1
LTC1392
Micropower Temperature,
Power Supply and
Differential Voltage Monitor
1
2
3
4
8
7
6
5
V
CC
V
IN
+V
IN
GND
D
IN
D
OUT
CLK
CS
LTC1392
LTC1392 TA01
5V
+
R
SENSE
I
LOAD
1
F
MPU
(e.g., 68HC11)
P1.4
P1.3
P1.2
TEMPERATURE (
C)
40
TEMPERATURE ERROR (
C)
5
4
3
2
1
0
1
2
3
4
5
0
40
60
LTC1392 TA02
20
20
80
100
LTC1392C
GUARANTEED
LIMIT
LTC1392I
GUARANTEED
LIMIT
TYPICAL
D
U
ESCRIPTIO
S
FEATURE
s
Complete Ambient Temperature Sensor Onboard
s
System Power Supply Monitor
s
10-Bit Resolution Rail-to-Rail Common-Mode
Differential Voltage Input
s
Available in 8-Pin SO and PDIP
s
0.2
A Supply Current When Idle
s
700
A Supply Current When Sampling at
Maximum Rate
s
Single Supply Voltage: 4.5V to 6V
s
3-Wire Half-Duplex Serial I/O
s
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.
U
S
A
O
PPLICATI
s
Temperature Measurement
s
Power Supply Measurement
s
Current Measurement
s
Remote Data Acquisition
s
Environment Monitoring
, LTC and LT are registered trademarks of Linear Technology Corporation.
U
A
O
PPLICATI
TYPICAL
Complete Temperature, Supply Voltage and
Supply Current Monitor
Output Temperature Error
2
LTC1392
A
U
G
W
A
W
U
W
A
R
BSOLUTE
XI
TI
S
W
U
U
PACKAGE/ORDER I FOR ATIO
(Note 1)
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
S8 PART MARKING
1392
1392I
Consult factory for Military grade parts.
(Note 2, 3)
ELECTRICAL C
C
HARA TERISTICS
LTC1392CN8
LTC1392CS8
LTC1392IN8
LTC1392IS8
T
JMAX
= 125
C,
JA
= 100
C/ W (N8)
T
JMAX
= 125
C,
JA
= 130
C/ W (S8)
1
2
3
4
8
7
6
5
TOP VIEW
D
IN
D
OUT
CLK
CS
V
CC
V
IN
+V
IN
GND
S8 PACKAGE
8-LEAD PLASTIC SO
N8 PACKAGE
8-LEAD PDIP
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Supply To Digital Conversion
Resolution
V
CC
= 4.5V to 6V
10
Bit
Total Absolute Error
V
CC
= 4.5V to 6V
q
8
LSB
Differential Voltage to Digital
Conversion (Full-Scale Input = 1V)
Resolution
10
Bit
Integral Linearity Error (Note 5)
q
0.5
1
LSB
Differential Linearity Error
q
0.5
1
LSB
Offset Error
q
4
LSB
Full-Scale Error
q
15
LSB
Differential Voltage to Digital
Conversion (Full-Scale Input = 0.5V)
Resolution
10
Bit
Integral Linearity Error (Note 5)
q
0.5
2
LSB
Differential Linearity Error
q
0.5
1
LSB
Offset Error
q
8
LSB
Full-Scale Error
q
25
LSB
Temperature to Digital Conversion
Accuracy
T
A
= 25
C (Note 7)
2
C
T
A
= T
MAX
or T
MIN
(Note 7)
q
4
C
Nonlinearity
T
MIN
T
A
T
MAX
(Note 4)
1
C
3
LTC1392
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
ON LEAKAGE
On-Channel Leakage Current (Note 6)
q
1
A
I
OFF LEAKAGE
Off-Channel Leakage Current (Note 6)
q
1
A
V
IH
High Level Input Voltage
V
CC
= 5.25V
q
2
V
V
IL
Low Level Input Voltage
V
CC
= 4.75V
q
0.8
V
I
IH
High Level Input Current
V
IN
= V
CC
q
5
A
I
IL
Low Level Input Current
V
IN
= 0V
q
5
A
V
OH
High Level Output Voltage
V
CC
= 4.75V, I
OUT
= 10
A
q
4.5
4.74
V
V
CC
= 4.75V, I
OUT
= 360
A
2.4
4.72
V
V
OL
Low Level Output Voltage
V
CC
= 4.75V, I
OUT
= 1.6mA
q
0.4
V
I
OZ
Hi-Z Output Current
CS = High
q
5
A
I
SOURCE
Output Source Current
V
OUT
= 0V
25
mA
I
SINK
Output Sink Current
V
OUT
= V
CC
45
mA
I
CC
Supply Current
CS = High
q
0.1
5
A
CS = Low, V
CC
= 5V
q
0.7
1
mA
t
SMPL
Analog Input Sample Time
See Figure 1
1.5
CLK Cycles
t
CONV
Conversion Time
See Figure 1
10
CLK Cycles
t
dDO
Delay Time, CLK
to D
OUT
Data Valid
C
LOAD
= 100pF
q
150
300
ns
t
en
Delay Time, CLK
to D
OUT
Data Enabled
C
LOAD
= 100pF
q
60
150
ns
t
dis
Delay Time, CS
to D
OUT
Hi-Z
q
170
450
ns
t
hDO
Time Output Data Remains Valid After CLK
C
LOAD
= 100pF
30
ns
t
f
D
OUT
Fall Time
C
LOAD
= 100pF
q
70
250
ns
t
r
D
OUT
Rise Time
C
LOAD
= 100pF
q
25
100
ns
C
IN
Input Capacitance
Analog Input On-Channel
30
pF
Analog Input Off-Channel
5
pF
Digital Input
5
pF
(Note 2, 3)
ELECTRICAL C
C
HARA TERISTICS
RECO
M
E
N
DED OPERATI
N
G CO
N
DITIO
N
S
U
U
U
U
W
W
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Supply Voltage
4.5
6
V
f
CLK
Clock Frequency
V
CC
= 5V
150
250
350
kHz
t
CYC
Total Cycle Time
f
CLK
= 250kHz
74
s
Temperature Conversion Only
144
s
t
hDI
Hold Time, D
IN
After CLK
V
CC
= 5V
150
ns
t
suCS
Setup Time CS
Before First CLK
(See Figure 1)
V
CC
= 5V
2
s
t
WAKEUP
Wakeup Time CS
Before Start Bit
(See Figure 1)
V
CC
= 5V
10
s
Temperature Conversion Only
80
s
t
suDI
Setup Time, D
IN
Stable Before CLK
V
CC
= 5V
150
ns
t
WHCLK
Clock High Time
V
CC
= 5V
1.6
s
t
WLCLK
Clock Low Time
V
CC
= 5V
2
s
t
WHCS
CS High Time Between Data Transfer Cycles
V
CC
= 5V, f
CLK
= 250kHz
2
s
t
WLCS
CS Low Time During Data Transfer
V
CC
= 5V, f
CLK
= 250kHz
72
s
Temperature Conversion Only
142
s
4
LTC1392
RECO
M
E
N
DED OPERATI
N
G CO
N
DITIO
N
S
U
U
U
U
W
W
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 PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Differential Nonlinearity
Power Supply Voltage Mode
Differential Nonlinearity
Integral Nonlinearity
Power Supply Voltage Mode
CODE
256
1.0
DIFFERENTIAL NONLINEARITY ERROR (LSB)
0.5
0
0.5
1.0
320 384 448 512
1392 G01
576 640 704 768 832
f
CLK
= 250kHz
T
A
= 25
C
CODE
256
1.0
INTEGRAL NONLINEARITY ERROR (LSB)
0.5
0
0.5
1.0
320 384 448 512
1392 G02
576 640 704 768 832
f
CLK
= 250kHz
T
A
= 25
C
CODE
256
128
0
1.0
DIFFERENTIAL NONLINEARITY ERROR (LSB)
0.5
0
0.5
1.0
384 512
1392 G03
640 768 896 1024
Full Scale = 1V
f
CLK
= 250kHz
T
A
= 25
C
V
CC
= 5V
CODE
256
128
0
1.0
INTEGRAL NONLINEARITY ERROR (LSB)
0.5
0
0.5
1.0
384 512
1392 G04
640 768 896 1024
Full Scale = 1V
f
CLK
= 250kHz
T
A
= 25
C
V
CC
= 5V
Integral Nonlinearity
Integral Nonlinearity
Differential Nonlinearity
CODE
256
128
0
1.0
DIFFERENTIAL NONLINEARITY ERROR (LSB)
0.5
0
0.5
1.0
384 512
1392 G05
640 768 896 1024
Full Scale = 0.5V
f
CLK
= 250kHz
T
A
= 25
C
V
CC
= 5V
CODE
256
128
0
1.0
INTEGRAL NONLINEARITY ERROR (LSB)
0.5
0
0.5
1.0
384 512
1392 G06
640 768 896 1024
Full Scale = 0.5V
f
CLK
= 250kHz
T
A
= 25
C
V
CC
= 5V
5
LTC1392
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
INPUT
SHIFT
REGISTER
BANDGAP
CONTROL
AND TIMING
CS
4
LTC1392 BD
SERIAL
PORT
V
REF
= 2.42V
V
REF
= 1V
V
REF
= 0.5V
ANALOG
INPUT
MUX
10-BIT
SAR
10
BITS
C
SAMPLE
V
CC
8
5
GND
TEMPERATURE
SENSOR
V
CC
GND
D
IN
1
V
REF
+V
IN
V
IN
6
7
COMP
10-BIT
CAPACITIVE DAC
+
+
+
D
OUT
2
CLK
3
BLOCK DIAGRA
M
W
PI
N
FU
N
CTIO
N
S
U
U
U
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.
Supply Current vs Sample Rate
TIME (SEC)
0
TEMPERATURE (
C)
5
10
15
20
1392 G07
25
70
65
60
55
50
45
40
35
30
25
20
30
V
CC
= 5V
N8
S8
Thermal Response in Stirred
Oil Bath
SAMPLE FREQUENCY (Hz)
SUPPLY CURRENT (
A)
1000
100
10
1
0.1
0.1
10
100
1k
10k
100k
1392 G09
1
V
CC
= 5V
f
CLK
= 250kHz
T
A
= 25
C
CS LOW BETWEEN SAMPLES
CS HIGH BETWEEN
SAMPLES
TIME (SEC)
0
TEMPERATURE (
C)
50
100
150
200
1392 G08
250
70
65
60
55
50
45
40
35
30
25
20
300
V
CC
= 5V
N8
S8
Thermal Response in Still Air
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