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參數(shù)資料
| 型號： | MAX221EAE |
| 廠商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分類： | 通用總線功能 |
| 英文描述： | Quadruple Bus Buffer Gates With 3-State Outputs 14-VQFN -40 to 85 |
| 中文描述： | LINE TRANSCEIVER, PDSO16 |
| 封裝： | SSOP-16 |
| 文件頁數(shù)： | 5/8頁 |
| 文件大?。?/td> | 110K |
| 代理商： | MAX221EAE |
M
+5V, 1μA, Single RS-232 Transceiver
with AutoShutdown
_______________________________________________________________________________________
5
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX221’s internal power supply consists of a dual
charge pump that provides a positive output voltage
(doubling charge pump) and a negative voltage (invert-
ing charge pump) from a single +5V supply. The
charge pumps operate in continuous mode. Each
charge pump requires a flying capacitor (C1, C2) and a
reservoir capacitor (C3, C4) to generate the V+ and V-
supplies.
RS-232 Transmitter
The transmitter is an inverting level translator that con-
verts CMOS-logic levels to 5.0V EIA/TIA-232 levels. It
guarantees a 250kbps data rate with worst-case loads
of 3k
in parallel with 1000pF.
When
FORCEOFF
is driven to ground, or when the
AutoShutdown circuitry senses invalid voltage levels on
the receiver input, the transmitter is disabled and the out-
put is forced into a high-impedance state. The transmitter
input does not have a pull-up resistor.
RS-232 Receiver
The MAX221’s receiver converts RS-232 signals to
CMOS-logic output levels. The receiver has an inverting
three-state output and can be active or inactive. In shut-
down (
FORCEOFF
= low) or in AutoShutdown, the
receiver is active (Table 1). Drive
EN
high to place the
receiver in a high-impedance state. The receiver is high
impedance when the MAX221 is in shutdown (
FORCE-
OFF
= low).
The MAX221’s
INVALID
output is pulled low when no
valid RS-232 signal level is detected on the receiver
input.
INVALID
is functional in any mode (Figures 2
and 3).
AutoShutdown
The MAX221 achieves 1μA supply current with Maxim’s
AutoShutdown feature, which operates when FORCEON
is low and
FORCEOFF
is high. When the device senses
no valid signal levels on the receiver input for 30μs, the
on-board charge pump and driver are shut off, reducing
supply current to 1μA. This occurs if the RS-232 cable is
disconnected or the connected peripheral transmitter is
turned off. The MAX221 turns on again when a valid
level is applied to the RS-232 receiver input. As a result,
the system saves power without changes to the existing
BIOS or operating system.
Table 1 and Figure 2c summarize the MAX221 operat-
ing modes. FORCEON and
FORCEOFF
override
AutoShutdown. When neither control is asserted, the
device selects between these states automatically,
based on the receiver input level. Figures 2a, 2b, and
3a depict valid and invalid RS-232 receiver levels.
Figure 3 shows the input levels and timing diagram for
AutoShutdown operation.
A device or another system with AutoShutdown con-
nected to the MAX221 may need time to wake up.
Figure 4 shows a circuit that forces the transmitter on
for 100ms, allowing enough time for the other system to
realize that the MAX221 is awake. If the other system
transmits valid RS-232 signals within that time, the RS-
232 ports on both systems remain enabled.
When shut down, the device’s charge pumps are off,
V+ is pulled to V
CC
, V- is pulled to ground, and the
transmitter output is high impedance. The time required
to exit shutdown is typically 100μs (Figure 3b).
Software-Controlled Shutdown
For direct software control, use
INVALID
to indicate a
DTR or Ring Indicator signal. Connect
FORCEOFF
and
FORCEON together to disable AutoShutdown so the
line acts like a
SHDN
input.
MAX221
FORCEON
EN
12
1
ROUT
9
FORCEOFF
16
10
GND
14
TIN
11
C2-
6
C2+
5
C1-
4
C1+
2
I
SHDN
RIN 8
TOUT
13
V-
7
V+
3
V
CC
C4
0.1
μ
F
0.1
μ
F
C1
0.1
μ
F
C2
0.1
μ
F
C
BYPASS
+5V
TO POWER-
MANAGEMENT
UNIT
5k
3k
INVALID
C3
0.1
μ
F
15
Figure 1. Shutdown Current Test Circuit
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX221EAE+ | 功能描述:RS-232接口集成電路 5V 1uA Single RS-232 Txr w/AutoShut RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
| MAX221EAE+T | 功能描述:RS-232接口集成電路 5V 1uA Single RS-232 Txr w/AutoShut RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
| MAX221EAE-T | 功能描述:RS-232接口集成電路 RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
| MAX221ECAE | 功能描述:RS-232接口集成電路 RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
| MAX221ECAE+ | 功能描述:RS-232接口集成電路 15kV ESD-Protected 5V 1uA RS-232 Trx RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
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