MAX3228EBV-T Maxim Integrated, MAX3228EBV-T Datasheet - Page 7

• Manufacturer Part Number: MAX3228EBV-T
• Description: RS-232 Interface IC 2.5-5.5V Transceiver
• Manufacturer: Maxim Integrated
• Series: MAX3228, MAX3229r

Specifications of MAX3228EBV-T

• Data Rate: 250 Kbps
• Operating Supply Voltage: 2.5 V to 5.5 V
• Supply Current: 10 uA
• Operating Temperature Range: - 40 C to + 85 C
• Mounting Style: SMD/SMT
• Package / Case: UCSP-20 6 x 5
• Number Of Drivers: 2
• Number Of Receivers: 2

Figure 2a. MAX322_ Entering 1µA Supply Mode via
AutoShutdown
For example, a three-cell NiMh battery system starts at
V
output voltage of ±5.5V. As the battery discharges, the
MAX3228/MAX3229 maintain the outputs in regulation
until the battery voltage drops below +3.1V. Then the
output regulation points change to ±4.0V
When V
output voltage of ±4.0V, while V
and +3.5V. When V
age of +3.5V, the charge pump switches modes to
generate an output of ±5.5V.
Table 1 shows different supply schemes and their
operating voltage ranges.
The transmitters are inverting level translators that con-
vert CMOS-logic levels to RS-232 levels. The
MAX3228/MAX3229 will automatically reduce the RS-
232 compliant levels (±5.5V) to RS-232 compatible lev-
els (±4.0V) when V
The reduced levels also reduce supply current require-
ments, extending battery life. Built-in hysteresis of
approximately 400mV for V
output levels do not change if V
sudden current draw causing the supply voltage to
drop slightly. The outputs will return to RS-232 compli-
ant levels (±5.5V) when V
+3.5V.
The MAX3228/MAX3229 transmitters guarantee a
250kbps data rate with worst-case loads of 3kΩ in par-
allel with 1000pF.
When FORCEOFF is driven to ground, the transmitters
and receivers are disabled and the outputs become
high impedance. When the AutoShutdown circuitry
senses that all receiver and transmitter inputs are inac-
tive for more than 30µs, the transmitters are disabled
and the outputs go to a high-impedance state. When
CC
+0.3V
-0.3V
R_IN
*TRANSMITTERS ARE DISABLED, REDUCING SUPPLY CURRENT TO 1µA IF
ALL RECEIVER INPUTS ARE BETWEEN +0.3V AND -0.3V FOR AT LEAST 30µs.
= +3.6V, and the charge pump will generate an
CC
is rising, the charge pump will generate an
_______________________________________________________________________________________
CC
CC
falls below approximately +3.1V.
rises above the switchover volt-
CC
CC
RS-232 Transmitters
+2.5V to +5.5V RS-232 Transceivers
rises above approximately
ensures that the RS-232
CC
CC
COUNTER
30µs
R
is between +2.5V
is noisy or has a
AND TRANSMITTERS
POWER SUPPLY
INVALID
TO MAX322 _
the power is off, the MAX3228/MAX3229 permit the
transmitter outputs to be driven up to ±12V.
The transmitter inputs do not have pullup resistors.
Connect unused inputs to GND or V
The MAX3228/MAX3229 receivers convert RS-232 sig-
nals to logic output levels. All receivers have inverting
three-state outputs and can be active or inactive. In
shutdown (FORCEOFF = low) or in AutoShutdown, the
MAX3228/MAX3229 receivers are in a high-impedance
state (Table 3).
The MAX3228/MAX3229 feature an INVALID output that
is enabled low when no valid RS-232 signal levels have
been detected on any receiver inputs. INVALID is func-
tional in any mode (Figures 2 and 3).
Figure 2b. MAX322_ with Transmitters Enabled Using
AutoShutdown
Figure 2c. MAX322_ AutoShutdown Logic
+2.7V
-2.7V
R_IN
*TRANSMITTERS ARE ENABLED IF:
ANY RECEIVER INPUT IS GREATER THAN +2.7V OR LESS THAN -2.7V.
ANY RECEIVER INPUT HAS BEEN BETWEEN +0.3V AND -0.3V FOR LESS THAN 30µs.
V
INVALID IS AN INTERNALLY GENERATED SIGNAL
THAT IS USED BY THE AUTOSHUTDOWN LOGIC
AND APPEARS AS AN OUTPUT OF THE DEVICE.
POWER DOWN IS ONLY AN INTERNAL SIGNAL.
IT CONTROLS THE OPERATIONAL STATUS OF
THE TRANSMITTERS AND THE POWER SUPPLIES.
CC
V
L
FORCEON
INVALID
FORCEOFF
V
L
RS-232 Receivers
COUNTER
L
in UCSP
30µs
R
.
POWER DOWN
POWER SUPPLY
INVALID
TO MAX322 _
7