SP3223EBCA-L/TR Exar Corporation, SP3223EBCA-L/TR Datasheet - Page 11

• Manufacturer Part Number: SP3223EBCA-L/TR
• Description: Intelligent +3.0V To +5.5V RS-232 Transceivers
• Manufacturer: Exar Corporation
• Type: Transceiverr

Specifications of SP3223EBCA-L/TR

• Number Of Drivers/receivers: 2/2
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 20-SSOP (0.200", 5.30mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

pump that provides output voltages of
+/-5.5V regardless of input voltage (V
over the +3.0V to +5.5V range.
is important to maintain compliant RS-
232 levels regardless of power supply
fluctuations.
The charge pump operates in a discontinu-
ous mode using an internal oscillator. If the
output voltages are less than a magnitude
of 5.5V, the charge pump is enabled. If the
output voltages exceed a magnitude of 5.5V,
the charge pump is disabled. This oscillator
controls the four phases of the voltage shift-
ing. A description of each phase follows.
Phase 1
— V
of the clock cycle, the positive side of capaci-
tors C
C
in C
nected to V
capacitor C
Phase 2
— V
connects the negative terminal of C
storage capacitor and the positive terminal of
C
ated voltage to C
regulated to a minimum voltage of -5.5V.
Simultaneous with the transfer of the volt-
age to C
is switched to V
connected to GND.
Phase 3
— V
the clock is identical to the first phase — the
charge transferred in C
the negative terminal of C
to the negative side of capacitor C
C
is 2 times V
Phase 4
— V
the clock connects the negative terminal
of C
generated voltage across C
V
DD
l
2
2
+
+
to GND. This transfers a negative gener-
is then switched to GND and the charge
is at V

SS
DD
2
–
SS
storage capacitor.
DD
is transferred to C

to GND, and transfers this positive
charge storage — During this phase
charge storage — The third phase of
transfer — Phase two of the clock
and C
transfer — The fourth phase of
3
, the positive side of capacitor C
CC
2
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (50)668-707 • www.exar.com
, the voltage potential across C
CC
CC
is now 2 times V
, the voltage potential across
.
2
are initially charged to V
CC
3
. This generated voltage is
and the negative side is
2

–
. Since C

produces –V
, which is applied
This voltage is
CC
2
.
to C
2
to the V
2
2
+
. Since
is con-
4
, the
CC
This
CC
CC
SS
in
)

2
.

regulated to +5.5V. At this voltage, the in-
ternal oscillator is disabled. Simultaneous
with the transfer of the voltage to C
positive side of capacitor C
and the negative side is switched to GND, al-
lowing 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
ated from V
and V
pump approaches that generate V
V
of V
inefficiencies in the design.
AUTO ON-LINE
The SP3223 devices have a patent pend-
ing AUTO ON-LINE
that saves power in applications such as
laptop computers, PDA's, and other portable
systems.
The SP3223 devices incorporate an AUTO
ON-LINE
itself when the external transmitters are
enabled and the cable is connected. Con-
versely, the AUTO ON-LINE
disables most of the internal circuitry when
the device is not being used and goes into
a standby mode where the device typically
draws µA. This function can also be exter-
nally controlled by the ONLINE pin. When
this pin is tied to a logic LOW, the AUTO
ON-LINE
the device is enabled until there is no activity
on the receiver inputs. The receiver input
typically sees at least ±3V, which are gener-
ated from the transmitters at the other end
of the cable with a ±5V minimum. When
the external transmitters are disabled or the
cable is disconnected, the receiver inputs
will be pulled down by their internal 5kΩ
resistors to ground. When this occurs over
a period of time, the internal transmitters
will be disabled and the device goes into
a shutdown or standby mode. When the
+
will show a decrease in the magnitude
–
–
compared to V
will be symmetrical. Older charge
®
®
circuit that automatically enables
function is active. Once active,
CC
+
and V
, in a no–load condition V
®
Circuitry
–
are separately gener-
®
+
due to the inherent
circuitry on board
SP3223E/EB/EU_00_20

is switched to V
®
circuit also
–
4
, the
from
CC
+