LTC1392
Micropower Temperature,
Power Supply and
Differential Voltage Monitor
FEATURES
s
s
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DESCRIPTIO
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Complete Ambient Temperature Sensor Onboard
System Power Supply Monitor
10-Bit Resolution Rail-to-Rail Common-Mode
Differential Voltage Input
Available in 8-Pin SO and PDIP
0.2µA Supply Current When Idle
700µA Supply Current When Sampling at
Maximum Rate
Single Supply Voltage: 4.5V to 6V
3-Wire Half-Duplex Serial I/O
Communicates with Most MPU Serial Ports and All
MPU Parallel I/O Ports
The LTC
®
1392 is a micropower data acquisition system
designed to measure temperature, on-chip supply voltage
and a differential voltage. The differential inputs feature
rail-to-rail common mode input voltage range. The LTC1392
contains a temperature sensor, a 10-bit A/D converter with
sample-and-hold, a high accuracy bandgap reference and
a 3-wire half-duplex serial interface.
The LTC1392 can be programmed to measure ambient
temperature, power supply voltage and an external volt-
age at the differential input pins, that can also be used for
current measurement using an external sense resistor.
When measuring temperature, the output code of the A/D
converter is linearly proportional to the temperature in
°C.
Production trimming achieves
±2°C
initial accuracy at
room temperature and
±4°C
over the full – 40°C to 85°C
temperature range.
The on-chip serial port allows efficient data transfer to a
wide range of MPUs over three or four wires. This,
coupled with low power consumption, makes remote
location sensing possible and facilitates transmitting
data through isolation barriers.
APPLICATI
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Temperature Measurement
Power Supply Measurement
Current Measurement
Remote Data Acquisition
Environment Monitoring
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
Complete Temperature, Supply Voltage and
Supply Current Monitor
1µF
TEMPERATURE ERROR (°C)
Output Temperature Error
5
4
LTC1392C
GUARANTEED
LIMIT
LTC1392I
GUARANTEED
LIMIT
TYPICAL
+
LTC1392
P1.4
MPU
(e.g., 68HC11)
P1.3
P1.2
1
2
3
4
D
IN
D
OUT
CLK
CS
V
CC
–V
IN
+V
IN
GND
8
7
6
5
5V
3
2
1
0
–1
–2
–3
–4
–5
–40 –20
40
20
0
60
TEMPERATURE (°C)
80
100
R
SENSE
I
LOAD
LTC1392 • TA01
U
LTC1392 • TA02
UO
UO
1
LTC1392
ABSOLUTE
(Note 1)
AXI U
RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
D
IN
1
D
OUT
2
CLK 3
CS 4
N8 PACKAGE
8-LEAD PDIP
8
7
6
5
V
CC
–V
IN
+V
IN
GND
Supply Voltage (V
CC
) ................................................ 7V
Input Voltage ................................. – 0.3V to V
CC
+ 0.3V
Output Voltage ............................... – 0.3V to V
CC
+ 0.3V
Operating Temperature Range
LTC1392C............................................... 0°C to 70°C
LTC1392I........................................... – 40°C to 85°C
Junction Temperature.......................................... 125°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec)................. 300°C
ORDER PART
NUMBER
LTC1392CN8
LTC1392CS8
LTC1392IN8
LTC1392IS8
S8 PART MARKING
1392
1392I
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 100°C/ W (N8)
T
JMAX
= 125°C,
θ
JA
= 130°C/ W (S8)
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
PARAMETER
Power Supply To Digital Conversion
Resolution
Total Absolute Error
Differential Voltage to Digital
Conversion (Full-Scale Input = 1V)
Resolution
Integral Linearity Error (Note 5)
Differential Linearity Error
Offset Error
Full-Scale Error
Differential Voltage to Digital
Conversion (Full-Scale Input = 0.5V)
Resolution
Integral Linearity Error (Note 5)
Differential Linearity Error
Offset Error
Full-Scale Error
Temperature to Digital Conversion
Accuracy
Nonlinearity
CONDITIONS
(Note 2, 3)
MIN
TYP
MAX
10
q
UNITS
Bit
LSB
V
CC
= 4.5V to 6V
V
CC
= 4.5V to 6V
±8
10
q
q
q
q
±0.5
±0.5
±1
±1
±4
±15
10
q
q
q
q
±0.5
±0.5
±2
±1
±8
±25
±2
±4
T
A
= 25°C (Note 7)
T
A
= T
MAX
or T
MIN
(Note 7)
T
MIN
≤
T
A
≤
T
MAX
(Note 4)
q
±1
2
U
Bit
LSB
LSB
LSB
LSB
Bit
LSB
LSB
LSB
LSB
°C
°C
°C
W
U
U
W W
W
LTC1392
ELECTRICAL CHARACTERISTICS
SYMBOL
I
ON LEAKAGE
I
OFF LEAKAGE
V
IH
V
IL
I
IH
I
IL
V
OH
V
OL
I
OZ
I
SOURCE
I
SINK
I
CC
t
SMPL
t
CONV
t
dDO
t
en
t
dis
t
hDO
t
f
t
r
C
IN
PARAMETER
On-Channel Leakage Current (Note 6)
Off-Channel Leakage Current (Note 6)
High Level Input Voltage
Low Level Input Voltage
High Level Input Current
Low Level Input Current
High Level Output Voltage
Low Level Output Voltage
Hi-Z Output Current
Output Source Current
Output Sink Current
Supply Current
Analog Input Sample Time
Conversion Time
Delay Time, CLK↓ to D
OUT
Data Valid
Delay Time, CLK↓ to D
OUT
Data Enabled
Delay Time, CS
↑
to D
OUT
Hi-Z
Time Output Data Remains Valid After CLK↓
D
OUT
Fall Time
D
OUT
Rise Time
Input Capacitance
(Note 2, 3)
MIN
q
q
CONDITIONS
TYP
MAX
±1
±1
UNITS
µA
µA
V
V
µA
µA
V
V
V
CC
= 5.25V
V
CC
= 4.75V
V
IN
= V
CC
V
IN
= 0V
V
CC
= 4.75V, I
OUT
= 10µA
V
CC
= 4.75V, I
OUT
= 360µA
V
CC
= 4.75V, I
OUT
= 1.6mA
CS = High
V
OUT
= 0V
V
OUT
= V
CC
CS = High
CS = Low, V
CC
= 5V
See Figure 1
See Figure 1
C
LOAD
= 100pF
C
LOAD
= 100pF
C
LOAD
= 100pF
C
LOAD
= 100pF
C
LOAD
= 100pF
Analog Input On-Channel
Analog Input Off-Channel
Digital Input
q
q
q
q
q
q
q
2
0.8
5
–5
4.5
2.4
4.74
4.72
0.4
±5
– 25
45
V
µA
mA
mA
q
q
0.1
0.7
1.5
10
5
1
µA
mA
CLK Cycles
CLK Cycles
q
q
q
150
60
170
30
70
25
30
5
5
300
150
450
250
100
ns
ns
ns
ns
ns
ns
pF
pF
pF
q
q
RECOM ENDED OPERATING CONDITIONS
SYMBOL
V
CC
f
CLK
t
CYC
t
hDI
t
suCS
t
WAKEUP
t
suDI
t
WHCLK
t
WLCLK
t
WHCS
t
WLCS
PARAMETER
Supply Voltage
Clock Frequency
Total Cycle Time
Hold Time, D
IN
After CLK↑
Setup Time CS↓ Before First CLK↑ (See Figure 1)
Wakeup Time CS↓ Before Start Bit↑ (See Figure 1)
Setup Time, D
IN
Stable Before CLK↑
Clock High Time
Clock Low Time
CS High Time Between Data Transfer Cycles
CS Low Time During Data Transfer
V
CC
= 5V
f
CLK
= 250kHz
Temperature Conversion Only
V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
Temperature Conversion Only
V
CC
= 5V
V
CC
= 5V
V
CC
= 5V
V
CC
= 5V, f
CLK
= 250kHz
V
CC
= 5V, f
CLK
= 250kHz
Temperature Conversion Only
CONDITIONS
MIN
4.5
150
74
144
150
2
10
80
150
1.6
2
2
72
142
250
TYP
MAX
6
350
UNITS
V
kHz
µs
µs
ns
µs
µs
µs
ns
µs
µs
µs
µs
µs
U
U
U
U WW
3
LTC1392
RECOM ENDED OPERATING CONDITIONS
The
q
denotes specifications which apply over the operating temperature
range (0°C
≤
T
A
≤
70°C for commercial grade and – 40°C
≤
T
A
≤
85°C for
industrial grade).
Note 1:
Absolute maximum ratings are those values beyond which the life
of the device may be impaired.
Note 2:
All voltage values are with respect to GND.
Note 3:
Testing done at V
CC
= 5V, CLK = 250kHz and T
A
= 25°C unless
otherwise specified.
Note 4:
Temperature integral nonlinearity is defined as the deviation of the
A/D code versus temperature curve from the best-fit straight line over the
device’s rated temperature range.
Note 5:
Voltage integral nonlinearity is defined as the deviation of a code
from a straight line passing through the actual end points of the transfer
curve.
Note 6:
Channel leakage current is measured after the channel selection.
Note 7:
See guaranteed temperature limit curves vs temperature range on
the first page of this data sheet.
TYPICAL PERFORMANCE CHARACTERISTICS
Differential Nonlinearity
Power Supply Voltage Mode
DIFFERENTIAL NONLINEARITY ERROR (LSB)
Integral Nonlinearity
Power Supply Voltage Mode
INTEGRAL NONLINEARITY ERROR (LSB)
f
CLK
= 250kHz
T
A
= 25°C
0.5
DIFFERENTIAL NONLINEARITY ERROR (LSB)
1.0
f
CLK
= 250kHz
T
A
= 25°C
0.5
1.0
0
0
–0.5
–0.5
–1.0
256 320 384 448 512 576 640 704 768 832
CODE
1392 G01
–1.0
256 320 384 448 512 576 640 704 768 832
CODE
1392 G02
Integral Nonlinearity
DIFFERENTIAL NONLINEARITY ERROR (LSB)
1.0
INTEGRAL NONLINEARITY ERROR (LSB)
1.0
Differential Nonlinearity
1.0
INTEGRAL NONLINEARITY ERROR (LSB)
0.5
Full Scale = 1V
f
CLK
= 250kHz
T
A
= 25°C
V
CC
= 5V
0.5
Full Scale = 0.5V
f
CLK
= 250kHz
T
A
= 25°C
V
CC
= 5V
0
0
–0.5
–0.5
–1.0
0
128 256 384 512 640 768 896 1024
CODE
1392 G04
–1.0
0
128 256 384 512 640 768 896 1024
CODE
1392 G05
4
U
U
U
U W
U WW
Differential Nonlinearity
1.0
Full Scale = 1V
f
CLK
= 250kHz
T
A
= 25°C
V
CC
= 5V
0.5
0
–0.5
–1.0
0
128 256 384 512 640 768 896 1024
CODE
1392 G03
Integral Nonlinearity
Full Scale = 0.5V
f
CLK
= 250kHz
T
A
= 25°C
V
CC
= 5V
0.5
0
–0.5
–1.0
0
128 256 384 512 640 768 896 1024
CODE
1392 G06
LTC1392
TYPICAL PERFORMANCE CHARACTERISTICS
Thermal Response in Stirred
Oil Bath
70
65
60
TEMPERATURE (°C)
V
CC
= 5V
70
65
60
V
CC
= 5V
TEMPERATURE (°C)
55
50
45
40
35
30
25
20
0
5
10
15
20
TIME (SEC)
25
30
1392 G07
55
50
45
40
35
30
25
20
0
50
100
150
200
TIME (SEC)
250
300
S8
N8
SUPPLY CURRENT (µA)
N8
S8
PIN FUNCTIONS
D
IN
(Pin 1):
Digital Input. The A/D configuration word is
shifted into this input.
D
OUT
(Pin 2):
Digital Output. The A/D result is shifted out
of this output.
CLK (Pin 3):
Shift Clock. This clock synchronizes the serial
data.
CS (Pin 4):
Chip Select Input. A logic low on this input
enables the LTC1392.
GND (Pin 5):
Ground Pin. GND should be tied directly to
an analog ground plane.
+V
IN
(Pin 6):
Positive Analog Differential Input. The pin
can be used as a single-ended input by grounding – V
IN
.
– V
IN
(Pin 7):
Negative Analog Differential Input. The input
must be free from noise.
V
CC
(Pin8):
Positive Supply. This supply must be kept free
from noise and ripple by bypassing directly to the ground
plane.
BLOCK DIAGRAM
D
IN
1
TEMPERATURE
SENSOR
GND
V
CC
+V
IN
6
V
REF
–V
IN
7
U W
+
–
+
–
+
–
Thermal Response in Still Air
1000
Supply Current vs Sample Rate
CS LOW BETWEEN SAMPLES
100
CS HIGH BETWEEN
SAMPLES
10
1
V
CC
= 5V
f
CLK
= 250kHz
T
A
= 25°C
0.1
0.1
1
10
100
1k
10k
SAMPLE FREQUENCY (Hz)
100k
1392 G09
1392 G08
W
U
U
U
3
V
REF
= 2.42V
INPUT
SHIFT
REGISTER
BANDGAP
V
REF
= 1V
V
REF
= 0.5V
2
10-BIT
CAPACITIVE DAC
SERIAL
PORT
10
BITS
10-BIT
SAR
CLK
D
OUT
ANALOG
INPUT
MUX
C
SAMPLE
COMP
8
V
CC
5
GND
CONTROL
AND TIMING
4
LTC1392 • BD
CS
5
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