SP3222EUCY-L/TR Exar Corporation, SP3222EUCY-L/TR Datasheet - Page 10

• Manufacturer Part Number: SP3222EUCY-L/TR
• Description: 1Mbps, 3.0V To 5.5V RS-232 2-driver/2-receiver, Low-power Shutdown
• Manufacturer: Exar Corporation
• Type: Transceiverr

Specifications of SP3222EUCY-L/TR

• Number Of Drivers/receivers: 2/2
• Protocol: RS232
• Voltage - Supply: 3 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 20-TSSOP (0.173", 4.40mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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
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
DD
l
2
2
+
+
to GND. This transfers a negative gener-
is then switched to GND and the charge
is at V
1
DD
SS
–
2
SS
storage capacitor.
DD
is transferred to C
1
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
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com
2
CC
, the voltage potential across C
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
1
–
. Since C
produces –V
1
, which is applied
This voltage is
1
CC
2
is switched
.
to C
2
to the V
2
2
+
. Since
is con-
4
4
, the
, the
CC
CC
SS
in
1
2
.
10
to V
nected to GND, allowing
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.
The clock rate for the charge pump typically
operates at greater than 250kHz. The exter-
nal capacitors can be as low as 0.1µF with
a 16V breakdown voltage rating.
+
will show a decrease in the magnitude
–
CC
–
compared to V
and
will be symmetrical. Older charge
CC
+
and V
the
, in a no–load condition V
SP3222EU/SP3232EU_100_120810
–
negative side is con-
are separately gener-
+
due to the inherent
DESCRIPTION
the charge
–
from
+