19-0162; Rev 2; 2/94
TION KIT
EVALUA INCLUDED
ATION
INFORM
+3V-Powered, Low-Power,
True RS-232 Transceiver
____________________________Features
SUPERIOR TO BIPOLAR:
o
Operates from Single +3.0V to +3.6V Supply
o
24-Pin SSOP or Wide SO Packages
o
Meets All EIA/TIA-232E & EIA/TIA-562
Specifications
o
3mA Max Supply Current (Unloaded)
o
1µA Low-Power Shutdown Mode
o
All Receivers Active During Low-Power Shutdown
o
Mouse Compatible at 3.0V
o
Low-Cost, Surface-Mount External Components
o
120kbps Guaranteed Data Rate—LapLink™
Compatible
o
Three-State Receiver Outputs
o
Evaluation Kit Available
o
Flow-Through Pinout
________________General Description
The MAX212 RS-232 transceiver is intended for 3V-pow-
ered EIA/TIA-232E and V.28/V.24 communication inter-
faces 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 main-
taining true RS-232 and EIA/TIA-562 voltage levels.
A 1µA typical shutdown mode reduces power con-
sumption, 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 compati-
bility with popular software for communicating with per-
sonal computers.
Three-state drivers on all receiver outputs are provided
so that multiple receivers, generally of different inter-
face 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.
MAX212
___________Typical Operating Circuit
23
+3.3V
V+
3 V
CC
1
LN
2
LP
14
V-
________________________Applications
Computers
Notebooks/Palmtops/Subnotebooks
Printers
Peripherals
Instruments
DC-DC CONVERTER
SHUTDOWN
4
SD
MAX212
T1
T1
OUT
17
11 T1
IN
_______________Ordering Information
12 T2
IN
T2
T2
OUT
16
PART
MAX212CWG
MAX212CAG
MAX212C/D
MAX212EWG
MAX212EAG
TEMP. RANGE
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
PIN-PACKAGE
24 Wide SO
24 SSOP
Dice*
24 Wide SO
24 SSOP
13 T3
IN
T3
T3
OUT
15
6 R1
OUT
R1
R1
IN
22
7 R2
OUT
R2
R2
IN
21
* Dice are tested at T
A
= +25°C only.
8 R3
OUT
R3
R3
IN
20
EV KIT
MAX212EVKIT-SSOP
TEMP. RANGE
0°C to +70°C
BOARD TYPE
Surface Mount
9 R4
OUT
R4
R4
IN
19
10 R5
OUT
R5
R5
IN
18
EN
ENABLE
5
GND
24
™LapLink is a registered trademark of Traveling Software.
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
+3V-Powered, Low-Power,
True RS-232 Transceiver
MAX212
ABSOLUTE MAXIMUM RATINGS
Supply Voltages
V
CC
.....................................................................-0.3V to +4.6V
V+ ............................................................(V
CC
- 0.3V) to +7.4V
V- ........................................................................-7.4V to +2.0V
LN ..............................................................-0.3V to (V+ + 1.0V)
LP.......................................................(V- - 1.0V) to (V+ + 0.3V)
Input Voltages
–
—
T_
IN
, SD, EN ..............................................-0.3V to (V+ + 0.3V)
R_
IN
...................................................................................±25V
Output Voltages
T_
OUT
................................................................................±15V
R_
OUT
........................................................-0.3V to (V+ + 0.3V)
Short-Circuit Duration, T_
OUT
.....................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
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
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 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
DC CHARACTERISTICS
Operating Voltage Range
V
CC
Supply Current
Shutdown Supply Current
Shutdown Supply Current with
Receivers Active
LOGIC
Input Logic Threshold Low
Input Logic Threshold High
Input Current High
Input Current Low
Hysteresis
Logic Output Voltage Low
Logic Output Voltage High
Logic Output Leakage Current
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
EIA/TIA-232E Input Resistance
EIA/TIA-232E TRANSMITTERS
Output Voltage Swing (V
HIGH
, V
LOW
)
Output Resistance
EIA/TIA-232E Short-Circuit Current
All transmitters loaded 3kΩ to GND
V
CC
= V- = V+ = 0V, -2V < T_
OUT
< 2V
±5.0
300
28
100
±5.5
V
Ω
mA
-15V < V
IN
< 15V
3
0.7
5
7
-25
0.4
2.8
+25
V
V
V
V
kΩ
–
—
T_
IN
, EN, SD; V
CC
= 3.0V to 3.6V
–
—
T_
IN
, EN, SD; V
CC
= 3.0V to 3.6V
–
—
T_
IN
, EN, SD; V
IN
= V
CC
–
—
T_
IN
, EN, SD, V
IN
= GND
T_
IN
; V
CC
= 3.3V
I
OUT
= 1.0mA
I
OUT
= -1.0mA
EN = GND, 0V < R_
OUT
< V
CC
V
CC
- 0.5
±10
V
CC
/ 3
2V
CC
/ 3
1
1
0.3
0.25
V
V
µA
µA
V
V
V
µA
Meets or exceeds EIA/TIA-232E specifications
No load, V
CC
= 3.3V
–
—
SD = EN = GND, R_
IN
= GND or V
CC
–
—
SD = GND, EN = V
CC
, R_
IN
= GND or V
CC
3.0
1.5
1
1
3.6
3.0
15
15
V
mA
µA
µA
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
+3V-Powered, Low-Power,
True RS-232 Transceiver
TIMING CHARACTERISTICS
(V
CC
= 3.0V to 3.6V, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Data Rate
Receiver Output Enable Time
Receiver Output Disable Time
Transmitter Output Enable Time
Transmitter Output Disable Time
Receiver Propagation Delay
Transmitter Propagation Delay
Transition-Region Slew Rate
t
ER
t
DR
t
ET
t
DT
t
PHLR
t
PLHR
t
PHLT
t
PLHT
150pF load
2500pF
3kΩ load
R
L
= 3kΩ to 7kΩ, C
L
= 50pF to 2500pF,
measured from +3V to -3V or -3V to +3V
4.0
Includes power-supply start-up
SYMBOL
CONDITIONS
1000pF
3kΩ load on each transmitter,
150pF load on each receiver
MIN
120
TYP
250
70
420
250
600
300
300
800
800
10
700
700
2000
2000
30
200
700
MAX
UNITS
kbps
ns
ns
µs
ns
ns
ns
V/µs
MAX212
__________________________________________Typical Operating Characteristics
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
SUPPLY POWER vs.
DATA RATE
212 GR4
TRANSMITTER OUTPUT VOLTAGE vs.
DATA RATE
212 GR5
180
160
SUPPLY POWER (mW)
140
120
100
ALL TRANSMITTERS
LOADED w/ 3kΩ AND
STATED CAPACITANCE
3 TRANSMITTERS
AT DATA RATE
3 TRANSMITTERS,
1 AT DATA RATE,
1 LOW, 1 HIGH
2500pF
6
4
OUTPUT VOLTAGE (V)
2
0
-2
-4
-6
5000pF
4000pF
2500pF
1000pF
ALL TRANSMITTERS
LOADED SIMULTANEOUSLY
w/ SPECIFIED CAPACITANCE AND 3kΩ
5000pF
4000pF
2500pF
1000pF
1000pF
2500pF
80
60
0
20
40
60
80
100
120
DATA RATE (kbps)
1000pF
0
50
100
150
200
250
DATA RATE (kbps)
_______________________________________________________________________________________
3
+3V-Powered, Low-Power,
True RS-232 Transceiver
MAX212
____________________________Typical Operating Characteristics (continued)
(V
CC
= 3.3V, T
A
= +25°C, unless otherwise noted.)
SUPPLY POWER vs.
SUPPLY VOLTAGE
212 GR2
SUPPLY CURRENT vs.
LOAD CAPACITANCE
212 GR3
SLEW RATE vs.
LOAD CAPACITANCE
13
12
SLEW RATE (V/µs)
11
10
9
8
FALLING EDGE
ALL TRANSMITTERS
LOADED SIMULTANEOUSLY
w/ SPECIFIED CAPACITANCE AND 3kΩ
500
1500
2500
3500
RISING EDGE
212 GR6
180
120kbps
160
SUPPLY POWER (mW)
ALL TRANSMITTERS
AT SPECIFIED DATA RATES
w/ 2500pF AND 3kΩ LOADS
80
70
SUPPLY CURRENT (mA)
60
50
64kbps
40
30
ALL TRANSMITTERS
AT SPECIFIED CAPACITANCE AND
DATA RATES w/ 3kΩ LOADS
120kbps
14
140
64kbps
120
100
20kbps
80
2.5
3.0
3.5
4.0
4.5
SUPPLY VOLTAGE (V)
20kbps
20
0
1000
2000
3000
4000
5000
LOAD CAPACITANCE (pF)
7
6
4500
LOAD CAPACITANCE (pF)
_____________________Pin Description
PIN
1
2
3
NAME
LN
LP
V
CC
FUNCTION
Inductor/Diode Connection Point
Inductor/Diode Connection Point
Supply Voltage Input, 3.0V to 3.6V
Shutdown Control. Connect to V
CC
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
to V
CC
for normal operation.
Connect to GND to force the
receiver outputs into a high-Z state.
Receiver Outputs, swing GND
to V
CC
Transmitter Inputs
Negative Supply generated on-board
Transmitter Outputs
Receiver Inputs
Positive Supply generated on-board
Ground
_______________Detailed Description
The MAX212 line driver/receiver is intended for 3V-
powered 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.
The circuit comprises three sections: power supply,
transmitters, and receivers. The power-supply sec-
tion converts the supplied 3V to about ±6.5V, to pro-
vide 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 oper-
ate 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 inter-
face standards, can be wire-ORed at the UART.
4
–
—
SD
5
EN
6-10
11-13
14
15-17
18-22
23
24
R1
OUT
-
R5
OUT
T1
IN
-T3
IN
V-
T3
OUT
-
T1
OUT
R5
IN
-R1
IN
V+
GND
4
_______________________________________________________________________________________
+3V-Powered, Low-Power,
True RS-232 Transceiver
Switch-Mode Power Supply
D1
1N6050
C1
0.68µF
+3.3V
C3
0.33µF
SHUTDOWN
4
SD
L
15µH
D2
1N6050
C2
0.33µF
V-
MAX212
23
V+
3 V
CC
1
LN
2
LP
+3.3V TO ±6.5V
DC-DC CONVERTER
14
MAX212
T1
T1
OUT
17
T2
OUT
16
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
least 350mA and under 1Ω resistance. Sample surface-
mount 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.
For C1 and C2, use ceramic capacitors with values no
less than indicated in Figure 1. These capacitors deter-
mine the ripple on V+ and V-, but not the absolute volt-
ages. Bypass V
CC
to GND with at least 0.33µF close to
the MAX212. Increase this to 4.7µF if there are no other
V
CC
supply bypass components less than 6 inches
(15cm) away from the MAX212.
Component suppliers are listed in Table 1.
11 T1
IN
12 T2
IN
T2
13 T3
IN
6 R1
OUT
T3
R1
T3
OUT
15
R1
IN
22
7 R2
OUT
R2
R2
IN
21
RS-232 Drivers
All three drivers are identical and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when V
CC
is
between 3.0V and 3.6V. Disable the drivers by taking
–
—
the SD pin to GND. The transmitter outputs are forced
–
—
into a high-impedance state when SD is grounded.
8 R3
OUT
R3
R3
IN
20
9 R4
OUT
R4
R4
IN
19
10 R5
OUT
R5
GND
24
R5
IN
18
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 V
CC
). When EN
–
—
is high, the receivers are active regardless of SD’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.
EN
5
ENABLE
Figure 1. Typical Application Circuit
Table 1. Suggested Component Suppliers
MANUFACTURER
Allegro
Motorola
Murata
Philips
Sumida
TDK
PART NUMBER
TMPD6050LT
MMBD6050LT1
LQH4N150K-TA
PMBD6050
CD43150
NLC453232T-150K
PHONE NUMBER
USA (508) 853-5000
USA (408) 749-0510
USA (404) 831-9172
Japan (075) 951-9111
USA (401) 762-3800
USA (708) 956-0666
Japan (03) 3607-5111
USA (708) 803-6100
Japan (03) 3278-5111
FAX NUMBER
USA (508) 853-5049
USA (408) 991-7420
USA (404) 436-3030
Japan (075) 955-6526
USA (401) 767-4493
USA (708) 956-0702
Japan (03) 3607-5428
USA (708) 803-6296
Japan (03) 3278-5358
_______________________________________________________________________________________
5
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