SP3223E_06 Datasheet, PDF (15/23 Pages) Sipex Corporation – Intelligent +3.0V to +5.5V RS-232 Transceivers

The Sipex-patented charge pumps are designed
to operate reliably with a range of low cost
capacitors.Either polarized or non polarized
capacitors may be used. If polarized capacitors
are used they should be oriented as shown in the
Typical Operating Circuit. The V+ capacitor
may be connected to either ground or Vcc
(polarity reversed.)
The charge pump operates with 0.1µF capacitors
for 3.3V operation. For other supply voltages,
see the table for required capacitor values. Do
not use values smaller than those listed.
Increasing the capacitor
values (e.g., by doubling in value) reduces
ripple on the transmitter outputs and may slightly
reduce power consumption. C2, C3, and C4 can
be increased without changing C1’s value
For best charge pump efficiency locate the charge
pump and bypass capacitors as close as possible
to the IC. Surface mount capacitors are best for
this purpose. Using capacitors with lower
equivalent series resistance (ESR) and self-
inductance, along with minimizing parasitic PCB
trace inductance will optimize charge pump
operation. Designers are also advised to consider
that capacitor values may shift over time and
operating temperature.
Minimum recommended charge pump capacitor value
Input Voltage V_CC
3.0V to 3.6V
4.5V to 5.5V
3.0V to 5.5V
Charge pump capacitor value for SP32XX
C1 – C4 = 0.1uF
C1 = 0.047uF, C2-C4 = 0.33uF
C1 – C4 = 0.22uF
Date: 10/06/06
SP3223 +3.0V to +5.5V RS-232 Transceivers
15
© Copyright 2006 Sipex Corporation