+5V INPUT
+5V INPUT
7
7
V
V
CC
CC
400k
Ω
Ω
2
5
400k
Ω
Ω
2
5
T
IN
IN
T
OUT
T
T
IN
IN
T
OUT
T
1
1
1
1
1
1
400k
1
3
18
4
400k
1
3
18
4
T
T
OUT
IN
T
T
T
OUT
IN
T
2
2
1
2
2
2
1
2
R
R
OUT
R
R
R
R
OUT
R
R
1
1
1
1
5kΩ
5kΩ
5kΩ
5kΩ
20
19
20
19
OUT
R
IN
R
OUT
R
IN
R
2
2
2
2
2
2
8
13
14
10
C
C
+
-
C
C
+
-
Do not make
connection to
these pins
1
Do not make
connection to
these pins
1
13
12
11
12
C
C
C
C
+
+
-
1
C
C
C
C
+
+
-
2
2
1
2
2
15
10
16
15
11
16
Internal
-10V Power
Supply
V-
V-
V+
Internal
-10V Power
Supply
V-
V-
V+
17
14
17
8
2
2
2
2
Internal
+10V Power
Supply
SP233A
GND
Internal
+10V Power
Supply
SP233ACT
GND GND
-
GND
-
6
9
6
9
Figure 4. Typical Circuits using the SP233ACP and SP233ACT
After the ring indicator signal has propagated
through the SP312A receiver, it can be used to
trigger the power management circuitry of the
computer to power up the microprocessor, and
bring the SD pin of the SP312A to a logic high,
takingitoutoftheshutdownmode. Thereceiver
propagation delay is typically 1µs. The enable
timeforV+ andV– istypically2ms. AfterV+ and
V– have settled to their final values, a signal can
be sent back to the modem on the data terminal
ready (DTR) pin signifying that the computer is
ready to accept and transmit data.
Shutdown (SD) and Enable (EN)
SP310A/SP312A Only
BoththeSP310AandSP312Ahaveashut-down/
standby mode to conserve power in battery-pow-
ered systems. To activate the shutdown mode,
which stops the operation of the charge pump, a
logic “0” is applied to the appropriate control line.
For the SP310A, this control line is ON/OFF (pin
18). Activating the shutdown mode also puts the
SP310A transmitterandreceiveroutputsinahigh
impedance condition (tri-stated). The shutdown
mode is controlled on the SP312A by a logic “0”
ontheSHUTDOWNcontrolline(pin18);thisalso
puts the transmitter outputs in a tri–state mode.
The receiver outputs can be tri–stated separately
during normal operation or shutdown by a logic
“1” on the ENABLE line (pin 1).
Pin Strapping — SP233ACT Only
The SP233A packaged in the 20–pin SOIC
package (SP233ACT) has a slightly different
pinout than the SP233A in other package
configurations.Tooperateproperly,thefollowing
pairs of pins must be externally wired together:
Wake–Up Feature (SP312A Only)
The SP312A has a wake–up feature that keeps
all the receivers in an enabled state when the
device is in the shutdown mode. Table 1 defines
the truth table for the wake–up function.
the two V– pins (pins 10 and 17)
the two C2+ pins (pins 12 and 15)
the two C2– pins (pins 11 and 16)
All other connections, features, functions and
performance are identical to the SP233A as
specified elsewhere in this data sheet.
With only the receivers activated, the SP312A
typically draws less than 5µA supply current
(10µA maximum). In the case of a modem
interfaced to a computer in power down mode,
the Ring Indicator (RI) signal from the modem
would be used to "wake up" the computer,
allowing it to accept data transmission.
Power
Up/Down
Receiver
Outputs
SD
0
EN
0
Down
Down
Up
Enable
Tri–state
Enable
0
1
1
0
1
1
Up
Tri–state
Table 1. Wake-up Function Truth Table.
SP231ADS/01
SP231A Enhanced RS-232 Line Drivers/Receivers
© Copyright 2000 Sipex Corporation
6
SIPEX [ SIPEX CORPORATION ]
