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参数资料
| 型号： | MAX218 |
| 厂商： | Maxim Integrated Products, Inc. |
| 英文描述： | 16-Bit Buffers/Drivers With 3-State Outputs 48-SSOP -40 to 85 |
| 中文描述： | 1.8V至4.25V供电、双路、真RS-232收发器 |
| 文件页数： | 5/8页 |
| 文件大小： | 92K |
| 代理商： | MAX218 |
M
1.8V to 4.25V-Powered,
True RS -232 Dual Transc eiver
_______________________________________________________________________________________
5
_______________Detailed Desc ription
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.
S witc h-Mode Power S upply
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 1
resistance. Table 1 lists
suppliers of inductors that meet the 15μH/350mA/1
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 V
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 V
CC
to GND with at least 1μF (C4) placed
close to pins 5 and 6. If the V
CC
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.
R1
R2
T1
T2
T1OUT
T2OUT
T1IN
T2IN
R1OUT
R2OUT
R1IN
R2IN
GND
EN
V
CC
SHDN
LX
C1+
C1-
V-
6
3
7
8
9
10
11
12
13
14
16
18
15
4
5, 17, 20
MAX218
ENABLE
ON/OFF
1.8V
TO
4.25V
1
V+
19
1
μ
F
C4
1
μ
F
C2
1
μ
F
C3
0.47
μ
F
C1
15
μ
H
D1
1N6050
Figure 1. Single-Supply Operation
相关PDF资料 |
PDF描述 |
|---|---|
| MAX218CAP | 16-Bit Buffers/Drivers With 3-State Outputs 48-SSOP -40 to 85 |
| MAX218CPP | Replaced by SN74ABT16245A : 16-Bit Bus Transceivers With 3-State Outputs 48-TSSOP -40 to 85 |
| MAX218CWP | Replaced by SN74ABT16245A : 16-Bit Bus Transceivers With 3-State Outputs 48-SSOP -40 to 85 |
| MAX218EAP | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| MAX218EPP | 16-Bit Bus Transceivers With 3-State Outputs 48-TSSOP -40 to 85 |
相关代理商/技术参数 |
参数描述 |
|---|---|
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