A/D Converters. ADC12138 Datasheet

ADC12138 Converters. Datasheet pdf. Equivalent

ADC12138 Datasheet
Recommendation ADC12138 Datasheet
Part ADC12138
Description Self-Calibrating 12-Bit Plus Sign Serial I/O A/D Converters
Feature ADC12138; ADC12130/ADC12132/ADC12138 Self-Calibrating 12-Bit Plus Sign Serial I/O A/D Converters with MUX and .
Manufacture National Semiconductor
Datasheet
Download ADC12138 Datasheet




National Semiconductor ADC12138
March 2000
ADC12130/ADC12132/ADC12138
Self-Calibrating 12-Bit Plus Sign Serial I/O A/D
Converters with MUX and Sample/Hold
General Description
The ADC12130, ADC12132 and ADC12138 are 12-bit plus
sign successive approximation A/D converters with serial I/O
and configurable input multiplexer. The ADC12132 and
ADC12138 have a 2 and an 8 channel multiplexer, respec-
tively. The differential multiplexer outputs and A/D inputs are
available on the MUXOUT1, MUXOUT2, A/DIN1 and A/DIN2
pins. The ADC12130 has a two channel multiplexer with the
multiplexer outputs and A/D inputs internally connected. The
ADC12130 family is tested with a 5 MHz clock. On request,
these A/Ds go through a self calibration process that adjusts
linearity, zero and full-scale errors to typically less than ±1
LSB each.
The analog inputs can be configured to operate in various
combinations of single-ended, differential, or
pseudo-differential modes. A fully differential unipolar analog
input range (0V to +5V) can be accommodated with a single
+5V supply. In the differential modes, valid outputs are ob-
tained even when the negative inputs are greater than the
positive because of the 12-bit plus sign output data format.
The serial I/O is configured to comply with the NSC MI-
CROWIRE. For voltage references, see the LM4040 or
LM4041.
Features
n Serial I/O (MICROWIRE, SPI and QSPI Compatible)
n 2 or 8 channel differential or single-ended multiplexer
n Analog input sample/hold function
n Power down mode
n Programmable acquisition time
n Variable digital output word length and format
n No zero or full scale adjustment required
n 0V to 5V analog input range with single 5V power
supply
Key Specifications
n Resolution: 12-bit plus sign
n 12-bit plus sign conversion time: 8.8 µs (max)
n 12-bit plus sign throughput time: 14 µs (max)
n Integral linearity error: ±2 LSB (max)
n Single supply: 3.3V or 5V ±10%
n Power consumption
— 3.3V
15 mW (max)
— 3.3V power down
40 µW (typ)
— 5V
33 mW (max)
— 5V power down
100 µW (typ)
Applications
n Pen-based computers
n Digitizers
n Global positioning systems
ADC12138 Simplified Block Diagram
TRI-STATE® is a registered trademark of National Semiconductor Corporation.
COPSmicrocontrollers, HPCand MICROWIREare trademarks of National Semiconductor Corporation.
© 2000 National Semiconductor Corporation DS012079
DS012079-1
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National Semiconductor ADC12138
Ordering Information
Industrial Temperature Range
−40˚C TA +85˚C
ADC12130CIN
ADC12130CIWM
ADC12132CIMSA
ADC12138CIN
ADC12138CIWM
ADC12138CIMSA
Connection Diagrams
16-Pin Dual-In-Line and
Wide Body SO Packages
NS Package Number
N16E, Dual-In-Line
M16B, Wide Body SO
MSA20, SSOP
N28B, Dual-In-Line
M28B
MSA28, SSOP
20-Pin SSOP Package
Top View
DS012079-2
28-Pin Dual-In-Line, SSOP and
Wide Body SO Packages
Top View
DS012079-47
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Top View
DS012079-3
2



National Semiconductor ADC12138
Pin Descriptions
CCLK
SCLK
DI
DO
EOC
CS
The clock applied to this input controls the su-
cessive approximation conversion time interval
and the acquisition time. The rise and fall times
of the clock edges should not exceed 1 µs.
This is the serial data clock input. The clock
applied to this input controls the rate at which
the serial data exchange occurs. The rising
edge loads the information on the DI pin into
the multiplexer address and mode select shift
register. This address controls which channel
of the analog input multiplexer (MUX) is se-
lected and the mode of operation for the A/D.
With CS low, the falling edge of SCLK shifts
the data resulting from the previous ADC con-
version out on DO, with the exception of the
first bit of data. When CS is low continuously,
the first bit of the data is clocked out on the ris-
ing edge of EOC (end of conversion). When
CS is toggled, the falling edge of CS always
clocks out the first bit of data. CS should be
brought low when SCLK is low. The rise and
fall times of the clock edges should not exceed
1 µs.
This is the serial data input pin. The data ap-
plied to this pin is shifted by the rising edge of
SCLK into the multiplexer address and mode
select register. Table 2 through Table 4 show
the assignment of the multiplexer address and
the mode select data.
The data output pin. This pin is an active push/
pull output when CS is low. When CS is high,
this output is TRI-STATE. The A/D conversion
result (DB0–DB12) and converter status data
are clocked out by the falling edge of SCLK on
this pin. The word length and format of this re-
sult can vary (see Table 1). The word length
and format are controlled by the data shifted
into the multiplexer address and mode select
register (see Table 4).
This pin is an active push/pull output and indi-
cates the status of the ADC12130/2/8. When
low, it signals that the A/D is busy with a con-
version, auto-calibration, auto-zero or power
down cycle. The rising edge of EOC signals
the end of one of these cycles.
This is the chip select pin. When a logic low is
applied to this pin, the rising edge of SCLK
shifts the data on DI into the address register.
This low also brings DO out of TRI-STATE.
With CS low, the falling edge of SCLK shifts
the data resulting from the previous ADC con-
version out on DO, with the exception of the
first bit of data. When CS is low continuously,
the first bit of the data is clocked out on the ris-
ing edge of EOC (end of conversion). When
CS is toggled, the falling edge of CS always
clocks out the first bit of data. CS should be
brought low when SCLK is low. The falling
edge of CS resets a conversion in progress
and starts the sequence for a new conversion.
When CS is brought back low during a conver-
sion, that conversion is prematurely termi-
nated. The data in the output latches may be
corrupted. Therefore, when CS is brought back
low during a conversion in progress the data
output at that time should be ignored. CS may
also be left continuously low. In this case it is
imperative that the correct number of SCLK
pulses be applied to the ADC in order to re-
main synchronous. After the ADC supply
power is applied it expects to see 13 clock
pulses for each I/O sequence. The number of
clock pulses the ADC expects is the same as
the digital output word length. This word length
can be modified by the data shifted in on the
DO pin. Table 4 details the data required.
DOR
This is the data output ready pin. This pin is an
active push/pull output. It is low when the con-
version result is being shifted out and goes
high to signal that all the data has been shifted
out.
CONV
A logic low is required on this pin to program
any mode or change the ADC’s configuration
as listed in the Mode Programming Table
(Table 4) such as 12-bit conversion, Auto Cal,
Auto Zero etc. When this pin is high the ADC is
placed in the read data only mode. While in the
read data only mode, bringing CS low and
pulsing SCLK will only clock out on DO any
data stored in the ADCs output shift register.
The data on DI will be neglected. A new con-
version will not be started and the ADC will re-
main in the mode and/or configuration previ-
ously programmed. Read data only cannot be
performed while a conversion, Auto-Cal or
Auto-Zero are in progress.
PD This is the power down pin. When PD is high
the A/D is powered down; when PD is low the
A/D is powered up. The A/D takes a maximum
of 700 µs to power up after the command is
given.
CH0–CH7
These are the analog inputs of the MUX. A
channel input is selected by the address infor-
mation at the DI pin, which is loaded on the ris-
ing edge of SCLK into the address register
(see Table 2 and Table 3).
The voltage applied to these inputs should not
exceed VA+ or go below GND. Exceeding this
range on an unselected channel will corrupt
the reading of a selected channel.
COM
This pin is another analog input pin. It is used
as a pseudo ground when the analog multi-
plexer is single-ended.
MUXOUT1, These are the multiplexer output
MUXOUT2 pins.
A/DIN1,
A/DIN2
These are the converter input pins. MUXOUT1
is usually tied to A/DIN1. MUXOUT2 is usually
tied to A/DIN2. If external circuitry is placed be-
tween MUXOUT1 and A/DIN1, or MUXOUT2
and A/DIN2 it may be necessary to protect
these pins. The voltage at these pins should
not exceed VA+ or go below AGND (see Figure
5).
VREF+
This is the positive analog voltage reference
input. In order to maintain accuracy, the volt-
age range of VREF (VREF = VREF+ − VREF−) is
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