor values, ISOCOM = GND, TA= T

MIN

to T

MAX

, unless oth-

erwise noted. Typical values are at V

CC

= 3.3V and TA= +25°C.)

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.

MIN TYP MAX

±5.0 ±5.4

300 10M

+25

+60

+25

Maximum Data Rate

Receiver Propagation Delay R_IN to R_OUT, CL = 150pF to GND 0.4 µs

Receiver Skew |t

Transmitter Skew |t

Transition-Region Slew Rate

FAULT Propagation Delay 0.3 µs

Time to Shutdown 0.5 µs

Time to Exit Shutdown

PARAMETER CONDITIONS MIN TYP MAX UNITS

= 3kΩ, CL = 1000pF to ISOCOM, one transmitter

R

L

- t

PHL

PHL

V

CC

= 3kΩ to 7kΩ to ISOCOM,

R

L

measured from +3V to -3V or

-3V to +3V

V

ISOCOM

V

ISOCOM

| 100 ns

PLH

- t

| (Note 3) 120 ns

PLH

= 3.3V, TA = +25°C,

= GND 300

= ±50V 350

CL = 150pF to 1000pF
to ISOCOM

C

= 150pF to 2500pF

L

to ISOCOM

250 kbps

630

430

V/µs

µs