MAX3385EEAP Maxim Integrated Products, MAX3385EEAP Datasheet - Page 5

• Manufacturer Part Number: MAX3385EEAP
• Description: Dual Transmitter/Receiver RS-232 20-Pin SSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX3385EEAP

• Package: 20SSOP
• Data Transmission Topology: Point-to-Point
• Interface Standards: EIA/TIA-232|RS-232|V.24|V.28
• Data Rate: 0.25(Min) Mbps
• Function: Line Transmitter/Receiver
• Number Of Transceivers: 1
• Number Of Transmitters: 2
• Transmitter Signal Type: Single-Ended
• Transmitter Communication Type: RS-232
• Typical Single Supply Voltage: 3.3|5 V

The MAX3385E’s internal power supply consists of a
regulated dual charge pump that provides output volt-
ages of +5.5V (doubling charge pump) and -5.5V
(inverting charge pump), over the 3.0V to 5.5V V
range. The charge pump operates in discontinuous
mode; if the output voltages are less than 5.5V, the
charge pump is enabled, and if the output voltages
exceed 5.5V, the charge pump is disabled. Each
charge pump requires a flying capacitor (C1, C2) and a
reservoir capacitor (C3, C4) to generate the V+ and V-
supplies (Figure 1).
The transmitters are inverting level translators that con-
vert CMOS-logic levels to ±5.0V EIA/TIA-232 levels.
The MAX3385E transmitters guarantee a 250kbps data
rate with worst-case loads of 3kΩ in parallel with 1000pF,
providing compatibility with PC-to-PC communication
software (such as LapLink™). Transmitters can be paral-
leled to drive multiple receivers or mice.
Figure 1. Slew-Rate Test Circuits
Laplink is a trademark of Traveling Software.
_______________Detailed Description
±15kV ESD-Protected, 3.0V to 5.5V, Low-Power,
C1
C2
V
CC
V
CC
Dual Charge-Pump Voltage Converter
MINIMUM SLEW-RATE TEST CIRCUIT
0.1µF
SHDN
T_ IN
R_ OUT
C1+
C1-
C2+
C2-
_______________________________________________________________________________________
up to 250kbps, True RS-232 Transceiver
MAX3385E
GND
V
CC
RS-232 Transmitters
5k
T_ OUT
R_ IN
V+
V-
3k
C3
C4
2500pF
3k
CC
The MAX3385E’s transmitters are disabled and the out-
puts are forced into a high-impedance state when the
device is in shutdown (SHDN = GND). The MAX3385E
permits the outputs to be driven up to ±12V in shut-
down.
The transmitter inputs do not have pull-up resistors.
Connect unused inputs to GND or V
The receivers convert RS-232 signals to CMOS-logic
output levels (Table 1).
Supply current falls to less than 1µA in shutdown mode
(SHDN = low). When shut down, the device’s charge
pumps are shut off, V+ is pulled down to V
pulled to ground, and the transmitter outputs are dis-
abled (high impedance). The time required to exit shut-
Table 1. Shutdown Truth Table
C1
C2
V
CC
V
CC
SHDN
0
1
0.1µF
MAXIMUM SLEW-RATE TEST CIRCUIT
SHDN
T_ IN
R_ OUT
C1+
C1-
C2+
C2-
MAX3385E
GND
V
T_OUT
High-Z
Active
CC
5k
RS-232 Receivers
T_ OUT
R_ IN
Shutdown Mode
V+
V-
CC
.
7k
R_OUT
Active
Active
C3
CC
C4
, V- is
150pF
3k
5