SP3238EE Datasheet, PDF (8/20 Pages) Sipex Corporation – Intelligent +3.0V to +5.5V RS-232 Transceiver

DESCRIPTION
The SP3238EE device meets the EIA/TIA-232
and ITU-T V.28/V.24 communication protocols
and can be implemented in battery-powered,
portable, or hand-held applications such as
notebook or palmtop computers. The SP3238E
device features Sipex's proprietary and patented
(U.S. #5,306,954) on-board charge pump
circuitry that generates ±5.5V RS-232 voltage
levels from a single +3.0V to +5.5V power
supply. The SP3238E device can guarantee a
data rate of 250kbps fully loaded.
The SP3238EE is a 5-driver/3-receiver device,
ideal for portable or hand-held applications.
The SP3238EE includes one complementary
always-active receiver that can monitor an
external device (such as a modem) in shutdown.
This aids in protecting the UART or serial
controller IC by preventing forward biasing
of the protection diodes where V_CC may be
disconnected.
VCC
UART
or
Serial µC
+
C5 0.1µF
28 _C1+
+
C1 0.1µF
25 C1-
1 C2+
+
C2 0.1µF
3 C2-
RxD
24 T1IN
CTS
23 T2IN
DSR
22 T3IN
DCD
19 T4IN
RI
17 T5IN
26
VCC
27
V+
+
C3 0.1µF
SP3238EE _V- 4
T₁OUT ₅
T₂OUT 6
T₃OUT 7
T₄OUT 10
T₅OUT 12
C4 0.1µF
+
RS-232
OUTPUTS
TxD
RTS
DTR
VCC
16 ^R1^OUT
21 R1OUT
20 R2OUT
18 ^R3^OUT
R₁IN ₈
5kΩ
R₂IN 9
5kΩ
R₃IN 11
5kΩ
14
SHUTDOWN
13 _ONLINE
15 _STATUS
GND
2
RS-232
INPUTS
RESET
µP
Supervisor
VIN
IC
Figure 6. Interface Circuitry Controlled by
Microprocessor Supervisory Circuit
The SP3238EE device is an ideal choice for
power sensitive designs. The SP3238EE device
features AUTO ON-LINE^® circuitry which re-
duces the power supply drain to a 1µA supply
current. In many portable or hand-held applica-
tions, an RS-232 cable can be disconnected or a
connected peripheral can be turned off. Under
these conditions, the internal charge pump and
the drivers will be shut down. Otherwise, the
system automatically comes online. This feature
allows design engineers to address power saving
concerns without major design changes.
THEORY OF OPERATION
The SP3238EE device is made up of four basic
circuit blocks: 1. Drivers, 2. Receivers,
3. the Sipex proprietary charge pump, and
4. AUTO ON-LINE^® circuitry.
Drivers
The drivers are inverting level transmitters that
convert TTL or CMOS logic levels to 5.0V EIA/
TIA-232 levels with an inverted sense relative to
the input logic levels. Typically, the RS-232
output voltage swing is +5.4V with no load and
+5V minimum fully loaded. The driver outputs
are protected against infinite short-circuits to
ground without degradation in reliability. These
drivers comply with the EIA-TIA-232F and all
previous RS-232 versions.
The drivers can guarantee a data rate of 250kbps
fully loaded with 3kΩ in parallel with 1000pF,
ensuring compatibility with PC-to-PC commu-
nication software. All unused driver inputs must
be connected to V_CC or GND.
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,
Paragraph 5). The transition of the loaded
output from HIGH to LOW also meets the
monotonicity requirements of the standard.
Date: 02/24/05
SP3238EE Intelligent +3.0V to +5.5V RS-232 Transceiver
8
© Copyright 2005 Sipex Corporation