MAXIM MAX212 User Manual

19-0162; Rev 2; 2/94

EVALUATION KIT

INFORMATION INCLUDED

+3V-Powered, Low-Power,

True RS-232 Transceiver

________________General Description

The MAX212 RS-232 transceiver is intended for 3V-pow­ered EIA/TIA-232E and V.28/V.24 communication inter­faces where 3 drivers and 5 receivers are needed with
minimum power consumption. The operating voltage
range extends from 3.6V down to 3.0V while still main­taining true RS-232 and EIA/TIA-562 voltage levels.

A 1µA typical shutdown mode reduces power con­sumption, extending battery life in portable systems.
While shut down, all receivers can remain active or can
be disabled under logic control. This enables a system
incorporating the CMOS MAX212 to be in low-power
shutdown mode and monitor incoming RS-232 activity.

A guaranteed data rate of 120kbps provides compati­bility with popular software for communicating with per­sonal computers.

Three-state drivers on all receiver outputs are provided
so that multiple receivers, generally of different inter­face standards, can be wire-ORed at the UART.

The MAX212 is available in both small-outline (SO) and
shrink-small-outline (SSOP) packages. The SSOP
package occupies less than half of the board area
required by the equivalent SO package.

________________________Applications

Computers

Notebooks/Palmtops/Subnotebooks
Printers
Peripherals
Instruments

_______________Ordering Information

PART TEMP. RANGE PIN-PACKAGE

MAX212CWG 0°C to +70°C 24 Wide SO
MAX212CAG 0°C to +70°C 24 SSOP
MAX212C/D 0°C to +70°C Dice*
MAX212EWG -40°C to +85°C 24 Wide SO
MAX212EAG -40°C to +85°C 24 SSOP

* Dice are tested at TA= +25°C only.

____________________________Features

SUPERIOR TO BIPOLAR:

♦ Operates from Single +3.0V to +3.6V Supply
♦ 24-Pin SSOP or Wide SO Packages
♦ Meets All EIA/TIA-232E & EIA/TIA-562

Specifications

♦ 3mA Max Supply Current (Unloaded)
♦ 1µA Low-Power Shutdown Mode
♦ All Receivers Active During Low-Power Shutdown
♦ Mouse Compatible at 3.0V
♦ Low-Cost, Surface-Mount External Components
♦ 120kbps Guaranteed Data Rate—LapLink™

Compatible

♦ Three-State Receiver Outputs
♦ Evaluation Kit Available
♦ Flow-Through Pinout

___________T ypical Operating Circuit

+3.3V

SHUTDOWN

1

LN

3

V

CC

DC-DC CONVERTER

4

SD

T1

11

IN

T2

12 16

IN

T3

13 15

IN

R1

622

OUT

R2

721

OUT

R3

820

OUT



MAX212

T1

T2

T3

21423

LP V-V+

T1

17

OUT

T2

OUT

T3

OUT

R1

IN

R1

R2

IN

R2

R3

IN

R3

MAX212

EV KIT TEMP. RANGE BOARD TYPE

R4

919

OUT

MAX212EVKIT-SSOP 0°C to +70°C Surface Mount

R5

10 18

OUT

EN

5

™LapLink is a registered trademark of Traveling Software.

ENABLE

________________________________________________________________

Call toll free 1-800-998-8800 for free samples or literature.

R4

IN

R4

R5

IN

R5

GND

24

Maxim Integrated Products

1

+3V-Powered, Low-Power,
True RS-232 Transceiver

ABSOLUTE MAXIMUM RATINGS

Supply Voltages

.....................................................................-0.3V to +4.6V

V

CC

V+............................................................(V

V-........................................................................-7.4V to +2.0V

LN..............................................................-0.3V to (V+ + 1.0V)

LP.......................................................(V- - 1.0V) to (V+ + 0.3V)

Input Voltages

MAX212

, –S—D, EN..............................................-0.3V to (V+ + 0.3V)

T_

IN

...................................................................................±25V

R_

IN

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.

- 0.3V) to +7.4V

CC

Output Voltages

T_

................................................................................±15V

OUT

........................................................-0.3V to (V+ + 0.3V)

R_

OUT

Short-Circuit Duration, T_
Continuous Power Dissipation (T

Wide SO (derate 11.76mW/°C above +70°C)...............941mW

SSOP (derate 8.00mW/°C above +70°C) .....................640mW

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

.....................................Continuous

OUT

= +70°C)

A

ELECTRICAL CHARACTERISTICS

(VCC= 3.0V to 3.6V, TA= T

PARAMETER MIN TYP MAX UNITS

DC CHARACTERISTICS

Operating Voltage Range 3.0 3.6 V
VCCSupply Current 1.5 3.0 mA

Shutdown Supply Current 115µA
Shutdown Supply Current with

Receivers Active

LOGIC

Input Logic Threshold Low V
Input Logic Threshold High 2V
Input Current High 1 µA
Input Current Low 1 µA
Hysteresis 0.3 V
Logic Output Voltage Low 0.25 V
Logic Output Voltage High V
Logic Output Leakage Current ±10 µA

EIA/TIA-232E RECEIVERS

EIA/TIA-232E Input Voltage
Operating Range

EIA/TIA-232E Input Voltage
Threshold Low

EIA/TIA-232E Input Voltage
Threshold High

EIA/TIA-232E Input Hysteresis 0.7 V
EIA/TIA-232E Input Resistance 357kΩ

EIA/TIA-232E TRANSMITTERS

Output Voltage Swing (V
Output Resistance 300 Ω
EIA/TIA-232E Short-Circuit Current

MIN

HIGH

to T

, unless otherwise noted.)

MAX

Meets or exceeds EIA/TIA-232E specifications
No load, VCC= 3.3V

–S—

D= EN = GND, R_

–S—

D = GND, EN = V

T_IN, EN, –S—D; VCC= 3.0V to 3.6V
T_IN, EN, –S—D; VCC= 3.0V to 3.6V
T_IN, EN, –S—D; VIN= V
T_IN, EN, –S—D, VIN= GND
T_IN; V
I

OUT

I

OUT

EN = GND, 0V < R_

-15V < VIN< 15V

, V

All transmitters loaded 3kΩ to GND

)

LOW

VCC= V- = V+ = 0V, -2V < T_

= 3.3V

CC

= 1.0mA
= -1.0mA

CONDITIONS

= GND or V

IN

, R_IN= GND or V

CC

CC

< V

OUT

CC

OUT

CC

< 2V

CC

115µA

/ 3 V

CC

/ 3 V

CC

- 0.5 V

CC

-25 +25 V

0.4 V

2.8 V

±5.0 ±5.5 V

28 100 mA

2 _______________________________________________________________________________________

+3V-Powered, Low-Power,

True RS-232 Transceiver

TIMING CHARACTERISTICS

(VCC= 3.0V to 3.6V, TA= T

PARAMETER MIN TYP MAX UNITS

Data Rate 120 250 kbps
Receiver Output Enable Time 70 200 ns

Receiver Output Disable Time 420 700 ns

Transmitter Output Enable Time
Transmitter Output Disable Time 600 ns

Receiver Propagation Delay

Transmitter Propagation Delay

Transition-Region Slew Rate

MIN

to T

, unless otherwise noted.)

MAX

SYMBOL

t

ER

t

DR

t

ET

t

DT

t

PHLR

t

PLHR

t

PHLT

t

PLHT

CONDITIONS

1000pF  3kΩ load on each transmitter,
150pF load on each receiver

Includes power-supply start-up

2500pF 3kΩ load

RL= 3kΩ to 7kΩ, CL= 50pF to 2500pF,
measured from +3V to -3V or -3V to +3V

250 µs

300 700
300 700
800 2000
800 2000

ns150pF load

ns

4.0 10 30 V/µs

__________________________________________Typical Operating Characteristics

(VCC= 3.3V, TA = +25°C, unless otherwise noted.)

SUPPLY POWER vs.

180

ALL TRANSMITTERS
LOADED w/ 3kΩ AND

160

STATED CAPACITANCE
3 TRANSMITTERS

140

AT DATA RATE
3 TRANSMITTERS,

120

1 AT DATA RATE,
1 LOW, 1 HIGH

100

SUPPLY POWER (mW)

80

60

0204060

DATA RATE

DATA RATE (kbps)

212 GR4

2500pF

1000pF

2500pF

1000pF

120

100

80

TRANSMITTER OUTPUT VOLTAGE vs.

DATA RATE

6

4

2

0

-2

OUTPUT VOLTAGE (V)

-4

-6
0 50 100 150

5000pF

ALL TRANSMITTERS
LOADED SIMULTANEOUSLY
w/ SPECIFIED CAPACITANCE AND 3kΩ

5000pF
4000pF
2500pF
1000pF

DATA RATE (kbps)

4000pF
2500pF
1000pF

200

212 GR5

250

MAX212

_______________________________________________________________________________________ 3

+3V-Powered, Low-Power,
True RS-232 Transceiver

____________________________Typical Operating Characteristics (continued)

(VCC= 3.3V, TA = +25°C, unless otherwise noted.)

SUPPLY POWER vs.

180

MAX212

160

140

120

SUPPLY POWER (mW)

100

80

2.5 3.0 3.5 4.0

SUPPLY VOLTAGE

ALL TRANSMITTERS
AT SPECIFIED DATA RATES
w/ 2500pF AND 3kΩ LOADS

SUPPLY VOLTAGE (V)

120kbps

64kbps

20kbps

212 GR2

4.5

80

70

60

50

40

SUPPLY CURRENT (mA)

30

20

0 1000 2000 3000

_____________________Pin Description

PIN

6-10

11-13

15-17

18-22

NAME FUNCTION

1
2
3

LN
LP

V

CC

Inductor/Diode Connection Point
Inductor/Diode Connection Point
Supply Voltage Input, 3.0V to 3.6V
Shutdown Control. Connect to V

4

–S—

D

for normal operation. Connect to
GND to shut down the power supply
and to disable the drivers. Receiver
status is not changed by this control.

Receiver Enable Control. Connect

5

EN

to VCCfor normal operation.
Connect to GND to force the
receiver outputs into a high-Z state.

R1

-

OUT

R5

OUT

T1IN-T3

V-14

T3

OUT

T1

OUT

R5IN-R1

Receiver Outputs, swing GND
to V

Transmitter Inputs

IN

Negative Supply generated on-board

­Transmitter Outputs

Receiver Inputs

IN

V+ Positive Supply generated on-board23

GND Ground24

CC

SUPPLY CURRENT vs.

LOAD CAPACITANCE

ALL TRANSMITTERS
AT SPECIFIED CAPACITANCE AND
DATA RATES w/ 3kΩ LOADS

LOAD CAPACITANCE (pF)

_______________Detailed Description

The MAX212 line driver/receiver is intended for 3V­powered EIA/TIA-232E and V.28/V.24 communications
interfaces where 3 drivers and 5 receivers are
required. The operating voltage range extends from

3.6V down to 3.0V while still maintaining true RS-232
and EIA/TIA-562 transmitter output voltage levels.

CC

The circuit comprises three sections: power supply,
transmitters, and receivers. The power-supply sec­tion converts the supplied 3V to about ±6.5V, to pro­vide the voltages necessary for the drivers to meet
true RS-232 levels. External components are small
and inexpensive.

The transmitters and receivers are guaranteed to oper­ate at data rates of 120kbps.

A shutdown mode reduces current to 1µA to extend
battery life in portable systems. While shut down, all
receivers can remain active or can be disabled under
logic control. This enables a system incorporating the
MAX212 to be in low-power shutdown mode and still
monitor incoming RS-232 activity.

Three-state drivers on all receiver outputs are provided
so that multiple receivers, generally of different inter­face standards, can be wire-ORed at the UART.

120kbps

64kbps

20kbps

4000

5000

14

212 GR3

13

12
11

10

9

SLEW RATE (V/µs)

ALL TRANSMITTERS

8

LOADED SIMULTANEOUSLY
w/ SPECIFIED CAPACITANCE AND 3kΩ

7
6

500 1500 2500 3500

SLEW RATE vs.

LOAD CAPACITANCE

RISING EDGE

FALLING EDGE

LOAD CAPACITANCE (pF)

4500

212 GR6



4 _______________________________________________________________________________________

+3V-Powered, Low-Power,

True RS-232 Transceiver

D1

1N6050

15µH

0.33µF

SHUTDOWN

ENABLE

0.68µF

+3.3V

C3

C1

1

LN

3

V

CC

+3.3V TO ±6.5V

DC-DC CONVERTER

4

11

12 16

13 15

622

721

820

919

10 18

MAX212

SD

T1

IN

T2

IN

T3

IN

R1

OUT

R2

OUT

R3

OUT

R4

OUT

R5

OUT

EN

GND

24

5

Figure 1. Typical Application Circuit

L

D2

1N6050

C2

21423

LP V-V+

0.33µF

The switch-mode power supply uses a single inductor
with two inexpensive diodes and two capacitors to
generate ±6.5V from the 3.0V to 3.6V input. Figure 1
shows the complete circuit for the power supply.

Use a 15µH inductor with a saturation current rating of at

Switch-Mode Power Supply

MAX212

least 350mA and under 1Ω resistance. Sample surface­mount inductors are available from Maxim. Use 1N6050
diodes or equivalent. Surface-mount equivalents for the
1N6050 include the Motorola MMBD6050LT1, Philips
PMBD6050, and Allegro (formerly Sprague) TMPD6050LT.

T1

17

T1

T2

T3

OUT

T2

OUT

T3

OUT

R1

R1

R2

R3

R4

R5

IN

R2

IN

R3

IN

R4

IN

R5

IN

For C1 and C2, use ceramic capacitors with values no
less than indicated in Figure 1. These capacitors deter­mine the ripple on V+ and V-, but not the absolute volt­ages. Bypass VCCto GND with at least 0.33µF close to
the MAX212. Increase this to 4.7µF if there are no other
VCCsupply bypass components less than 6 inches
(15cm) away from the MAX212.

Component suppliers are listed in Table 1.

RS-232 Drivers

All three drivers are identical and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when VCCis
between 3.0V and 3.6V. Disable the drivers by taking
the –S—Dpin to GND. The transmitter outputs are forced
into a high-impedance state when –S—D is grounded.

RS-232 Receivers

All five receivers are identical and accept
EIA/TIA-232E and EIA/TIA-562 input signals. The CMOS
receiver outputs swing rail-to-rail (0V to VCC). When EN
is high, the receivers are active regardless of –S—D’s status.
When EN is low, the receivers’ outputs are put into a
high-impedance state. This allows two RS-232 ports (or
two parts of different types) to be wire-ORed at the UART.

Table 1. Suggested Component Suppliers

MANUFACTURER PART NUMBER PHONE NUMBER FAX NUMBER

Allegro TMPD6050LT USA [phone]
Motorola MMBD6050LT1 USA [phone]

Murata LQH4N150K-TA
Philips PMBD6050 USA [phone] USA [phone]
Sumida CD43150

TDK NLC453232T-150K

_______________________________________________________________________________________ 5

USA [phone]
USA [phone]

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

USA [phone]
Japan [phone]

+3V-Powered, Low-Power,
True RS-232 Transceiver

–S—

D and EN determine the operation of the MAX212

Operating Modes

as follows:

–S—

D

L L High-Z High-Z Off Minimum

MAX212

L H Enabled High-Z Off Minimum
H L High-Z Enabled On Normal
H H Enabled Enabled On Normal

EN

RECEIVER

OUTPUTS

DRIVER

OUTPUTS

DC-DC

CONVERTER

SUPPLY

CURRENT

Shutdown

V+ and V- are disabled and the transmitters are put into
a high-impedance state when –S—Dis taken to logic low.
Receiver operation is not affected, but power consump­tion is dramatically reduced while in shutdown mode.
Supply current is minimized when the receiver inputs are
static in any of three states: floating (ground), less than
GND, or greater than VCC. This will be true for all static
RS-232 conditions. The presence of AC signals on receiv­er inputs will increase VCCcurrent in shutdown.

From a low-power system perspective, powering-up with
non-critical or unused sections of circuitry shut down or
deselected is generally recommended. Activating these
sections only when required saves power and reduces
power-up current surges. Powering-up the MAX212 in
shutdown mode (holding the shutdown pin,

–S—

D, low until VCC> 2.7V), helps to achieve this.

Driving the MAX212 from 5V Logic

The MAX212 can interface with 5V logic while it operates
from a 3V supply, however a 200kΩseries resistor between

–S—

D and the +5V logic signal is required (see Figure 2).
This protects the MAX212 by preventing –S—Dfrom sinking
current while V+ is powering up. Also, the UART must not
be permitted to send a logic high to the MAX212’s EN or
transmitter input pins until –S—Dis high (not shut down).

LN

200k

V+

DC-DC CONVERTER

SD

T_

IN

R_

OUT

+3.3V

+5V

LOGIC

SIGNALS

Figure 2. Connecting to +5V Logic

MAX212

EN

LP V-

T

X

X3

R

X

X5

GND

T_

OUT

R_

IN

Mouse Driveability

The MAX212 has been specifically designed to power
serial mice while operating from low-voltage power
supplies. It has been tested with samples of ten major
mouse models from six manufacturers, including the
leading three, Logitech (5 models), Mouse Systems,
and Microsoft. The MAX212 successfully drove all seri­al mice and met their respective current and voltage
requirements (Figure 1).

Figure 3 shows the transmitter output voltages under
increasing load current. The MAX212’s switching regu­lator ensures the transmitters will supply at least ±5V
during worst-case load conditions.

EIA/TIA-232E and 562 Standards

Most of the power drawn by RS-232 circuits is con­sumed because the EIA/TIA-232E standard demands
that at least ±5V be delivered by the transmitters to
impedances that can be as low as 3kΩ. For applica-

____________________________+3V Powered RS-232 Transceivers from Maxim

PART

MAX212 3.0 to 3.6 3/5 5 250 True RS-232 from +3V
MAX560 3.0 to 3.6 4/5 2 120 2 receivers active in shutdown
MAX561 3.0 to 3.6 4/5 0 120 Pin compatible with MAX241
MAX562 2.7 to 5.25 3/5 5 250 Wide supply range

6 _______________________________________________________________________________________

POWER-SUPPLY

VOLTAGE

(V)

No. OF

TRANSMITTERS/

RECEIVERS

No. OF

RECEIVERS

ACTIVE IN

SHUTDOWN

DATA RATE

(kbps)

FEATURES

+3V-Powered, Low-Power,

True RS-232 Transceiver

TRANSMITTER OUTPUT VOLTAGE vs.

LOAD CURRENT PER TRANSMITTER

6

T1

AND T2

OUT

IN

, T1

= GND,

OUT

OUT



T3

OUT

5 6

4

T1IN AND T2

2

= VCC = 3.0V,

T3

IN

, T2

T3

OUT

OUT

ALL LOADED

0

SIMULTANEOUSLY

-2

-4

TRANSMITTER OUTPUT VOLTAGE (V)

-6
1234

LOAD CURRENT PER TRANSMITTER (mA)

Figure 3. Mouse Emulation Circuit Current

212 GR1

tions where power consumption is especially critical,
the EIA/TIA-562 standard provides an alternative.

EIA/TIA-562 transmitter output voltage levels need only
reach ±3.7V, and because they need only drive the
same 3kΩ receiver loads specified by RS-232, total
power consumption is considerably reduced. Since the
EIA/TIA-232E and EIA/TIA-562 receiver input voltage
thresholds are the same, interoperability between the two
standards is guaranteed and devices from both stan­dards will communicate with each other successfully.

Maxim’s MAX560 and MAX561 are EIA/TIA-562 trans­ceivers that operate on a single supply from 3.0V to

3.6V, and the MAX562 transceiver operates from 2.7V
to 5.25V while producing EIA/TIA-562 levels.

______________________Evaluation Kit

The MAX212 evaluation kit (EV kit) is a fully assem­bled and tested, surface-mount demonstration board
that provides quick and easy evaluation of the
MAX212.

The MAX212 EV kit is intended for 3.3V ±300mV-pow­ered EIA/TIA-232E and V.28/V.24 communications
interfaces where 3 drivers and 5 receivers are needed
with minimum power consumption.

A logic or pin-selectable shutdown mode reduces
current to 1µA. While shut down, all receivers can
remain active or can be disabled under logic control
via the EN input.

MAX212

Figure 4. MAX212 Evaluation Kit

_______________________________________________________________________________________ 7

+3V-Powered, Low-Power,
True RS-232 Transceiver

_________________Pin Configuration

TOP VIEW

MAX212

LN
LP

V

CC

SD
EN

R1

OUT

R2

OUT

R3

OUT

R4

OUT

R5

OUT

T1

IN

T2

IN

1
2
3
4

MAX212

5
6
7
8

9
10
11
12

SSOP/WIDE SO

GND

24

V+

23

R1

22

IN

R2

21

IN

R3

20

IN

R4

19

IN

R5

18

IN

T1

17

OUT

T2

16

OUT

T3

15

OUT

V-

14

T3

13

IN

___________________Chip Topography

LP GND

IN

T2

T3

IN

IN

0.1"

(2.54mm)

GNDLN

V+

R1

IN

R2

IN

R3

IN

R4

IN

R5

IN

0.15"

(3.81mm)

T1

OUT

T2

OUT

T3

OUT

V-

V

CC

V

CC

SD
EN

R1

OUT

R2

OUT

R3

OUT

R4

OUT

R5

OUT

T1

TRANSISTOR COUNT: 1382 ;
SUBSTRATE CONNECTED TO V+.

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 [phone]

© 1993 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.