STC3232E Datasheet Rev.0.1, Dec.2005
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STC International Limited
http://www.mcu-memory.com
6
Applications Information
Capacitor Selection
Power-Supply Decoupling
Operation Down to 2.7V
Interconnection with 3V and 5V Logic
Pin Configurations and Typical Operating Circuits
The capacitor type used for C1–C4 is not critical for proper operation; polarized or non-polarized capacitors can be used.
The charge pump requires 0.1µF capacitors for 3.3V operation. Increasing the capacitor values (e.g., by a factor of 2)
reduces ripple on the transmitter outputs and slightly reduces power consumption. C2, C3, and C4 can be increased
without changing C1’s value. When using the minimum required capacitor values, make sure the capacitor value does
not degrade excessively with temperature. If in doubt, use capacitors with a larger nominal value. The capacitor’s
equivalent series resistance (ESR), which usually rises at low temperatures, influences the amount of ripple on V+ and
V- output voltages.
n most circumstances, a 0.1µF VCC bypass capacitor is adequate. In applications sensitive to power-supply noise, use a
capacitor of the same value as charge pump capacitor C1. Connect bypass capacitors as close to the IC as possible.
Transmitter outputs meet EIA/TIA-562 levels of ±3.7V with supply voltages as low as 2.7V.
The STC3232E can directly interface with various 3V and 5V logic families, including ACT and HCT CMOS.
C1+
1
16 Vcc
STC3232E
V+
2
15 GND
C1-
3
14 T1OUT
C2+
4
13 R1IN
C2-
5
12 R1OUT
V-
6
11 T1IN
T2OUT
7
10 V2IN
R2IN
8
9 R2OUT
DIP/SO
+
C1
1
3
4
5
C2
C5
C3
Vcc
16
C1+
C1-
C2+
C2-
V+
V-
2
6
C4
Vcc
STC3232E
Vcc
200KΩ
TTL/CMOS
INPUTS
11
10
T1IN
T2IN
+5V
200KΩ
T1OUT
T2OUT
14
7
RS-232
OUTPUTS
TTL/CMOS
OUTPUTS
12
9
R1OUT
R2OUT
R1IN
5KΩ
R2IN
13
8
RS-232
INPUTS
5KΩ
GND
15
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