
MAX1245
+2.375V, Low-Power, 8-Channel,
Serial 12-Bit ADC
12
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Internal Clock
In internal clock mode, the MAX1245 generates its own
conversion clock internally. This frees the P from the
burden of running the SAR conversion clock and allows
the conversion results to be read back at the proces-
sor’s convenience, at any clock rate from zero to
1.5MHz. SSTRB goes low at the start of the conversion
and then goes high when the conversion is complete.
SSTRB will be low for a maximum of 7.5s (SHDN =
open), during which time SCLK should remain low for
best noise performance.
An internal register stores data when the conversion is
in progress. SCLK clocks the data out of this register at
any time after the conversion is complete. After SSTRB
goes high, the next falling clock edge produces the
MSB of the conversion at DOUT, followed by the
remaining bits in MSB-first format (Figure 9). CS does
not need to be held low once a conversion is started.
Pulling CS high prevents data from being clocked into
the MAX1245 and three-states DOUT, but it does not
adversely affect an internal clock-mode conversion
already in progress. When internal clock mode is
tSDV
tSSTRB
PD0 CLOCKED IN
tSTR
SSTRB
SCLK
CS
tSSTRB
Figure 8. External-Clock-Mode SSTRB Detailed Timing
CS
SCLK
DIN
DOUT
tCSH
tCSS
tCL
tDS
tDH
tDV
tCH
tDO
tTR
tCSH
Figure 7. Detailed Serial-Interface Timing