LTC2400IS8 Linear Technology, LTC2400IS8 Datasheet - Page 11

• Manufacturer Part Number: LTC2400IS8
• Description: IC A/D CONV 24BIT MICRPWR 8-SOIC
• Manufacturer: Linear Technology

Specifications of LTC2400IS8

• Mfg Application Notes: Application Note
• Number Of Bits: 24
• Sampling Rate (per Second): 7.5
• Data Interface: MICROWIRE™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 1mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIONS
For large values of V
absolute maximum voltage range of – 0.3V to (V
Beyond this range the input ESD protection devices begin
to turn on and the errors due to the input leakage current
increase rapidly.
Input signals applied to V
– 300mV and above V
fault current, a resistor of up to 5k may be added in series
with the V
device. In the physical layout, it is important to maintain
the parasitic capacitance of the connection between this
series resistance and the V
therefore, the resistor should be located as close as
practical to the V
on the converter accuracy can be evaluated from the
curves presented in the Analog Input/Reference Current
section. In addition a series resistor will introduce a
temperature dependent offset error due to the input leak-
age current. A 1nA input leakage current will develop a
1ppm offset error on a 5k resistor if V
has a very strong temperature dependency.
Output Data Format
The LTC2400 serial output data stream is 32 bits long. The
first 4 bits represent status information indicating the
sign, input range and conversion state. The next 24 bits are
the conversion result, MSB first. The remaining 4 bits are
sub LSBs beyond the 24-bit level that may be included in
averaging or discarded without loss of resolution.
V
CC
–1/8V
IN
9/8V
1/2V
+ 0.3V
–0.3V
V
pin without affecting the performance of the
REF
REF
REF
REF
0
Figure 2. LTC2400 Input Range
IN
pin. The effect of the series resistance
U
NORMAL
RANGE
INPUT
CC
REF
INFORMATION
by 300mV. In order to limit any
IN
U
this range is limited by the
may extend below ground by
EXTENDED
IN
RANGE
INPUT
pin as low as possible;
W
REF
ABSOLUTE
MAXIMUM
RANGE
INPUT
= 5V. This error
2400 F02
CC
U
+ 0.3V).
Bit 31 (first output bit) is the end of conversion (EOC)
indicator. This bit is available at the SDO pin during the
conversion and sleep states whenever the CS pin is LOW.
This bit is HIGH during the conversion and goes LOW
when the conversion is complete.
Bit 30 (second output bit) is a dummy bit (DMY) and is
always LOW.
Bit 29 (third output bit) is the conversion result sign indi-
cator (SIG). If V
bit is LOW. The sign bit changes state during the zero code.
Bit 28 (forth output bit) is the extended input range (EXR)
indicator. If the input is within the normal input range
0 V
normal input range, V
The function of these bits is summarized in Table 1.
Table 1. LTC2400 Status Bits
Input Range
V
0 < V
V
V
Bit 27 (fifth output bit) is the most significant bit (MSB).
Bits 27-4 are the 24-bit conversion result MSB first.
Bit 4 is the least significant bit (LSB).
Bits 3-0 are sub LSBs below the 24-bit level. Bits 3-0 may
be included in averaging or discarded without loss of
resolution.
Data is shifted out of the SDO pin under control of the serial
clock (SCK), see Figure 3. Whenever CS is HIGH, SDO
remains high impedance and any SCK clock pulses are
ignored by the internal data out shift register.
In order to shift the conversion result out of the device, CS
must first be driven LOW. EOC is seen at the SDO pin of the
device once CS is pulled LOW. EOC changes real time from
HIGH to LOW at the completion of a conversion. This
signal may be used as an interrupt for an external
microcontroller. Bit 31 (EOC) can be captured on the first
rising edge of SCK. Bit 30 is shifted out of the device on the
first falling edge of SCK. The final data bit (Bit 0) is shifted
IN
IN
IN
> V
= 0
< 0
IN
+
IN
REF
/0
V
–
REF
V
REF
, this bit is LOW. If the input is outside the
IN
Bit 31
is >0, this bit is HIGH. If V
EOC
0
0
0
0
IN
> V
REF
Bit 30
DMY
or V
0
0
0
0
IN
< 0, this bit is HIGH.
Bit 29
SIG
1/0
LTC2400
1
1
0
IN
is <0, this
11
Bit 28
EXR
1
0
0
1