MAX218EAP ,1.8V to 4.25V-Powered, True RS-232 Dual TransceiverMAX21819-0246; Rev 1; 7/951.8V to 4.25V-Powered,True RS-232 Dual Transceiver_______________
MAX218EAP+ ,1.8V to 4.25V Powered, True RS-232 Dual TransceiverApplicationsMAX218CWP 0°C to +70°C 20 Wide SOBattery-Powered EquipmentMAX218CAP 0°C to +70°C 20 SSO ..
MAX218EWP ,1.8V to 4.25V-Powered, True RS-232 Dual TransceiverGeneral Description ________
MAX2205EBS ,RF Power Detectors in UCSPELECTRICAL CHARACTERISTICS (MAX2205–MAX2208)(V = +2.7V to +5.0V, SHDN = +2.0V, no RF signal applied ..
MAX2205EBS+T ,RF Power Detectors in UCSPfeatures 40dB dynamic range, making Ordering Informationit ideally suited to GSM/EDGE
MAX2205EBS+T10 ,RF Power Detectors in UCSPapplications. TheMAX2207 offers reduced current consumption for TDMAPART TEMP RANGE BUMP-PACKAGE
MAX528EPP+ ,Octal, Serial, 8-Bit DAC with Output BuffersGeneral Description
The MAX528/MAX529 are monolithic devices combining
an octal 8-bit, digital- ..
MAX528EWG ,Octal, 8-Bit, Serial DACs with Output Buffer19-4193; Rev 2; 5/94
MAX528EWG+ ,Octal, Serial, 8-Bit DAC with Output BuffersApplications
Digital Gain and Offset Adjustment
Digital Calibration
Multiple Trim Pot Replac ..
MAX5290AETE ,Buffered, Fast-Settling, Dual, 12-/10-/8-Bit, Voltage-Output DACsFeaturesThe MAX5290–MAX5295 dual, 12-/10-/8-bit, voltage- Dual, 12-/10-/8-Bit Serial DACs in 4mm x ..
MAX5290AEUD ,Buffered, Fast-Settling, Dual, 12-/10-/8-Bit, Voltage-Output DACsMAX5290–MAX529519-3005; Rev 0; 11/03Buffered, Fast-Settling, Dual, 12-/10-/8-Bit,Voltage-Output DACs
MAX5290BEUD ,Buffered, Fast-Settling, Dual, 12-/10-/8-Bit, Voltage-Output DACsapplications. Multiple devices1/2 LSB (max) MAX5294/MAX5295 (8-Bit)can share a common serial interf ..
MAX218CAP-MAX218CWP-MAX218EAP-MAX218EWP
1.8V to 4.25V-Powered, True RS-232 Dual Transceiver
_______________General DescriptionThe MAX218 RS-232 transceiver is intended for battery-
powered EIA/TIA-232E and V.28/V.24 communications
interfaces that need two drivers and two receivers with
minimum power consumption. It provides a wide +1.8V
to +4.25V operating voltage range while maintaining
true RS-232 and EIA/TIA-562 voltage levels. The
MAX218 runs from two alkaline, NiCd, or NiMH cells
without any form of voltage regulator.
A shutdown mode reduces current consumption to
1µA, extending battery life in portable systems. While
shut down, all receivers can remain active or can be
disabled under logic control, permitting a system incor-
porating the CMOS MAX218 to monitor external
devices while in low-power shutdown mode.
A guaranteed 120kbps data rate provides compatibility
with popular software for communicating with personal
computers. Three-state drivers are provided on all
receiver outputs so that multiple receivers, generally of
different interface standards, can be wire-ORed at the
UART. The MAX218 is available in 20-pin DIP, SO, and
SSOP packages.
________________________ApplicationsBattery-Powered Equipment
Computers
Printers
Peripherals
Instruments
Modems
____________________________Features
BETTER THAN BIPOLAR!Operates Directly from Two Alkaline, NiCd,
or NiMH Cells+1.8V to +4.25V Supply Voltage Range120kbps Data RateLow-Cost Surface-Mount ComponentsMeets EIA/TIA-232E Specifications1µA Low-Power Shutdown ModeBoth Receivers Active During Low-Power ShutdownThree-State Receiver OutputsFlow-Through PinoutOn-Board DC-DC Converters20-Pin SSOP, Wide SO, or DIP Packages
______________Ordering Information*Contact factory for dice specifications.
MAX218
1.8V to 4.25V-Powered,rue RS-232 Dual Transceiver
________________________________________________________________Maxim Integrated Products1
__________________Pin Configuration
__________Typical Operating Circuit
Call toll free 1-800-998-8800 for free samples or literature.19-0246; Rev 1; 7/95
MAX218
1.8V to 4.25V-Powered,rue RS-232 Dual Transceiver_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VCC= 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA= TMINto TMAX, unless otherwise noted.
Typical values are at VCC= 3.0V, TA= +25°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.
Supply Voltages
VCC....................................................................-0.3V to +4.6V
V+..........................................................(VCC- 0.3V) to +7.5V
V-.......................................................................+0.3V to -7.4V
VCCto V-..........................................................................+12V
LX................................................................-0.3V to (1V + V+)
Input Voltages
T_IN, EN, S—H—D—N–.................................................-0.3V to +7V
R_IN.................................................................................±25V
Output Voltages
T_OUT.............................................................................±15V)
R_OUT....................................................-0.3V to (VCC+ 0.3V)
Short-Circuit Duration, R_OUT, T_OUT to GND .......Continuous
Continuous Power Dissipation (TA= +70°C)
Plastic DIP (derate 11.11mW/°C above +70°C)..........889mW
Wide SO (derate 10.00mW/°C above +70°C)..............800mW
SSOP (derate 8.00mW/°C above +70°C)...................640mW
Operating Temperature Ranges
MAX218C_ P.....................................................0°C to +70°C
MAX218E_ P...................................................-40°C to +85°C
Storage Temperature Range ...........................-65°C to +150°C
Lead Temperature (soldering, 10sec) ...........................+300°C
Note 1:Entire supply current for the circuit of Figure 1.
MAX218
1.8V to 4.25V-Powered,rue RS-232 Dual Transceiver
_______________________________________________________________________________________3
TIMING CHARACTERISTICS(Circuit of Figure 1, VCC= 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, L1 = 15µH, TA= TMINto TMAX, unless otherwise noted.
Typical values are at VCC= 3.0V, TA= +25°C.)
______________________________________________________________Pin Description
MAX218
1.8V to 4.25V-Powered,rue RS-232 Dual Transceiver_______________________________________________________________________________________
TRANSMITTER OUTPUT VOLTAGE vs.
LOAD CAPACITANCE AT 120kbpsMAX3218-04
LOAD CAPACITANCE (pF)
TRANSMITTER OUTPUT VOLTAGE (V)
SLEW RATE vs.
TRANSMITTER CAPACITANCE
MAX3218-05
LOAD CAPACITANCE (pF)
SLEW RATE (V/
__________________________________________Typical Operating Characteristics
(Circuit of Figure 1, VCC= 1.8V, all transmitter outputs loaded with 3kΩ, TA = +25°C, unless otherwise noted.)
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX3218-01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
TRANSMITTING SUPPLY CURRENT
vs. LOAD CAPACITANCE
MAX3218-02
LOAD CAPACITANCE (pF)
SUPPLY CURRENT (mA)
4000
MAX218
1.8V to 4.25V-Powered,rue RS-232 Dual Transceiver
_______________________________________________________________________________________5
_______________Detailed DescriptionThe MAX218 line driver/receiver is intended for battery-
powered EIA/TIA-232 and V.28/V.24 communications
interfaces that require two drivers and two receivers.
The operating voltage extends from 1.8V to 4.25V, yet
the device maintains true RS-232 and EIA/TIA-562
transmitter output voltage levels. This wide supply volt-
age range permits direct operation from a variety of
batteries without the need for a voltage regulator. For
example, the MAX218 can be run directly from a single
lithium cell or a pair of alkaline cells. It can also be run
directly from two NiCd or NiMH cells from full-charge
voltage down to the normal 0.9V/cell end-of-life point.
The 4.25V maximum supply voltage allows the two
rechargeable cells to be trickle- or fast-charged while
driving the MAX218.
The circuit comprises three sections: power supply,
transmitters, and receivers. The power-supply section
converts the supplied input voltage to 6.5V, providing 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 120kbps data rates, providing compatibility with
LapLink™ and other high-speed communications soft-
ware. A shutdown mode extends battery life by reduc-
ing supply current to 0.04µA. While shut down, all
receivers can either remain active or be disabled under
logic control. With this feature, the MAX218 can be in
low-power shutdown mode and still monitor activity on
external devices. Three-state drivers are provided on
both receiver outputs.
Switch-Mode Power SupplyThe switch-mode power supply uses a single inductor
with one diode and three small capacitors to generate
±6.5V from an input voltage in the 1.8V to 4.25V
range.
Inductor SelectionUse a 15µH inductor with a saturation current rating of at
least 350mA and less than 1Ωresistance. Table 1 lists
suppliers of inductors that meet the 15µH/350mA/1Ω
specifications.
Diode SelectionKey diode specifications are fast recovery time (<10ns),
average current rating (>100mA), and peak current rat-
ing (>350mA). Inexpensive fast silicon diodes, such as
the 1N6050, are generally recommended. More expen-
sive Schottky diodes improve efficiency and give slightly
better performance at very low VCCvoltages. Table 1
lists suppliers of both surface-mount and through-hole
diodes. 1N914s are usually satisfactory, but specifica-
tions and performance vary widely with different manu-
facturers.
Capacitor SelectionUse capacitors with values at least as indicated in
Figure 1. Capacitor C2 determines the ripple on V+,
but not the absolute voltage. Capacitors C1 and C3
determine both the ripple and the absolute voltage of
V-. Bypass VCCto GND with at least 1µF (C4) placed
close to pins 5 and 6. If the VCCline is not bypassed
elsewhere (e.g., at the power supply), increase C4 to
4.7µF.
You may use ceramic or polarized capacitors in all
locations. If you use polarized capacitors, tantalum
types are preferred because of the high operating fre-
quency of the power supplies (about 250kHz). If alu-
minum electrolytics are used, higher capacitance val-
ues may be required.
™ LapLink is a trademark of Traveling Software, Inc.
MAX218
1.8V to 4.25V-Powered,rue RS-232 Dual Transceiver_______________________________________________________________________________________
RS-232 DriversThe two drivers are identical, and deliver EIA/TIA-232E
and EIA/TIA-562 output voltage levels when VDDis
between 1.8V and 4.25V. The transmitters drive up to
3kΩin parallel with 1000pF at up to 120kbps. Connect
unused driver inputs to either GND or VCC. Disable the
drivers by takingS—H—D—N–low. The transmitter outputs are
forced into a high-impedance state whenS—H—D—N–is low.
RS-232 ReceiversThe two receivers are identical, and accept both
EIA/TIA-232E and EIA/TIA-562 input signals. The
CMOS receiver outputs swing rail-to-rail. When EN is
high, the receivers are active regardless of the state of—H—D—N–. When EN is low, the receiver outputs are put
into a high-impedance state. This allows two RS-232
ports (or two ports of different types) to be wired-ORed
at the UART.
Operating Modes—H—D—N–and EN determine the MAX218’s mode of opera-
tion, as shown in Table 2.
Table 2. Operating Modes
ShutdownWhenS—H—D—N–is low, the power supplies are disabled and
the transmitters are put into a high-impedance state.
Receiver operation is not affected by takingS—H—D—N–low.
Power consumption is dramatically reduced in shutdown
mode. Supply current is minimized when the receiver
inputs are static in any of three states: floating (ground),
GND, or VCC.
__________Applications Information
Operation from Regulated/Unregulated
Dual System Power SuppliesThe MAX218 is intended for use with three different
power-supply sources: it can be powered directly from
a battery, from a 3.0V or 3.3V power supply, or simulta-
neously from both. Figure 1 shows the single-supply
configuration. Figure 2 shows the circuit for operation
from both a 3V supply and a raw battery supply—an
ideal configuration where a regulated 3V supply is
being derived from two cells. In this application, the
MAX218’s logic levels remain appropriate for interface
with 3V logic, yet most of the power for the MAX218 is
drawn directly from the battery, without suffering the
efficiency losses of the DC-DC converter. This pro-
longs battery life.
Bypass the input supplies with 0.1µF at VCC(C4) and at
least 1µF at the inductor (C5). Increase C5 to 4.7µF if
the power supply has no other bypass capacitor con-
nected to it.
Table 1. Suggested Component Suppliers
