Datasheet
ADS7229
ADS7230
SBAS437A – MAY 2008 – REVISED JUNE 2009 ...............................................................................................................................................................
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Auto Nap Mode
Auto nap mode is almost identical to nap mode. The only difference is the time when the device is actually
powered down and the method used to wake up the device. Configuration register bit D4 is only used to
enable/disable Auto nap mode. If Auto nap mode is enabled, the device turns off the biasing after the conversion
has finished; that is, the end of conversion activates Auto nap power-down mode. Supply current falls from
5.7mA in normal mode to about 0.3mA in 200ns. A CONVST command resumes the device and turns on the
biasing on again in 3 CCLKs (143ns with a 21MHz conversion clock). The device can also be woken up by
disabling auto nap mode when bit D4 of the configuration register is set to '1'. Any channel select command
0XXXb, a wake-up command, or the set default mode command 1111b can also wake up the device from Auto
nap power-down. Table 2 compares the various power-down modes.
NOTE:
1. This wake-up command is the word 1011b in the command word. This command sets bits
D2 and D3 to '1' in the configuration register, but not D4. A wake-up command removes
the device from any of these power-down states, Deep/Nap/Auto nap power-down.
2. Wake-up time is defined as the time between when the host processor tries to wake up the
converter and when a conversion start can occur.
Table 2. Power-Down Mode Comparisons
SUPPLY TIME TO
TYPE OF CURRENT POWER-DOWN WAKE-UP
POWER-DOWN AT 5V/3V ACTIVATED BY (ns) WAKE-UP BY TIME ENABLE
Normal operation 5.7mA/4.5mA
Deep power-down 4nA/1nA Setting CFR 100 Woken up by command 1011b 1 µ s Set CFR
Nap power-down 0.3mA/0.25mA Setting CFR 200 Woken up by command 1011b 3 CCLKs Set CFR
Woken up by CONVST, any channel
Auto nap EOC (end of
0.3mA/0.25mA 200 select command, default command 3 CCLKs Set CFR
power-down conversion)
1111b, or wake up command 1011b.
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