MPC555
/
MPC556
QUEUED ANALOG-TO-DIGITAL CONVERTER MODULE-64
MOTOROLA
USER’S MANUAL
Rev. 15 October 2000
13-13
Figure 13-5 Conversion Timing
13.9.1.1 Amplifier Bypass Mode Conversion Timing
If the amplifier bypass mode is enabled for a conversion by setting the amplifier bypass
(BYP) bit in the CCW, the timing changes to that shown in
The buffered
sample time is eliminated, reducing the potential conversion time by two QCLKs. How-
ever, due to internal RC effects, a minimum final sample time of four QCLKs must be
allowed. This results in no savings of QCLKs. When using the bypass mode, the ex-
ternal circuit should be of low source impedance, typically less than 10 k
Ω
. Also, the
loading effects of the external circuitry by the QADC64 need to be considered, since
the benefits of the sample amplifier are not present.
NOTE
Because of internal RC time constants, a sample time of two QCKLs
in bypass mode for high frequency operation is not recommended.
Figure 13-6 Bypass Mode Conversion Timing
BUFFER
SAMPLE
TIME
FINAL SAMPLE
TIME
RESOLUTION
TIME
SAMPLE TIME
SUCCESSIVE APPROXIMATION RESOLUTION
SEQUENCE
2 CYCLES
N CYCLES:
10 CYCLES
QCLK
(2, 4, 8, 16)
SAMPLE
TIME
RESOLUTION
TIME
SAMPLE
TIME
SUCCESSIVE APPROXIMATION RESOLUTION
SEQUENCE
N CYCLES:
10 CYCLES
QCLK
(2, 4, 8, 16)
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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