MAX3218CAP ,1A Supply Current / 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdownApplicationsBattery-Powered EquipmentSubnotebook ComputersTOP VIEWLXGND1 20PDAsINVALIDV+2 19Hand-He ..
MAX3218CAP ,1A Supply Current / 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdownELECTRICAL CHARACTERISTICS(Circuit of Figure 1, V = 1.8V to 4.25V, C1 = 0.47µF, C2 = C3 = C4 = 1µF, ..
MAX3218CAP+ ,1µA, 1.8V to 4.25V RS-232 Transceiver with AutoShutdown™ApplicationsBattery-Powered EquipmentSubnotebook ComputersTOP VIEWLXGND1 20PDAsINVALIDV+2 19Hand-He ..
MAX3218CAP+ ,1µA, 1.8V to 4.25V RS-232 Transceiver with AutoShutdown™FeaturesThe MAX3218 RS-232 transceiver is intended for bat - BETTER THAN BIPOLAR!tery-powered EIA/T ..
MAX3218EAP ,1A Supply Current / 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdownGeneral Description ________
MAX3218EAP ,1A Supply Current / 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdownFeaturesThe MAX3218 RS-232 transceiver is intended for bat- BETTER THAN BIPOLAR!tery-powered EIA/TI ..
MAX6445UK23L-T ,2.313 V, mP reset circuit with long manual reset setup periodFeaturesThe MAX6443–MAX6452 low-current microprocessor Single- or Dual-Supply Voltage Monitorsrese ..
MAX6454UT29S ,uP Supervisors with Separate VCC Reset and Manual Reset OutputsFeaturesThe MAX6453–MAX6456 are low-power, dual-voltage Precision Factory-Set Reset Thresholds Fro ..
MAX6454UT46S-T ,4.625 V, mP supervisor with separate Vcc reset and manual reset outputFeaturesThe MAX6453–MAX6456 are low-power, dual-voltage Precision Factory-Set Reset Thresholds Fro ..
MAX6455UT16S+T ,µP Supervisors with Separate VCC Reset and Manual Reset OutputsApplicationsRESET 1 6 MR RESET 1 6 MR● Set-Top Boxes ● Consumer ElectronicsMAX6453 MAX6455● DVD Pla ..
MAX6456UT29S+T ,µP Supervisors with Separate VCC Reset and Manual Reset OutputsFeaturesThe MAX6453–MAX6456 are low-power, dual-voltage ● Precision Factory-Set Reset Thresholds Fr ..
MAX6457UKD0B+T ,High-Voltage, Low-Current Voltage Monitors in SOT Packagesapplications. Each device is available in a smallPin Configurations appear at end of data sheet.SOT ..
MAX3218CAP-MAX3218EAP-MAX3218EPP
1A Supply Current / 1.8V to 4.25V-Powered RS-232 Transceiver with AutoShutdown
_______________General DescriptionThe MAX3218 RS-232 transceiver is intended for bat-
tery-powered EIA/TIA-232E and V.28/V.24 communica-
tions interfaces that need two drivers and two receivers
with minimum power consumption from a single low-
voltage supply. It provides a wide +1.8V to +4.25V
operating voltage range while maintaining true RS-232
and EIA/TIA-562 voltage levels. The MAX3218 runs
from two alkaline, NiCd, or NiMH cells without any form
of voltage regulator. A guaranteed 120kbps data rate
provides compatibility with popular software for com-
municating with personal computers.
Supply current is reduced to 1µA with Maxim’s new
AutoShutdown™ feature. When the MAX3218 does not
sense a valid signal level on the receiver inputs, the on-
board power-supply and drivers shut down. This
occurs if the RS-232 cable is disconnected or if the
transmitters of the connected peripheral are turned off.
The system turns on again when a valid level is applied
to either RS-232 receiver input. As a result, the system
saves power without changes to the existing software.
Additionally, the MAX3218 can be forced into or out of
shutdown, under logic control.
While shut down, all receivers can remain active or can
be disabled under logic control, permitting a system
incorporating the CMOS MAX3218 to monitor external
devices while in low-power shutdown. Three-state dri-
vers are provided on both receiver outputs so that multi-
ple receivers, generally of different interface standards,
can be on the same bus. The MAX3218 is available in
20-pin DIP and SSOP packages.
________________________ApplicationsBattery-Powered Equipment
Subnotebook Computers
PDAs
Hand-Held Equipment
Peripherals
Cellular Phones
____________________________Features
BETTER THAN BIPOLAR!1µA Supply Current Using AutoShutdown™Operates Directly from Two Alkaline,
NiCd or NiMH Cells+1.8V to +4.25V Single-Supply Voltage Range120kbps Data Rate GuaranteedLow-Cost Surface-Mount ComponentsMeets EIA/TIA-232E SpecificationsThree-State Receiver OutputsFlow-Through PinoutOn-Board DC-DC Converters20-Pin SSOP and DIP Packages
______________Ordering InformationContact factory for dice specifications.
MAX3218*
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™19-0380; Rev 0; 3/95
* Patent Pending
™ AutoShutdown is a trademark of Maxim Integrated Products.
__________________Pin Configuration
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
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................................................................-0.3V to (1V + V+)
Input Voltages
T_IN, FORCEON, FORCEOFF............................-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
SSOP (derate 8.00mW/°C above +70°C)..................640mW
Operating Temperature Ranges
MAX3218C_ P...................................................0°C to +70°C
MAX3218E_ P.................................................-40°C to +85°C
Storage Temperature Range ...........................-65°C to +150°C
Lead Temperature (soldering, 10sec) ...........................+300°C
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
ELECTRICAL CHARACTERISTICS (continued)(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.)
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.)
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
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
_______________Detailed DescriptionThe MAX3218 line driver/receiver is intended for bat-
tery-powered EIA/TIA-232 and V.28/V.24 communica-
tions 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 voltage range permits direct operation from a
variety of batteries without the need for a voltage regu-
lator. For example, the MAX3218 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 MAX3218.
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.
The MAX3218 is equipped with Maxim’s new propri-
etary AutoShutdown™ circuitry. This achieves a 1µA
supply current by shutting down the device when the
RS-232 cable is disconnected or when the connected
peripheral transmitters are turned off. While shut down,
both receivers can remain active or can be disabled
under logic control. With this feature, the MAX3218 can
be in low-power shutdown mode and still monitor activi-
ty on external devices. Three-state drivers are provid-
ed on both receiver outputs.
Three-state drivers on both receiver outputs are provid-
ed so that multiple receivers, generally of different inter-
face standards, can be wire-ORed at the UART.
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.
MAX3218
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
______________________________________________________________Pin Description™ LapLink is a trademark of Traveling Software, Inc.
AutoShutdown is a trademark of Maxim Integrated Products.
MAX3218
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 deter-
mine 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 else-
where (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
values may be required.
1µA Supply Current, 1.8V to 4.25V-Powered
RS-232 Transceiver with AutoShutdown™
Table 1. Suggested Component Suppliers
