SP232AET-L/TR Exar Corporation, SP232AET-L/TR Datasheet - Page 5

• Manufacturer Part Number: SP232AET-L/TR
• Description: 5V Single-Supply RS-232 Drivers/Receivers
• Manufacturer: Exar Corporation
• Type: Transceiverr

Specifications of SP232AET-L/TR

• Number Of Drivers/receivers: 2/2
• Protocol: RS232
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (0.300", 7.50mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Phase 4
Vdd transfer. The fourth phase connects the
negative terminal of C2 to ground and the posi-
tive terminal of C2 to the Vdd storage capacitor .
This transfers the doubled (V+) voltage onto C3.
Meanwhile, capacitor C is charged from Vcc to
prepare it for its next phase.
Under lightly loaded conditions, the intelligent
pump oscillator maximizes efficiency by running
only as needed to maintain V+ and V- voltage
levels. Since interface transceivers spend most
of their time at idle, this power-efficient innova-
tion can greatly reduce total power consump-
tion. This improvement is made possible by
the independent phase sequences of the Exar
charge pump design.
Figure . Charge pump phases
Exar Corporation 48720 Kato Road, Fremont CA, 94538 • (50)668-7000 • Fax (50)668-707 • www.exar.com
C
1
+
+
-
V
CC
Phases 1 and 3: Store/Double.
Double charge from C 1 onto C2.
C 2 is now charged to -2xVcc
C
2
e
e
-
-
+
V+
V-
+
+
C
C
3
4
5
The clock rate of the charge pump typically op-
erates greater than 70kHz allowing the pump to
operate efficiently with small 0.1uF capacitors.
Efficient operation depends on rapid charging
and discharging of C and C2. Therefore, the
capacitors should be mounted as close as pos-
sible to the IC and have a low ESR (equivalent
series resistance). Inexpensive, surface mount
ceramic capacitors are ideal for use on charge
pump. If polarized capacitors are used the posi-
tive and negative terminals should be connect-
ed as shown on the typical operating circuit. A
diagram of the 4 individual phases is shown in
Figure .
Patented 5,306,954
C
C
1
1
e
-
e
-
+
+
+
+
-
V
-
V
CC
CC
Meanwhile C1 is charged to Vcc
Phase 2 – Vss transfer from C2 to C4.
Meanwhile C 1 is charged to Vcc
Phase 4 V
C
C
2
2
DD
e
V
+
+
+
Vss
DD
e
transfer from C2 to C3.
-
e
DESCRiPTion
+
V+
V+
V-
e
-
SP232A_00_05308
+
+
+
+
C
C
C
C
3
4
3
4