SH7014 Datasheet, PDF (428/754 Pages) Renesas Technology Corp – 32-Bit RISC Microcomputer

13. High Speed A/D Converter ⎯ SH7014 ⎯
13.6 Usage Notes
Note the following points concerning the high speed A/D converter.
13.6.1 Analog Input Voltage Range
During A/D conversions, see that the voltage applied to the analog input pins AN0 to AN7 is
within the range of AV_SS ≤ AN0 to AN7 ≤ AV_CC.
13.6.2 AV_CC, AV_SS Input Voltages
The AV_CC, AV_SS input voltages should be AV_CC = V_CC ±10%, and AV_SS = V_SS. When not using the
high speed A/D converter, make AV_CC = V_CC and AV_SS = V_SS. When in standby mode, make V_RAM ≤
AV_CC ≤ 5.5 V, and AV_SS = V_SS. V_RAM is the RAM standby voltage.
13.6.3 Input Ports
Make the time constant of circuitry connected to an input port shorter than the high speed A/D
converter sampling time. If the time constant of the circuit is longer, there will be occasions where
the input voltage is not adequately sampled.
13.6.4 Conversion Start Modes
Current consumption will be different for the A/D conversion operation in high speed start mode
and low-power conversion mode according to the PWR bit setting.
13.6.5 A/D Conversion Termination (HD6417014R only)
If conversion is terminated while in progress (when ADST = 1) in high-speed start mode (PWR =
1) by clearing the ADST bit, there may be a large degree of error in the first conversion following
the restart (on channel 1 in normal mode, or channel 2 in simultaneous sampling mode).
Subsequent conversions will be performed normally
If A/D conversion is terminated while in progress, use one of the following methods to solve this
problem:
(a) Ignore the first data following a restart after termination.
(b) If the first data after a restart is used, perform a single dummy conversion in single mode after
the termination, terminate A/D conversion, then restart.
(c) After termination, write 0 to the PWR bit before restarting. (In this case, the first conversion
after the restart will begin after the elapse of 200 A/D reference clock cycles.)
Rev.5.00 Sep. 27, 2007 Page 394 of 716
REJ09B0398-0500