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PDF LTC1594CS Data sheet ( Hoja de datos )
| Número de pieza | LTC1594CS | |
| Descripción | 4- and 8-Channel/ Micropower Sampling 12-Bit Serial I/O A/D Converters | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1594/LTC1598
4- and 8-Channel,
Micropower Sampling
12-Bit Serial I/O A/D Converters
FEATURES
s 12-Bit Resolution
s Auto Shutdown to 1nA
s Low Supply Current: 320µA Typ
s Guaranteed ±3/4LSB Max DNL
s Single Supply 5V Operation
(3V Versions Available: LTC1594L/LTC1598L)
s Multiplexer: 4-Channel MUX (LTC1594)
8-Channel MUX (LTC1598)
s Separate MUX Output and ADC Input Pins
s MUX and ADC May Be Controlled Separately
s Sampling Rate: 16.8ksps
s I/O Compatible with QSPI, SPI and MICROWIRETM, etc.
s Small Package: 16-Pin Narrow SO (LTC1594)
24-Pin SSOP (LTC1598)
U
APPLICATIONS
s Pen Screen Digitizing
s Battery-Operated Systems
s Remote Data Acquisition
s Isolated Data Acquisition
s Battery Monitoring
s Temperature Measurement
DESCRIPTION
The LTC®1594/LTC1598 are micropower, 12-bit sampling
A/D converters that feature 4- and 8-channel multiplexers,
respectively. They typically draw only 320µA of supply
current when converting and automatically power down to
a typical supply current of 1nA between conversions. The
LTC1594 is available in a 16-pin SO package and the
LTC1598 is packaged in a 24-pin SSOP. Both operate on
a 5V supply. The 12-bit, switched-capacitor, successive
approximation ADCs include a sample-and-hold.
On-chip serial ports allow efficient data transfer to a wide
range of microprocessors and microcontrollers over three
or four wires. This, coupled with micropower consump-
tion, makes remote location possible and facilitates trans-
mitting data through isolation barriers.
The circuit can be used in ratiometric applications or with
an external reference. The high impedance analog inputs
and the ability to operate with reduced spans (to 1.5V full
scale) allow direct connection to sensors and transducers
in many applications, eliminating the need for gain stages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
MICROWIRE is a trademark of National Semiconductor Corporation.
TYPICAL APPLICATION
24µW, 4-Channel, 12-Bit ADC Samples at 200Hz and Runs Off a 5V Supply
OPTIONAL
ADC FILTER
1k 1µF
5V
ANALOG
INPUTS
0V TO 5V
RANGE
20 CH0
21 CH1
22 CH2
23 CH3
24 CH4
1 CH5
2 CH6
3 CH7
18
MUXOUT
8-CHANNEL
MUX
8 COM
17
ADCIN
16 15, 19
VREF VCC
12-BIT
+ SAMPLING
ADC
–
CSADC
CSMUX
CLK
DIN
DOUT
1µF
10
6
5, 14
7
11
SERIAL DATA LINK
MICROWIRE AND
SPI COMPATABLE
MPU
GND
4, 9
12
NC
13
NC
1594/98 TA01
Supply Current vs Sample Rate
1000
100
TA = 25°C
VCC = 5V
VREF = 5V
fCLK = 320kHz
10
1
0.1
1 10
SAMPLE FREQUENCY (kHz)
100
1594/98 TA02
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC1594/LTC1598
Change in Offset
vs Reference Voltage
3.0
TA = 25°C
VCC = 5V
2.5 fCLK = 320kHz
fSMPL = 16.8kHz
2.0
1.5
1.0
0.5
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
REFERENCE VOLTAGE (V)
1594/98 G04
Change in Gain
vs Reference Voltage
–10
–9
TA = 25°C
VCC = 5V
–8 fCLK = 320kHz
fSMPL = 16.8kHz
–7
–6
–5
–4
–3
–2
–1
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
REFERENCE VOLTAGE (V)
1594/98 G07
Effective Bits and S/(N + D)
vs Input Frequency
12 74
11 68
10 62
9 56
8 50
7 44
6 38
5
4
3 TA = 25°C
2
1
VCC = 5V
fCLK = 320kHz
fSMPL = 16.8kHz
0
1 10
100
INPUT FREQUENCY (kHz)
1000
1594/98 G10
Change in Offset vs Temperature
0
– 0.5
–1.0
–1.5
– 2.0
– 2.5
VCC = VREF = 5V
fCLK = 320kHz
fSMPL = 16.8kHz
– 3.0
– 55 – 35 – 15 5 25 45
TEMPERATURE (°C)
65 85
1594/98 G05
Peak-to-Peak ADC Noise
vs Reference Voltage
2.0
TA = 25°C
VCC = 5V
fCLK = 320kHz
1.5
1.0
0.5
0
12 3 4 5
REFERENCE VOLTAGE (V)
1594/98 G08
Spurious Free Dynamic Range
vs Frequency
100
90
80
70
60
50
40
30
20 TA = 25°C
10 VCC = VREF = 5V
fSMPL = 16.8kHz
0
1 10
100 1000
INPUT FREQUENCY (kHz)
1594/98 G11
Change in Linearity
vs Reference Voltage
– 0 .50
– 0 .45
– 0 .40
– 0 .35
TA = 25°C
VCC = 5V
fCLK = 320kHz
fSMPL = 16.8kHz
– 0 .30
– 0 .25
– 0 .20
– 0 .15
– 0 .10
– 0 .05
0
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
REFERENCE VOLTAGE (V)
1594/98 G06
Differential Nonlinearity vs Code
1.0
0.8
0.6
0.4
0.2
0.0
– 0.2
– 0.4
– 0.6
– 0.8
– 1. 0
0
2048
CODE
4096
1594/98 G09
S/(N + D) vs Input Level
80
TA = 25°C
70 VCC = VREF = 5V
fIN = 1kHz
60 fSMPL = 16.8kHz
50
40
30
20
10
0
– 40
–30 –20 –10
INPUT LEVEL (dB)
0
1594/98 G12
5
5 Page 
APPLICATIONS INFORMATION
CSMUX = CSADC = CS
CLK
tsuCS
tCYC
LTC1594/LTC1598
DIN
DOUT
CH0 TO
CH7
ADCIN =
MUXOUT
COM = GND
EN D1
D2 D0
Hi-Z
NULL
BIT
tOFF
D0N‘T CARE
DUMMY CONVERSION
tCONV
Figure 2. LTC1594/LTC1598 Operating Sequence Example: All Channels Off
Hi-Z
1594/98 F02
Data Transfer
The CLK synchronizes the data transfer with each bit
being transmitted on the falling CLK edge and captured
on the rising CLK edge in both transmitting and receiving
systems.
The LTC1594/LTC1598 first receive input data and then
transmit back the A/D conversion results (half duplex).
Because of the half duplex operation, DIN and DOUT may
be tied together allowing transmission over just 3 wires:
CS, CLK and DATA (DIN/DOUT).
Data transfer is initiated by a rising chip select (CS)
signal. After CS rises the input data on the DIN pin is
latched into a 4-bit register on the rising edge of the clock.
More than four input bits can be sent to the DIN pin
without problems, but only the last four bits clocked in
before CS falls will be stored into the 4-bit register. This
4-bit input data word will select the channel in the
muliplexer (see Input Data Word and Tables 1 and 2). To
ensure correct operation the CS must be pulled low
before the next rising edge of the clock.
Once the CS is pulled low, all channels are simulta-
neously switched off after a delay of tOFF to ensure a
break-before-make interval, tOPEN. After a delay of tON
(tOFF + tOPEN), the selected channel is switched on,
allowing the ADC in the chip to acquire input signal and
start the conversion (see Figures 1 and 2). After 1 null bit,
the result of the conversion is output on the DOUT line.
The selected channel remains on, until the next falling
edge of CS. At the end of the data exchange CS should be
brought high. This resets the LTC1594/LTC1598 and
initiates the next data exchange.
CS
SHIFT MUX
ADDRESS IN
DIN1
DOUT1
tSMPL + 1 NULL BIT
DIN2
DOUT2
SHIFT A/D CONVERSION
RESULT OUT
1594/98 AI01
Break-Before-Make
The LTC1594/LTC1598 provide a break-before-make
interval from switching off all the channels simulta-
neously to switching on the next selected channel once
CS is pulled low. In other words, once CS is pulled low,
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC1594CS.PDF ] | |
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