19-0162; Rev 2; 2/94
TION KIT
EVALUA INCLUDED
N
IO
T
A
INFORM
+3V-Powered, Low-Power,
True RS-232 Transceiver
____________________________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
___________Typical Operating Circuit
________________________Applications
Computers
Notebooks/Palmtops/Subnotebooks
Printers
Peripherals
Instruments
23
+3.3V
V+
3 V
CC
1
LN
2
14
LP
V-
DC-DC CONVERTER
SHUTDOWN
4
MAX212
SD
11 T1IN
T1OUT 17
T1
_______________Ordering Information
12 T2IN
PART
TEMP. RANGE
PIN-PACKAGE
MAX212CWG
0°C to +70°C
24 Wide SO
MAX212CAG
MAX212C/D
MAX212EWG
MAX212EAG
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
24 SSOP
Dice*
24 Wide SO
24 SSOP
T2OUT 16
T2
13 T3IN
T3OUT 15
T3
6 R1OUT
R1
7 R2OUT
R2
R1IN 22
R2IN 21
* Dice are tested at TA = +25°C only.
8 R3OUT
EV KIT
TEMP. RANGE
BOARD TYPE
MAX212EVKIT-SSOP
0°C to +70°C
Surface Mount
R3
9 R4OUT
R4
10 R5OUT
R5
EN
ENABLE
5
R3IN 20
R4IN 19
R5IN 18
GND
24
™LapLink is a registered trademark of Traveling Software.
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
1
MAX212
________________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.
MAX212
+3V-Powered, Low-Power,
True RS-232 Transceiver
ABSOLUTE MAXIMUM RATINGS
Supply Voltages
VCC .....................................................................-0.3V to +4.6V
V+ ............................................................(VCC - 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 (TA = +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
(VCC = 3.0V to 3.6V, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC CHARACTERISTICS
Operating Voltage Range
Meets or exceeds EIA/TIA-232E specifications
VCC Supply Current
No load, VCC = 3.3V
–—
SD = EN = GND, R_IN = GND or VCC
Shutdown Supply Current
Shutdown Supply Current with
Receivers Active
3.0
–—
SD = GND, EN = VCC, R_IN = GND or VCC
3.6
V
1.5
3.0
mA
1
15
µA
1
15
µA
VCC / 3
V
1
µA
1
µA
LOGIC
Input Current Low
–—
T_IN, EN, SD; VCC = 3.0V to 3.6V
–—
T_IN, EN, SD; VCC = 3.0V to 3.6V
–—
T_IN, EN, SD; VIN = VCC
–—
T_IN, EN, SD, VIN = GND
Hysteresis
T_IN; VCC = 3.3V
Logic Output Voltage Low
IOUT = 1.0mA
Logic Output Voltage High
IOUT = -1.0mA
Logic Output Leakage Current
EN = GND, 0V < R_OUT < VCC
Input Logic Threshold Low
Input Logic Threshold High
Input Current High
2VCC / 3
V
0.3
V
0.25
V
±10
µA
+25
V
VCC - 0.5
V
EIA/TIA-232E RECEIVERS
EIA/TIA-232E Input Voltage
Operating Range
-25
EIA/TIA-232E Input Voltage
Threshold Low
0.4
V
EIA/TIA-232E Input Voltage
Threshold High
EIA/TIA-232E Input Hysteresis
EIA/TIA-232E Input Resistance
2.8
V
7
kΩ
0.7
-15V < VIN < 15V
3
5
±5.5
V
EIA/TIA-232E TRANSMITTERS
Output Voltage Swing (VHIGH, VLOW)
All transmitters loaded 3kΩ to GND
±5.0
Output Resistance
VCC = V- = V+ = 0V, -2V < T_OUT < 2V
300
EIA/TIA-232E Short-Circuit Current
2
V
Ω
28
_______________________________________________________________________________________
100
mA
+3V-Powered, Low-Power,
True RS-232 Transceiver
MAX212
TIMING CHARACTERISTICS
(VCC = 3.0V to 3.6V, TA = TMIN to TMAX, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
1000pF 3kΩ load on each transmitter,
150pF load on each receiver
Data Rate
MIN
TYP
120
250
MAX
UNITS
kbps
Receiver Output Enable Time
tER
70
200
ns
Receiver Output Disable Time
tDR
420
700
ns
Transmitter Output Enable Time
tET
Transmitter Output Disable Time
tDT
600
tPHLR
300
700
300
700
800
2000
800
2000
10
30
Receiver Propagation Delay
Includes power-supply start-up
tPLHR
tPHLT
Transmitter Propagation Delay
tPLHT
250
150pF load
2500pF 3kΩ load
RL = 3kΩ to 7kΩ, CL = 50pF to 2500pF,
measured from +3V to -3V or -3V to +3V
Transition-Region Slew Rate
4.0
µs
ns
ns
ns
V/µs
__________________________________________Typical Operating Characteristics
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
SUPPLY POWER vs.
DATA RATE
2500pF
3 TRANSMITTERS,
1 AT DATA RATE,
1 LOW, 1 HIGH
1000pF
5000pF
4
100
2500pF
80
1000pF
60
212 GR5
140
3 TRANSMITTERS
AT DATA RATE
120
6
212 GR4
160
ALL TRANSMITTERS
LOADED w/ 3kΩ AND
STATED CAPACITANCE
OUTPUT VOLTAGE (V)
SUPPLY POWER (mW)
180
TRANSMITTER OUTPUT VOLTAGE vs.
DATA RATE
2
4000pF
2500pF
1000pF
ALL TRANSMITTERS
LOADED SIMULTANEOUSLY
w/ SPECIFIED CAPACITANCE AND 3kΩ
0
-2
5000pF
4000pF
2500pF
1000pF
-4
-6
0
20
40
60
80
DATA RATE (kbps)
100
120
0
50
100
150
200
250
DATA RATE (kbps)
_______________________________________________________________________________________
3
____________________________Typical Operating Characteristics (continued)
(VCC = 3.3V, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs.
LOAD CAPACITANCE
160
ALL TRANSMITTERS
AT SPECIFIED CAPACITANCE AND
DATA RATES w/ 3kΩ LOADS
70
SUPPLY CURRENT (mA)
ALL TRANSMITTERS
AT SPECIFIED DATA RATES
w/ 2500pF AND 3kΩ LOADS
140
64kbps
120
100
120kbps
60
50
64kbps
40
20kbps
20kbps
20
2.5
3.0
3.5
4.0
4.5
0
1000
4
PIN
NAME
1
LN
Inductor/Diode Connection Point
2
LP
Inductor/Diode Connection Point
3
VCC
Supply Voltage Input, 3.0V to 3.6V
4
–—
SD
Shutdown Control. Connect to VCC
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.
5
EN
Receiver Enable Control. Connect
to VCC for normal operation.
Connect to GND to force the
receiver outputs into a high-Z state.
6-10
R1OUTR5OUT
11-13
T1IN-T3IN
14
V-
15-17
T3OUTT1OUT
18-22
R5IN-R1IN
V+
GND
2000
3000
4000
LOAD CAPACITANCE (pF)
_____________________Pin Description
24
12
11
10
FALLING EDGE
9
7
ALL TRANSMITTERS
LOADED SIMULTANEOUSLY
w/ SPECIFIED CAPACITANCE AND 3kΩ
6
SUPPLY VOLTAGE (V)
23
RISING EDGE
13
8
30
80
14
212 GR6
80
212 GR3
120kbps
212 GR2
180
SLEW RATE vs.
LOAD CAPACITANCE
SLEW RATE (V/µs)
SUPPLY POWER vs.
SUPPLY VOLTAGE
SUPPLY POWER (mW)
MAX212
+3V-Powered, Low-Power,
True RS-232 Transceiver
FUNCTION
Receiver Outputs, swing GND
to VCC
Transmitter Inputs
Negative Supply generated on-board
Transmitter Outputs
Receiver Inputs
5000
500
1500
2500
3500
4500
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.
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.
Positive Supply generated on-board
Ground
_______________________________________________________________________________________
+3V-Powered, Low-Power,
True RS-232 Transceiver
C1
0.68µF
+3.3V
23
1
4
D2
1N6050
2
LN
V+
3 V
CC
C2
0.33µF
14
LP
V-
+3.3V TO ±6.5V
DC-DC CONVERTER
C3
0.33µF
SHUTDOWN
L
15µH
MAX212
SD
11 T1IN
T1OUT 17
T1
12 T2IN
T2
13 T3IN
T3
6 R1OUT
T2OUT 16
T3OUT 15
R1IN 22
R1
7 R2OUT
R2IN 21
R2
8 R3OUT
R3IN 20
R3
9 R4OUT
R4IN 19
R4
10 R5OUT
R5IN 18
R5
EN
5
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 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.
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 VCC to GND with at least 0.33µF close to
the MAX212. Increase this to 4.7µF if there are no other
VCC supply bypass components less than 6 inches
(15cm) away from the MAX212.
Component suppliers are listed in Table 1.
GND
24
ENABLE
Figure 1. Typical Application Circuit
RS-232 Drivers
All three drivers are identical and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when VCC 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.
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 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.
Table 1. Suggested Component Suppliers
MANUFACTURER
PART NUMBER
PHONE NUMBER
FAX NUMBER
Allegro
TMPD6050LT
USA (508) 853-5000
USA (508) 853-5049
Motorola
MMBD6050LT1
USA (408) 749-0510
USA (408) 991-7420
Murata
LQH4N150K-TA
USA (404) 831-9172
Japan (075) 951-9111
USA (404) 436-3030
Japan (075) 955-6526
Philips
PMBD6050
USA (401) 762-3800
USA (401) 767-4493
Sumida
CD43150
USA (708) 956-0666
Japan (03) 3607-5111
USA (708) 956-0702
Japan (03) 3607-5428
TDK
NLC453232T-150K
USA (708) 803-6100
Japan (03) 3278-5111
USA (708) 803-6296
Japan (03) 3278-5358
_______________________________________________________________________________________
5
MAX212
Switch-Mode Power Supply
D1
1N6050
MAX212
+3V-Powered, Low-Power,
True RS-232 Transceiver
Operating Modes
–—
S D and EN determine the operation of the MAX212
as follows:
V+
–—
SD
EN
RECEIVER
OUTPUTS
L
L
High-Z
High-Z
Off
Minimum
L
H
Enabled
High-Z
Off
Minimum
H
L
High-Z
Enabled
On
Normal
H
H
Enabled
Enabled
On
LN
LP
V-
+3.3V
DRIVER
DC-DC
SUPPLY
OUTPUTS CONVERTER CURRENT
DC-DC CONVERTER
200k
MAX212
SD
TX
T_IN
+5V
LOGIC
SIGNALS
Normal
X3
T_OUT
RX
R_OUT
R_IN
X5
Shutdown
V+ and V- are disabled and the–—
transmitters are put into
a high-impedance state when SD is 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 VCC current 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,
–—
SD, 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 200kΩ series resistor between
SD and the +5V logic signal is required –—
(see Figure 2).
This protects the MAX212 by preventing SD from 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 SDis high (not shut down).
EN
GND
Figure 2. Connecting to +5V Logic
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
6
PART
POWER-SUPPLY
VOLTAGE
(V)
No. OF
TRANSMITTERS/
RECEIVERS
No. OF
RECEIVERS
ACTIVE IN
SHUTDOWN
DATA RATE
(kbps)
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
FEATURES
_______________________________________________________________________________________
+3V-Powered, Low-Power,
True RS-232 Transceiver
212 GR1
TRANSMITTER OUTPUT VOLTAGE (V)
6
T1OUT AND T2OUT
4
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
T1IN AND T2IN = GND,
T3IN = VCC = 3.0V,
T3OUT, T2OUT, T1OUT
ALL LOADED
SIMULTANEOUSLY
2
0
-2
-4
T3OUT
-6
1
2
3
4
5
6
LOAD CURRENT PER TRANSMITTER (mA)
Figure 3. Mouse Emulation Circuit Current
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.
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.
Figure 4. MAX212 Evaluation Kit
_______________________________________________________________________________________
7
MAX212
TRANSMITTER OUTPUT VOLTAGE vs.
LOAD CURRENT PER TRANSMITTER
MAX212
+3V-Powered, Low-Power,
True RS-232 Transceiver
_________________Pin Configuration
___________________Chip Topography
V CC
LP LN GND GND
V+
TOP VIEW
LN
1
24 GND
LP
2
23 V+
VCC
3
22 R1IN
SD
4
EN
5
R1OUT
6
19 R4IN
R2OUT 7
18 R5IN
R3OUT 8
17 T1OUT
R1 OUT
R4OUT
9
16 T2OUT
R5OUT 10
15 T3OUT
R2 OUT
R3 OUT
R1 IN
V CC
R2 IN
SD
EN
R3 IN
R4 IN
R5 IN
21 R2IN
MAX212
20 R3IN
T1IN 11
14 V-
T2IN 12
13 T3IN
0.15"
(3.81mm)
T1 OUT
T2 OUT
R4 OUT
R5 OUT
T3 OUT
SSOP/WIDE SO
T1 IN T3 IN
T2 IN
V-
0.1"
(2.54mm)
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 (408) 737-7600
© 1993 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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