LTC2983C View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC2983C' PDF : 72 Pages View PDF
LTC2983
Applications Information
The LTC2983 combines high accuracy with ease of use.
The basic operation is simple and is composed of five
states (see Figure 3).
POWER-UP,
SLEEP
OR RESET
START-UP
≈ 200ms(MAX)
CHANNEL ASSIGNMENT
applicable). The user is locked out of RAM access while
in the state (except for reading status location 0x000).
The end of conversion is indicated by both the INTER-
RUPT pin going HIGH and a status register START bit
going LOW and DONE bit going HIGH.
5. Read Results. In this state, the user has access to
RAM and can read the completed conversion results
and fault status bits. It is also possible for the user to
modify/append the channel assignment data during the
read results state.
INITIATE CONVERSION
CONVERSION
Conversion State Details
State 1: Start-Up
(OPTIONAL)
STATUS CHECK NO
COMPLETE?
YES
READ RESULTS
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Figure 3. Basic Operation
The start-up state automatically occurs when power is ap-
plied to the LTC2983. If the power drops below a threshold
of ≈2.6V and then returns to the normal operating voltage
(2.85V to 5.25V), the LTC2983 resets and enters the power-
up state. Note that the LTC2983 also enters the start-up
state at the conclusion of the sleep state. The start-up state
can also be entered at any time during normal operation
by pulsing the RESET pin low.
Conversion States Overview
1. Start-Up. After power is applied to the LTC2983
(VDD > 2.6V), there is a 200ms wake up period. During
this time, the LDO, charge pump, ADCs, and reference
are powered up and the internal RAM is initialized. Once
start-up is complete, the INTERRUPT pin goes HIGH
and the command status register will return a value of
0x40 (Start bit = 0, Done bit = 1) when read.
2. Channel Assignment. The device automatically enters
the channel assignment state after start-up is complete.
While in this state, the user writes sensor specific data
for each input channel into RAM. The assignment data
contains information about the sensor type, pointers to
cold junction sensors or sense resistors, and sensor
specific parameters.
3. Initiate Conversion. A conversion is initiated by writing
a measurement command into RAM memory location
0x000. This command is a pointer to the channel in
which the conversion will be performed.
In the first phase of the start-up state all critical analog
circuits are powered up. This includes the LDO, reference,
charge pump and ADCs. During this first phase, the com-
mand status register will be inaccessible to the user. This
phase takes a maximum of 100mS to complete. Once this
phase completes, the command status register will be
accessible and return a value of 0x80 until the LTC2983
is completely initialized. Once the LTC2983 is initialized
and ready to use, the interrupt pin will go high and the
command status register will return a read value of 0x40
(Start bit = 0, Done bit = 1). At this point the LTC2983
is fully initialized and is ready to perform a conversion.
State 2: Channel Assignment
The LTC2983 RAM can be programmed with up to 20 sets
of 32-bit (4-byte) channel assignment data. These reside
sequentially in RAM with a one-to-one correspondence
to each of the 20 analog input channels (see Table 3).
Channels that are not used should have their channel
assignment data set to all zeros (default at START-UP).
4. Conversion. A new conversion begins automatically
following an Initiate Conversion command. In this state,
the ADC is running a conversion on the specified chan-
nel and associated cold junction or RSENSE channel (if
The channel assignment data contains all the necessary
information associated with the specific sensor tied to that
channel (see Table 4). The first five bits determine the sensor
type (see Table 5). Associated with each sensor are sensor
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For more information www.linear.com/LTC2983
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