SP3203 Sipex, SP3203 Datasheet - Page 9

• Manufacturer Part Number: SP3203
• Description: 3V RS-232 Serial Transceiver with Logic Selector
• Manufacturer: Sipex

Rev. 6/25/03
duces –V
is applied to the negative side of capacitor C
Since C
C
V
The fourth phase of the clock connects the nega-
tive terminal of C
positive generated voltage across C
V
to +5.5V. At this voltage, the internal oscillator
is disabled. Simultaneous with the transfer of the
voltage to C
switched to V
nected to GND, allowing the charge pump cycle
to begin again. The charge pump cycle will
continue as long as the operational conditions for
the internal oscillator are present.
Since both V
from V
be symmetrical. Older charge pump approaches
that generate V
the magnitude of V
inherent ineffiencies in the design.
The clock rate for the charge pump is typically
operates at 250kHz. The external capacitors are
usually 0.1µF with a 16V breakdown voltage
rating.
V
Current RS-232 serial tranceivers are designed
with fixed 5V or 3.3V TTL input/output voltages
levels. The V
end user to set the TTL input/output voltage
levels independent of V
the main logic bus of system, the TTL input/
output limits and threshold are reset to interface
with the on board low voltage logic circuity.
3
4
3
2
DD
L
DD
V
0 .
5 .
0 .
is 2 times V
Supply Level
C
storage capacitor. This voltage is regulated
Transfer-Phase 4 (Figure 16)
C
o t
o t
o t
C
(
CC
) V
3
5
5
a
2 +
6 .
5 .
5 .
p
CC
, in a no–load condition, V
a
is at V
c
in the negative terminal of C
t i
4
+
L
r o
, positive side of capacitor C
CC
function in the SP3203 allows the
–
C
and V
CC
0
S
from V
1
0
CC
0 .
0
e
2 .
.
and the negative side is con-
(
1 .
2
e l
4
µ ) F
, the voltage potential across
2
–
7
to GND, and transfers this
t c
–
compared to V
o i
are separately generated
+
CC
n
will show a decrease in
T
. By connecting V
C
a
l b
- 2
0
: e
C
0
3 .
1
( 4
1 .
3
µ ) F
+
2
+
and V
to C
due to the
1
, which
4
–
, the
will
1
L
to
is
2
.
9
SP3203
© Copyright 2003 Sipex Corporation