ADM3232ERNZ datasheet(8/16 Pages) UMW

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DESCRIPTION

The ADM3222A/3232E transceivers meet the EIA/

TIA-232 and V.28/V.24 communication proto-

cols and can be implemented in battery-pow-

ered, portable, or hand-held applications such as

notebook or palmtop computers. The ADM3222A/

3232E

devices all feature

ADM3222A

proprietary on-board

charge pump circuitry that generates 2

x V

CC for RS-232 voltage levels from a single

+3.0V to +5.5V power supply. This series is

ideal for +3.3V-only systems, mixed +3.3V to

+5.5V systems, or +5.0V-only systems that re-

quire true RS-232 performance. The ADM3222A/

3232E

series have drivers that operate at a typi-

cal data rate of 235Kbps fully loaded.

The

and ADM3232E are 2-driver/2-re-

ceiver devices ideal for portable or hand-held

applications.The ADM3222A features a 1

µA

shutdown mode that reduces power consump-

tion and extends battery life in portable systems.

Its receivers remain active in shutdown mode,

allowing external devices such as modems to be

monitored using only 1

µA supply current.

THEORY OF OPERATION

The ADM3222A/3232E series are made up of three

basic circuit blocks: 1. Drivers, 2. Receivers,

and 3. the Sipex proprietary charge pump.

Drivers

The drivers are inverting level transmitters that

convert TTL or CMOS logic levels to

±5.0V

EIA/TIA-232 levels inverted relative to the in-

put logic levels. Typically, the RS-232 output

voltage swing is

±5.5V with no load and at least

±5V minimum fully loaded. The driver outputs

are protected against infinite short-circuits to

ground without degradation in reliability. Driver

outputs will meet EIA/TIA-562 levels of

±3.7V

with supply voltages as low as 2.7V.

The drivers typically can operate at a data rate

of 235Kbps. The drivers can guarantee a data

rate of 120Kbps fully loaded with 3K

Ω in

parallel with 1000pF, ensuring compatibility

with PC-to-PC communication software.

The slew rate of the driver output is internally

limited to a maximum of 30V/

µs in order to meet

the EIA standards (EIA RS-232D 2.1.7, Para-

graph 5). The transition of the loaded output

from HIGH to LOW also meets the monotonic-

ity requirements of the standard.

The ADM3222A/3232E drivers can maintain high

data rates up to 235Kbps fully loaded. Figure 8

shows a loopback test circuit used to test the

RS-232 drivers. Figure 9 shows the test results

of the loopback circuit with all drivers active at

120Kbps with RS-232 loads in parallel with

1000pF capacitors. Figure 10 shows the test

results where one driver was active at 235Kbps

and all drivers loaded with an RS-232 receiver

in parallel with a 1000pF capacitor. A solid

RS-232 data transmission rate of 120Kbps

provides compatibility with many designs

in personal computer peripherals and LAN

applications.

The ADM3222A driver's output stages are tur-

ned off (tri-state) when the device is in shut-

down mode. When the power is off, the

ADM3222A device permits the outputs to be

driven up to

±12V. The driver's inputs do not

have pull-up resistors.Designers should con-

nect unused inputs to V

CC or GND.

In the shutdown mode, the supply current falls to

less than 1

µA, where SHDN = LOW. When the

ADM3222A

device is shut down, the device's

driver outputs are disabled (tri-stated) and the

charge pumps are turned off with V+ pulled

down to V

CC and V- pulled to GND.

The time

required to exit shutdown is typically 100

µs.

Connect SHDN to V

CC if the shutdown mode is

not used. SHDN has no effect on RxOUT or

RxOUTB. As they become active, the two driver

outputs go to opposite RS-232 levels where one

driver input is HIGH and the other LOW. Note

that the drivers are enabled only when the

magnitude of V- exceeds approximately 3V.

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友台半导体有限公司

True +3.0V to +5.5V RS-232 Transceivers

UMW

ADM3222A/3232E

ADM3232ERNZ Datasheet(PDF) 8 Page - Guangdong Youtai Semiconductor Co., Ltd.

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