MAX3381EEUP Maxim Integrated, MAX3381EEUP Datasheet - Page 6

• Manufacturer Part Number: MAX3381EEUP
• Description: RS-232 Interface IC
• Manufacturer: Maxim Integrated
• Series: MAX3380E, MAX3381Er

Specifications of MAX3381EEUP

• Data Rate: 250 Kbps
• Operating Supply Voltage: 2.35 V to 5.5 V
• Supply Current: 1 mA
• Operating Temperature Range: 0 C to + 70 C
• Function: Transceiver
• Number Of Drivers: 2
• Number Of I/os: 8
• Number Of Receivers: 2
• Propagation Delay Time Ns: 0.15 us
• Shutdown: Yes

+2.35V to +5.5V, 1µA, 2Tx/2Rx RS-232 Transceivers
with ±15kV ESD-Protected I/O and Logic Pins
The MAX3380E/MAX3381E are RS-232 transceivers that
maximize battery life by reducing current consumption
at low battery levels. When the supply voltage is above
+3.7V, the RS-232 outputs are at ±5.5V, which is com-
pliant with the RS-232 standard. As the supply voltage
drops below the +3.1V set point, the RS-232 outputs
change to ±3.7V, which is compatible with the RS-232
standard. The outputs will remain at the compatible lev-
els until the supply voltage rises above +3.5V, where
they return to compliant levels. 400mV of hysteresis pro-
tects against power-supply bounce that may cause
numerous mode changes.
Most devices that use charge pumps to double and
invert voltages consume higher current when the supply
voltage is less than half of the required output voltage.
This is due to the fact that the charge pump is constant-
ly operating because the output voltage is below the
regulation voltage. This requires more supply current
because the output will never reach the regulation volt-
age and switch off. The MAX3380E/MAX3381E reduce
6
10, 11
14, 15
16, 17
PIN
8, 9
12
13
18
19
20
_______________________________________________________________________________________
1
2
3
4
5
6
7
FORCEOFF
FORCEON
INVALID
R_OUT
T_OUT
NAME
T_IN
R_IN
GND
C1+
C2+
V
C1-
C2-
V+
V
V-
CC
L
Positive Terminal of Voltage-Doubler Charge-Pump Capacitor
+5.5V/+4.0V Generated by the Charge Pump
Negative Terminal of Voltage-Doubler Charge-Pump Capacitor
Positive Terminal of Inverting Charge-Pump Capacitor
Negative Terminal of Inverting Charge-Pump Capacitor
-5.5V/-4.0V Generated by the Charge Pump
INVALID is asserted if any inputs of the receivers are in an invalid state;
-0.3V < V
TTL/CMOS Transmitter Inputs Referenced to V
TTL/CMOS Receiver Outputs Referenced to V
Force-On Input. Drive high to override automatic circuitry keeping transmitters on
(FORCEOFF must be high) (Table 1).
Logic Level Supply. +1.65V to +5.5V, sets CMOS logic thresholds and CMOS
outputs.
RS-232 Receiver Inputs (R2IN, R1IN)
RS-232 Transmitter Outputs (T2OUT, T1OUT)
Ground
Force-Off Input. Drive low to shut down transmitters and on-board power supply.
This overrides all automatic circuitry and FORCEON (Table 1).
+2.35V to +5.5V Supply Voltage
Detailed Description
R
_
IN
< +0.3V
FUNCTION
the output voltage requirement allowing the charge
pump to operate with supply voltages down to +2.35V.
The MAX3380E/MAX3381Es’ internal power supply is a
dual-mode regulated charge pump. The output regula-
tion point depends on V
V
V
For supply voltages above +3.7V, the charge pump will
generate +5.5V at V+ and -5.5V at V-. The charge
pumps operate in a discontinuous mode. If the output
voltages are less than ±5.5V, the charge pumps are
enabled; if the output voltages exceed ±5.5V, the
charge pumps are disabled.
For supply voltages below +2.95V, the charge pump
will generate +4.0V at V+ and -4.0V at V-. The charge
pumps operate in a discontinuous mode.
Each charge pump requires a flying capacitor (C1, C2)
and a reservoir capacitor (C3, C4) to generate the V+
and V- supplies (see Typical Operating Circuit).
L
CC
CC
L
(R2OUT, R1OUT)
(T1IN, T2IN)
< +3.7V.
moves through the switchover region of +2.95V <
Dual-Mode Regulated Charge-Pump
CC
and the direction in which
Pin Description
Voltage Converter
PROTECTED
ESD
—
—
—
—
—
—
—
✔
✔
✔
—
✔
✔
—
✔
—