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PDF MAX218 Data sheet ( Hoja de datos )
| Número de pieza | MAX218 | |
| Descripción | 1.8V to 4.25V-Powered / True RS-232 Dual Transceiver | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX218 (archivo pdf) en la parte inferior de esta página. Total 8 Páginas | ||
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19-0246; Rev 1; 7/95
1.8V to 4.25V-Powered,
True RS-232 Dual Transceiver
_______________General Description
The 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.
________________________Applications
Battery-Powered Equipment
Computers
Printers
Peripherals
Instruments
Modems
__________Typical Operating Circuit
____________________________Features
BETTER THAN BIPOLAR!
o Operates Directly from Two Alkaline, NiCd,
or NiMH Cells
o +1.8V to +4.25V Supply Voltage Range
o 120kbps Data Rate
o Low-Cost Surface-Mount Components
o Meets EIA/TIA-232E Specifications
o 1µA Low-Power Shutdown Mode
o Both Receivers Active During Low-Power Shutdown
o Three-State Receiver Outputs
o Flow-Through Pinout
o On-Board DC-DC Converters
o 20-Pin SSOP, Wide SO, or DIP Packages
______________Ordering Information
PART
MAX218CPP
MAX218CWP
MAX218CAP
MAX218C/D
MAX218EPP
MAX218EWP
MAX218EAP
TEMP. RANGE
0°C to +70°C
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
-40°C to +85°C
PIN-PACKAGE
20 Plastic DIP
20 Wide SO
20 SSOP
Dice*
20 Plastic DIP
20 Wide SO
20 SSOP
*Contact factory for dice specifications.
__________________Pin Configuration
1.8V
TO
4.25V
ON/OFF
ENABLE
6 VCC
1
LX
19
V+
MAX218
3
SHDN
V- 15
C1+ 18
C1- 16
7 T1IN
T1
T1OUT 14
8 T2IN
9 R1OUT
T2
R1
T2OUT 13
R1IN 12
10 R2OUT
EN
4
R2 R2IN 11
GND
5, 17, 20
TOP VIEW
LX 1
N.C. 2
SHDN 3
EN 4
GND 5
VCC 6
T1IN 7
T2IN 8
R1OUT 9
R2OUT 10
MAX218
20 GND
19 V+
18 C1+
17 GND
16 C1-
15 V-
14 T1OUT
13 T2OUT
12 R1IN
11 R2IN
DIP/SO/SSOP
________________________________________________________________ Maxim Integrated Products 1
Call toll free 1-800-998-8800 for free samples or literature.
1 page  
1.8V to 4.25V-Powered,
True RS-232 Dual Transceiver
1.8V
TO
4.25V
ON/OFF
15µH
D1
1N6050
6
VCC
1µF
C4
3
SHDN
1 19
LX V+
MAX218
V- 15
C1+ 18
16
C1-
1µF
C2
1µF
C3
0.47µF
C1
7 T1IN
T1
T1OUT 14
8 T2IN
9 R1OUT
T2
R1
T2OUT 13
R1IN 12
ENABLE
10 R2OUT
EN
4
R2 R2IN 11
GND
5, 17, 20
Figure 1. Single-Supply Operation
_______________Detailed Description
The 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 Supply
The 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 Selection
Use a 15µH inductor with a saturation current rating of at
least 350mA and less than 1Ω resistance. Table 1 lists
suppliers of inductors that meet the 15µH/350mA/1Ω
specifications.
Diode Selection
Key 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 VCC voltages. 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 Selection
Use 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 VCC to GND with at least 1µF (C4) placed
close to pins 5 and 6. If the VCC line 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.
_______________________________________________________________________________________ 5
5 Page | ||
| Páginas | Total 8 Páginas | |
| PDF Descargar | [ Datasheet MAX218.PDF ] | |
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