Rev. 6/25/03

SP3203

© Copyright 2003 Sipex Corporation

8

consists of a regulated dual charge pump that

provides output voltages of 5.5V regardless of

range. This is important to maintain compliant

RS-232 levels regardless of power supply

fluctuations.

The charge pump operates in a discontinuous

mode using an internal oscillator. If the output

voltages are less than a of 5.5V, the charge

pump is enabled. If the output voltages exceed

a of 5.5V, the charge pump is disabled. This

oscillator controls the four phases of the voltage

shifting (Figure 12). A description of each phase

follows.

During this phase of the clock cycle, the positive

Table 1. SHUTDOWN Truth Table.

(Note: When device in shutdown, the SP3203's charge pump is turned off

and V+ decays to V

are disabled as High Impendance).

Figure 9. Loopback Test Circuit for RS-232 Driver Data

Transmission Rates

Phase two of the clock connects the negative

This generated voltage is

regulated to a minimum voltage of -5.5V.

Simultaneous with the transfer of the voltage

connected to GND.

The third phase of the clock is identical to the

Figure 10. Loopback Test Circuit Result at 120Kbps

(All Drivers Fully Loaded)

Figure 11. Loopback Test Circuit result at 250Kbps

(All Drivers Fully Loaded)

SP3203

1

3

5

4

2

6

19

GND

T

T

C1+

C1-

C2+

C2-

V+

V-

0.1µF

0.1µF

0.1µF

+

C2

C5

C1

+

+

C3

C4

+

+

0.1µF

0.1µF

TTL/CMOS

INPUTS

+3V to +5V

18

SHUTDOWN

20

5KΩ

R

5KΩ

R

R

TTL/CMOS

OUTPUTS

R

T

T

1000pF

1000pF

12

V L

+3V to +5.5V

Ch1

Ch3

3

1

2

T

T

T

T

[]

T1 IN

T1 OUT

R1 OUT

5.00V

Ch2 5.00V M 5.00µs Ch1

0V

5.00V

3

1

2

T

T

T

T

[]

T1 IN

T1 OUT

R1 OUT

Ch1

Ch3

5.00V

Ch2 5.00V M 2.50µs Ch1

0V

5.00V

3

0

2

3

P

S

:

E

C

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D

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T

U

H

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OR

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Oe

g

r

a

h

C

p

m

u

P

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h

g

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-

h

g

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v

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t

c

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