AN1988 Freescale Semiconductor / Motorola, AN1988 Datasheet - Page 3

• Manufacturer Part Number: AN1988
• Description: AN1988
• Manufacturer: Freescale Semiconductor / Motorola

inductor one can increase the value of just the series resistor.
However one must take into consideration the tradeoffs
involved. In order to get roughly the same improvement in the
PSRR with a 0.5 µF capacitor as there was with the 50 ohm
and 2 µF RC combination one must increase the series
impedence to 150 ohms (see
the PSRR (see
compared with the 50 ohm 2 µF filter. It is still well below unity
for this configuration.
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Freescale Semiconductor
If a smaller capacitance is desired in application with no
This alternate RC circuit produces the following effect on
Figure
7). Notice the similarity in the gain when
Figure
Figure 7. PSRR with 150 Ohm and 0.5 µF Input Capacitance
6).
Figure 5. PSRR with RC and RLC Input Filter
AN1988, Rev 1
Figure 6. Alternate RC Input Loading for PSRR at V
SUPPLY
POWER
150 OHM
0.5 µF
V
dd
MMA6200Q
X
Y
out
out
dd
3