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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 1A 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--LapLinkTM 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-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 1A 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
___________Typical Operating Circuit
23 +3.3V V+ 3V CC 1 LN 2 LP 14 V-
________________________Applications
Computers Notebooks/Palmtops/Subnotebooks Printers Peripherals Instruments
DC-DC CONVERTER SHUTDOWN 4 SD
MAX212
T1 T1OUT 17
11 T1IN
_______________Ordering Information
12 T2IN T2 T2OUT 16
PART MAX212CWG MAX212CAG MAX212C/D MAX212EWG MAX212EAG
TEMP. RANGE 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C
PIN-PACKAGE 24 Wide SO 24 SSOP Dice* 24 Wide SO 24 SSOP
13 T3IN T3 T3OUT 15
6 R1OUT
R1
R1IN 22
7 R2OUT
R2
R2IN 21
* Dice are tested at TA = +25C only.
8 R3OUT R3 R3IN 20
EV KIT MAX212EVKIT-SSOP
TEMP. RANGE 0C to +70C
BOARD TYPE Surface Mount
9 R4OUT
R4
R4IN 19
10 R5OUT
R5
R5IN 18
EN ENABLE 5
GND 24
TMLapLink 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 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 = +70C) Wide SO (derate 11.76mW/C above +70C)...............941mW SSOP (derate 8.00mW/C above +70C) .....................640mW Lead Temperature (soldering, 10sec) .............................+300C
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 DC CHARACTERISTICS Operating Voltage Range VCC 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 (VHIGH, VLOW) Output Resistance EIA/TIA-232E Short-Circuit Current All transmitters loaded 3k to GND VCC = V- = V+ = 0V, -2V < T_OUT < 2V 5.0 300 28 100 5.5 V mA -15V < VIN < 15V 3 0.7 5 7 -25 0.4 2.8 +25 V V V V k - -- 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 T_IN; VCC = 3.3V IOUT = 1.0mA IOUT = -1.0mA EN = GND, 0V < R_OUT < VCC VCC - 0.5 10 VCC / 3 2VCC / 3 1 1 0.3 0.25 V V A A V V V A Meets or exceeds EIA/TIA-232E specifications No load, VCC = 3.3V - -- SD = EN = GND, R_IN = GND or VCC - -- SD = GND, EN = VCC, R_IN = GND or VCC 3.0 1.5 1 1 3.6 3.0 15 15 V mA A A CONDITIONS MIN TYP MAX UNITS
2
_______________________________________________________________________________________
+3V-Powered, Low-Power, True RS-232 Transceiver
TIMING CHARACTERISTICS
(VCC = 3.0V to 3.6V, TA = TMIN to TMAX, 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 tER tDR tET tDT tPHLR tPLHR tPHLT tPLHT 150pF load 2500pF 3k load RL = 3k to 7k, CL = 50pF to 2500pF, measured from +3V to -3V or -3V to +3V 4.0 Includes power-supply start-up SYMBOL CONDITIONS 1000pF 3k 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 s ns ns ns V/s
MAX212
__________________________________________Typical Operating Characteristics
(VCC = 3.3V, TA = +25C, 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/ 3k 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 3k 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)
(VCC = 3.3V, TA = +25C, 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/s) 11 10 9 8 FALLING EDGE ALL TRANSMITTERS LOADED SIMULTANEOUSLY w/ SPECIFIED CAPACITANCE AND 3k 500 1500 2500 3500 RISING EDGE
212 GR6
180 120kbps 160 SUPPLY POWER (mW) ALL TRANSMITTERS AT SPECIFIED DATA RATES w/ 2500pF AND 3k LOADS
80 70 SUPPLY CURRENT (mA) 60 50 64kbps 40 30 ALL TRANSMITTERS AT SPECIFIED CAPACITANCE AND DATA RATES w/ 3k 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 VCC FUNCTION Inductor/Diode Connection Point Inductor/Diode Connection Point Supply Voltage Input, 3.0V to 3.6V 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. Receiver Enable Control. Connect to VCC for normal operation. Connect to GND to force the receiver outputs into a high-Z state. Receiver Outputs, swing GND to VCC 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 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 1A 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.
4
- -- SD
5
EN
6-10 11-13 14 15-17 18-22 23 24
R1OUTR5OUT T1IN-T3IN VT3OUTT1OUT R5IN-R1IN V+ GND
4
_______________________________________________________________________________________
+3V-Powered, Low-Power, True RS-232 Transceiver
Switch-Mode Power Supply
D1 1N6050 C1 0.68F +3.3V C3 0.33F SHUTDOWN 4 SD L 15H D2 1N6050 C2 0.33F V-
MAX212
23 V+ 3V CC
1 LN
2 LP +3.3V TO 6.5V DC-DC CONVERTER
14
MAX212
T1 T1OUT 17 T2OUT 16
11 T1IN
12 T2IN
T2
13 T3IN 6 R1OUT
T3 R1
T3OUT 15 R1IN 22
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 15H inductor with a saturation current rating of at least 350mA and under 1 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 0.33F close to the MAX212. Increase this to 4.7F 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.
7 R2OUT
R2
R2IN 21
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.
8 R3OUT
R3
R3IN 20
9 R4OUT
R4
R4IN 19
10 R5OUT
R5 GND 24
R5IN 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 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.
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
+3V-Powered, Low-Power, True RS-232 Transceiver MAX212
Operating Modes - -- S D and EN determine the operation of the MAX212 as follows:
V+ LN LP V-
- -- SD
EN
RECEIVER OUTPUTS
DRIVER DC-DC SUPPLY OUTPUTS CONVERTER CURRENT
+3.3V DC-DC CONVERTER 200k SD T_IN +5V LOGIC SIGNALS
L L H H
L H L H
High-Z Enabled High-Z Enabled
High-Z High-Z Enabled Enabled
Off Off On On
Minimum Minimum Normal Normal
MAX212
TX X3 T_OUT R_IN
R_OUT
RX 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.
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.
Driving the MAX212 from 5V Logic
The MAX212 can interface with 5V logic while it operates from a 3V supply, however a 200k 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).
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 3k. For applica-
____________________________+3V Powered RS-232 Transceivers from Maxim
PART MAX212 MAX560 MAX561 MAX562 POWER-SUPPLY VOLTAGE (V) 3.0 to 3.6 3.0 to 3.6 3.0 to 3.6 2.7 to 5.25 No. OF TRANSMITTERS/ RECEIVERS 3/5 4/5 4/5 3/5 No. OF RECEIVERS ACTIVE IN SHUTDOWN 5 2 0 5 DATA RATE (kbps) 250 120 120 250 FEATURES True RS-232 from +3V 2 receivers active in shutdown Pin compatible with MAX241 Wide supply range
6
_______________________________________________________________________________________
+3V-Powered, Low-Power, True RS-232 Transceiver
TRANSMITTER OUTPUT VOLTAGE vs. LOAD CURRENT PER TRANSMITTER
TRANSMITTER OUTPUT VOLTAGE (V) T1OUT AND T2OUT T1IN AND T2IN = GND, T3IN = VCC = 3.0V, T3OUT, T2OUT, T1OUT ALL LOADED SIMULTANEOUSLY
212 GR1
6 4 2 0 -2 -4 -6 1 2 3 4 5 6 LOAD CURRENT PER TRANSMITTER (mA) T3OUT
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.
MAX212
______________________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 1A. While shut down, all receivers can remain active or can be disabled under logic control via the EN input.
Figure 3. Mouse Emulation Circuit Current
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 3k 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
+3V-Powered, Low-Power, True RS-232 Transceiver MAX212
_________________Pin Configuration
TOP VIEW
LN LP VCC SD EN R1OUT 1 2 3 4 5 6 24 GND 23 V+ 22 R1IN 21 R2IN
V CC SD EN R1 IN R2 IN R3 IN R4 IN R5 IN
___________________Chip Topography
V CC LP LN GND GND V+
MAX212
20 R3IN 19 R4IN 18 R5IN 17 T1OUT 16 T2OUT 15 T3OUT 14 V13 T3IN
R1 OUT R2 OUT R3 OUT R4 OUT R5 OUT 0.15" (3.81mm) T1 OUT T2 OUT T3 OUT
R2OUT 7 R3OUT 8 R4OUT 9
R5OUT 10 T1IN 11 T2IN 12
SSOP/WIDE SO
T1 IN T3 IN T2 IN 0.1" (2.54mm) V-
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 (c) 1993 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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