LT1461 LINER [Linear Technology], LT1461 Datasheet - Page 7

• Manufacturer Part Number: LT1461
• Description: Easy-to-Use, Ultra-Tiny, Differential, 16-Bit ADC With I2C Interface
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
CONVERTER OPERATION
Converter Operation Cycle
The LTC2453 is a low-power, fully differential, delta-sigma
analog-to-digital converter with an I
tion, as shown in Figure 1, is composed of three successive
states: CONVERSION, SLEEP and DATA OUTPUT.
Initially, at power up, the LTC2453 performs a conversion.
Once the conversion is complete, the device enters the
sleep state. While in this sleep state, power consumption is
reduced by several orders of magnitude. The part remains
in the sleep state as long it is not addressed for a read
operation. The conversion result is held indefi nitely in a
static shift register while the part is in the sleep state.
The device will not acknowledge an external request during
the conversion state. After a conversion is fi nished, the
device is ready to accept a read request. The LTC2453’s
address is hard-wired at 0010100. Once the LTC2453 is
addressed for a read operation, the device begins output-
ting the conversion result under the control of the serial
clock (SCL). There is no latency in the conversion result.
The data output is 16 bits long and contains a 15-bit plus
sign conversion result. Data is updated on the falling
Figure 1. LTC2453 State Diagram
2453 F01
NO
NO
POWER-ON RESET
ACKNOWLEDGE
DATA OUTPUT
CONVERSION
OR READ
16-BITS
SLEEP
READ
STOP
YES
YES
2
C interface. Its opera-
edges of SCL, allowing the user to reliably latch data on
the rising edge of SCL. A new conversion is initiated by
a stop condition following a valid read operation, or by
the conclusion of a complete read cycle (all 16 bits read
out of the device).
Power-Up Sequence
When the power supply voltage (V
verter is below approximately 2.1V, the ADC performs a
power-on reset. This feature guarantees the integrity of
the conversion result.
When V
generates an internal power-on reset (POR) signal for
approximately 0.5ms. The POR signal clears all internal
registers. Following the POR signal, the LTC2453 starts
a conversion cycle and follows the succession of states
described in Figure 1. The fi rst conversion result fol-
lowing POR is accurate within the specifi cations of the
device if the power supply voltage V
the operating range (2.7V to 5.5V) before the end of the
POR time interval.
Ease of Use
The LTC2453 data output has no latency, fi lter settling delay
or redundant results associated with the conversion cycle.
There is a one-to-one correspondence between the conver-
sion and the output data. Therefore, multiplexing multiple
analog input voltages requires no special actions.
The LTC2453 performs offset calibrations every conver-
sion. This calibration is transparent to the user and has
no effect upon the cyclic operation described previ-
ously. The advantage of continuous calibration is extreme
stability of the ADC performance with respect to time and
temperature.
The LTC2453 includes a proprietary input sampling scheme
that reduces the average input current by several orders
of magnitude when compared to traditional delta-sigma
architectures. This allows external fi lter networks to in-
terface directly to the LTC2453. Since the average input
sampling current is 50nA, an external RC lowpass fi lter
using a 1kΩ and 0.1μF results in <1LSB additional error.
Additionally, there is negligible leakage current between
IN
+
and IN
CC
–
.
rises above this threshold, the converter
CC
CC
) applied to the con-
is restored within
LTC2453
7
2453f