sp332ct-tr Exar Corporation, sp332ct-tr Datasheet - Page 7

• Manufacturer Part Number: sp332ct-tr
• Description: Rs-232/rs-485 Multi-mode Serial Transceiver
• Manufacturer: Exar Corporation

RS-232 Mode
TGoddard/SP332/9617R0
Phase 3
-Vdd charge storage- The third phase of the
clock is identical to the first phase- the trans-
ferred charge in C1 produces -5V in the negative
terminal of C1, which is applied to the negative
side of capacitor C2. Since C2+ is at +5V, the
voltage potential across C2 is 10V.
Phase 4
-Vdd transfer- The fourth phase of the clock
connects the negative terminal of C2 to ground
and transfers the generated 10V across C2 to C4,
the Vdd storage capacitor. Simultaneously with
this, the positive side of capacitor C1 is switched
to +5V and the negative side is connected to
ground, and the cycle begins again.
SP332 TYPICAL OPERATING CIRCUIT
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
0.1 F
0.1 F
0V
0V
21
22
12
11
13
24
26
27
28
19
20
1
8
2
9
TI2
TI3
RX1
RX2
RX3
RX4
C2+
TI1
TI4
C1+
C1-
C2-
SEL A
SEL B
GND
400K
400K
400K
400K
Vcc
Vcc
Vcc
Vcc
SP332
T1
T2
T3
T4
5
VCC
+5V
R2
R3
R4
R1
SHUT
DOWN
5K
5K
5K
5K
LOOP
BACK
TX1
TX2
TX3
TX4
RI2
RI1
RI3
RI4
V+
V-
15
16
17
18
10
14
23
7
25
SP332 RS-232/RS-485 Multi-Mode Serial Transceiver
6
4
3
0.1 F
0.1 F
TTL/CMOS
RS-232
RS-232
RS-232
RS-232
RS-232
RS-232
RS-232
RS-232
TTL/CMOS
7
RS-485 Mode
Since both V+ and V- are separately generated
from Vcc in a no load condition, V+ and V- will
be symmetrical. Older charge pump approaches
that generate V- from V+ will show a decrease
in the magnitude of V- compared to V+ due to
the inherent inefficiencies in the design.
The clock rate for the charge pump typically
operates at 15kHz. The external capacitors must
be 0.1 F with a 16V breakdown rating.
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
TTL/CMOS
0.1 F
0.1 F
+5V
+5V
12
13
11
24
26
27
28
20
22
9
19
21
2
1
8
TI1
TI2
TI3
TI4
RX1
RX2
RX3
RX4
C1+
C1-
C2+
C2-
SEL A
SEL B
GND
400K
400K
Vcc
Vcc
SP332
R1
R3
T1
T3
5
+5V
VCC
© Copyright 2000 Sipex Corporation
15K
15K
SHUT
DOWN
LOOP
BACK
15K
TX1
TX4
TX3
TX2
15K
RI4
RI3
V+
RI2
RI1
V-
10
14
16
18
15
17
3
4
7
6
25
23
0.1 F
RS-485
RS-485
0.1 F
RS-485
RS-485
RS-485
RS-485
RS-485
TTL/CMOS
TTL/CMOS
RS-485