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PDF LTC2990 Data sheet ( Hoja de datos )
| Número de pieza | LTC2990 | |
| Descripción | monitor system temperatures voltages and currents | |
| Fabricantes | Linear Technology Corporation | |
| Logotipo |  |
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Features
n Measures Voltage, Current and Temperature
n Measures Two Remote Diode Temperatures
n ±1°C Accuracy, 0.06°C Resolution
n ±2°C Internal Temperature Sensor
n 14-Bit ADC Measures Voltage/Current
n 3V to 5.5V Supply Operating Voltage
n Four Selectable Addresses
n Internal 10ppm/°C Voltage Reference
n 10-Lead MSOP Package
Applications
n Temperature Measurement
n Supply Voltage Monitoring
n Current Measurement
n Remote Data Acquisition
n Environmental Monitoring
LTC2990
I2C Temperature, Voltage
and Current Monitor
Description
The LTC®2990 is used to monitor system temperatures,
voltages and currents. Through the I2C serial interface,
the device can be configured to measure many combi-
nations of internal temperature, remote temperature,
remote voltage, remote current and internal VCC. The
internal 10ppm/°C reference minimizes the number of
supporting components and area required. Selectable
address and configurable functionality give the LTC2990
flexibility to be incorporated in various systems needing
temperature, voltage or current data. The LTC2990 fits
well in systems needing sub-millivolt voltage resolution,
1% current measurement and 1°C temperature accuracy
or any combination of the three.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
Typical Application
Voltage, Current, Temperature Monitor
RSENSE
2.5V
5V ILOAD
VCC V1
SDA
SCL
ADR0
ADR1
LTC2990
GND
V2
V3
V4
TREMOTE
2990 TA01a
TINTERNAL
MEASURES: TWO SUPPLY VOLTAGES,
SUPPLY CURRENT, INTERNAL AND
REMOTE TEMPERATURES
Temperature Total Unadjusted Error
1.0
0.5
TREMOTE
0
–0.5
–1.0
–50 –25 0 25 50 75 100 125
TAMB (°C)
2990 TA01b
2990f
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LTC2990
Typical Performance Characteristics TA = 25°C, VCC = 3.3V unless otherwise noted
Single-Ended Noise
4000 4800 READINGS
3500
3000
2500
2000
1500
1000
500
0
–3
–2 –1 0 1 2
LSBs (305.18µV/LSB)
3
2990 G10
LTC2990 Differential Noise
500
800 READINGS
400
300
200
100
0
–4
–3 –2 –1 0 1
LSBs (19.42µV/LSB)
2
3
2990 G13
TINT Noise
500
1000 READINGS
400
300
200
100
0
–0.75 –0.5 –0.25 0 0.25
(°C)
0.5 0.75
2990 G16
Single-Ended Transfer Function
6
5 VCC = 5V
4
VCC = 3.3V
3
2
1
0
–1
–1 –0 1 2 3 4 5 6
VX (V)
2990 G11
Differential Transfer Function
0.4
0.3
0.2
0.1
0
–0.1
–0.2
–0.3
–0.4
–0.4 –0.3 –0.2 –0.1 0 0.1 0.2 0.3 0.4
V1-V2 (V)
2990 G14
Remote Diode Noise
600
1000 READINGS
500
400
300
200
100
0
–0.75 –0.5 –0.25 0 0.25
(°C)
0.5 0.75
2990 G17
Single-Ended INL
1.0
0.5
VCC = 3.3V
0
VCC = 5V
–0.5
–1.0
012345
VX (V)
2990 G12
Differential INL
2
1
0
–1
–2
–0.4
–0.2 0
VIN (V)
0.2 0.4
2990 G15
POR Thresholds vs Temperature
2.6
2.4
VCC RISING
2.2
2.0
1.8 VCC FALLING
1.6
1.4
1.2
1.0
–50 –25 0
25 50 75
TAMB (°C)
100 125 150
2990 G18
2990f
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LTC2990
Applications Information
Device Configuration
The LTC2990 is configured by writing the control register
through the serial interface. Refer to Table 4 for control
register bit definition. The device is capable of many ap-
plication configurations including voltage, temperature
and current measurements. It is possible to configure the
device for single or repeated acquisitions. For repeated
acquisitions, only the initial trigger is required and new data
is written over the old data. Acquisitions are frozen during
serial read data transfers to prevent the upper and lower
data bytes for a particular measurement from becoming
out of sync. Internally, both the upper and lower bytes
are written at the same instant. Since serial data transfer
timeout is not implemented, failure to terminate a read
operation will yield an indefinitely frozen wait state. The
device can also make single measurements, or with one
trigger, all of the measurements for the configuration. When
the device is configured for multiple measurements, the
order of measurements is fixed. As each new data result
is ready, the MSB of the corresponding data register is
set, and the corresponding status register bit is set. These
bits are cleared when the corresponding data register is
addressed. The configuration register value at power-up
yields the measurement of only the internal temperature
sensor, if triggered. The four input pins V1 through V4 will
be in a high impedance state, until configured otherwise,
and a measurement triggered.
Data Format
The data registers are broken into 8-bit upper and lower
bytes. Voltage and current conversions are 14-bits. The
upper bits in the MSB registers provide status on the
resulting conversions. These status bits are different for
temperature and voltage conversions:
Temperature: Temperature conversions are reported as
Celsius or Kelvin results described in Tables 7 and 8,
each with 0.0625 degree-weighted LSBs. The format is
controlled by the control register, Bit 7. All temperature
formats, TINT , TR1 and TR2 are controlled by this bit. The
Temperature MSB result register most significant bit
(Bit 7) is the DATA_VALID bit, which indicates whether
the current register contents have been accessed since
the result was written to the register. This bit will be set
when new data is written to the register, and cleared when
accessed. Bit 6 of the register is a sensor-shorted alarm.
This bit of the corresponding register will be high if the
remote sensor diode differential voltage is below 0.14 VDC.
The LTC2990 internal bias circuitry maintains this voltage
above this level during normal operating conditions. Bit 5
of the register is a sensor open alarm. This bit of the cor-
responding register will be high if the remote sensor diode
differential voltage is above 1.0VDC. The LTC2990 internal
bias circuitry maintains this voltage below this level during
normal operating conditions. The two sensor alarms are
only valid after a completed conversion indicated by the
data_valid bit being high. Bit 4 through Bit 0 of the MSB
register are the conversion result bits D[12:8], in two’s
compliment format. Note in Kelvin results, the result will
always be positive. The LSB register contains temperature
result bits D[7:0]. To convert the register contents to
temperature, use the following equation:
T = D[12:0]/16.
See Table 9 for conversion value examples.
Voltage/Current: Voltage results are reported in two respec-
tive registers, an MSB and LSB register. The Voltage MSB
result register most significant bit (Bit 7) is the data_valid
bit, which indicates whether the current register contents
have been accessed since the result was written to the
register. This bit will be set when the register contents are
new, and cleared when accessed. Bit 6 of the MSB register
is the sign bit, Bits 5 though 0 represent bits D[13:8] of
the two’s complement conversion result. The LSB register
holds conversion bits D[7:0]. The LSB value is different
for single-ended voltage measurements V1 through V4,
and differential (current measurements) V1 – V2 and V3
– V4. Single-ended voltages are limited to positive values
in the range 0V to 3.5V. Differential voltages can have input
values in the range of –0.300V to 0.300V.
Use the following equations to convert the register values
(see Table 9 for examples):
VSINGLE-ENDED = D[13:0] • 305.18µV
VDIFFERENTIAL = D[13:0] • 19.42µV, if Sign = 0
VDIFFERENTIAL = (D[13:0] +1) • –19.42µV, if Sign = 1
Current = D[13:0] • 19.42µV/RSENSE, if Sign = 0
Current = (D[13:0] +1) • –19.42µV/RSENSE, if Sign = 1,
2990f
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| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC2990.PDF ] | |
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