AN1988 Freescale Semiconductor / Motorola, AN1988 Datasheet - Page 4

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

voltage drop at the input of the device. However, it could be
reduced some and still achieve less than unity gain. With the
same voltage at the input of the filter the output voltage of the
device is lowered. In this case it drops by roughly 5 percent. In
turn, this loss in DC voltage also lowers the ratio-metric error.
However if the voltage at Vdd is allowed to drop much lower
than 2.7 volts the device may not operate at all. If cost and
space permits, one should consider, as stated previously, the
substitution of a series inductor in place of at least part of this
series resistance. This can greatly decrease the DC voltage
drop problem.
harmonic we have X = 2*pie*(15 KHz)*L = 150 ohm. Solving
for L gives the somewhat large value of 1.6 mH for the
4
As stated before this large value of resistance creates a DC
To get a 150 ohm impedance at the frequency of the first
AN1988, Rev 1
inductor. A 1 mH inductor at 15 KHz has an impedance of
about 95 ohms and these devices can be had in quantity
(1000 or more) for less then twenty cents each.
RC and possibly L components to correct power supply
rejection ratio issues caused by noisy power supply lines. This
may not be of concern in many applications; however, it may
be in some. The preceding gives an introduction to power
supply rejection ratio as well as some information to better
understand this potential problem. Also included are some
example filters, the effects on PSRR, as well as suggested
choices.
The MMA6200Q series family of devices require external
CONCLUSION
Freescale Semiconductor
Sensor Products