Rainbow Electronics MAX1299 - Manual (Page 15)

MAX1298/MAX1299
12-Bit Serial-Output Temperature Sensors
with 5-Channel ADC
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Reference Selection
Select between internal and external voltage modes
through bit REF of the configuration byte. Set REF = 1
for internal reference mode and REF = 0 for external
reference mode.
Internal Reference
The MAX1298 has a 2.50V internal reference, while the
MAX1299 has a 1.20V internal reference. Both are fac-
tory trimmed for accuracy. When internal reference is
selected, REF can be used to drive an external load
with 100µA capability. Bypass REF to GND with a 0.1µF
(min) capacitance. Wake-up time is C x 2.5 x 10
4 s for
the MAX1298 and C x 1.2 x 10 4 s for the MAX1299.
External Reference
The MAX1298 can directly accept reference voltages at
REF from 0.8V to 2.5V, while the MAX1299 can directly
accept reference voltages from 0.8V to 1.2V. Bypass
REF to GND with a 0.1µF capacitor. Temperature mea-
surements always use internal reference.
Power Modes
The MAX1298 (MAX1299) typically requires supply cur-
rents of 380µA (350µA) or 310µA (280µA) when per-
forming voltage conversions at 100% duty cycle with
internal or external references, respectively. The differ-
Table 1. Output Data Format
Table 2. Configuration-Byte Format
D11 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0 S0 0 0
BIT 7
(MSB)
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1
BIT 0
(LSB)
Start 0 0 0 0 PM1 PM0 REF
BIT NAME DESCRIPTION
7 (MSB) Start First logic 1 after CS goes low. (See Input Data Format.)
6, 5, 4, 3 Must be 0000 to load a configuration byte.
2, 1 PM1, PM0 These 2 bits select the desired power mode (Table 4).
0 REF A logic high enables the internal reference. A logic low disables the internal reference and
selects the external reference mode.
Table 3. Conversion-Byte Format
BIT 7
(MSB)
BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1
BIT 0
(LSB)
Start 0 1 0 SEL3 SEL2 SEL1 SEL0
BIT NAME DESCRIPTION
7 (MSB) Start First logic 1 after CS goes low. (See Input Data Format.)
6, 5, 4 Must be 010 to load a conversion byte.
3, 2, 1, 0
SEL3, SEL2,
SEL1, SEL0
These 4 bits select the input configuration (Table 5).
Figure 6. Detailed SSTRB Timing
t CSH
t DO
t SSTRB
t
CONV
t SCK
t CSS
CSB
SSTRB
SCLK
DOUT
PDO CLOCKED IN
SSTRB TIMING