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PDF LTC2945 Data sheet ( Hoja de datos )
| Número de pieza | LTC2945 | |
| Descripción | Wide Range I2C Power Monitor | |
| Fabricantes | Linear | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC2945 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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LTC2945
Wide Range
I2C Power Monitor
FEATURES
n Rail-to-Rail Input Range: 0V to 80V
n Wide Input Supply Range: 2.7V to 80V
n Shunt Regulator for Supplies >80V
n Δ∑ ADC with less than ±0.75% Total Unadjusted Error
n 12-Bit Resolution for Current and Voltages
n Internal Multiplier Calculates 24-Bit Power Value
n Stores Minimum and Maximum Values
n Alerts When Limits Exceeded
n Additional ADC Input Monitors an External Voltage
n Continuous Scan and Snapshot Modes
n Shutdown Mode with IQ < 80µA
n Split SDA for Opto-Isolation
n Available in 12-Lead 3mm × 3mm QFN and MSOP
Packages
APPLICATIONS
n Telecom Infrastructure
n Industrial
n Automotive
n Consumer
DESCRIPTION
The LTC®2945 is a rail-to-rail system monitor that mea-
sures current, voltage, and power. It features an operating
range of 2.7V to 80V and includes a shunt regulator for
supplies above 80V to allow flexibility in the selection of
input supply. The current measurement range of 0V to
80V is independent of the input supply. An onboard 0.75%
accurate 12-bit ADC measures load current, input voltage
and an auxiliary external voltage. A 24-bit power value is
generated by digitally multiplying the measured 12-bit load
current and input voltage data. Minimum and maximum
values are stored and an overrange alert with program-
mable thresholds minimizes the need for software polling.
Data is reported via a standard I2C interface. Shutdown
mode reduces power consumption to 20µA.
The LTC2945 I2C interface includes separate data input
and output pins for use with standard or opto-isolated I2C
connections. The LTC2945-1 has an inverted data output
for use with inverting opto-isolator configurations.
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
Wide Range Power Monitor with Onboard ADC and I2C
VIN
4V TO 80V
0.02Ω
TO
LOAD
ADC Differential
Nonlinearity (ADIN)
0.3
0.1µF
NINE I2C
ADDRESSES
SENSE+ SENSE–
VDD ALERT
LTC2945
INTVCC
SCL
ADR1
ADR0
GND
SDAI
SDAO
ADIN
2945 TA01
I2C
INTERFACE
MEASURED
VOLTAGE
0.2
0.1
0.0
–0.1
–0.2
–0.3
0
1024
2048
CODE
3072
4096
2945 TA01a
ADC Integral Nonlinearity
(ADIN)
0.3
0.2
0.1
0.0
–0.1
–0.2
–0.3
0
1024
2048
CODE
3072
4096
2945 TA01b
For more information www.linear.com/LTC2945
2945fb
1
1 page  
LTC2945
E LECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VDD is from 4V to 80V unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN TYP MAX
I2C INTERFACE TIMING
fSCL(MAX)
tLOW
Maximum SCL Clock Frequency
Minimum SCL Low Period
400
0.65 1.3
tHIGH
tBUF(MIN)
Minimum SCL High Period
Minimum Bus Free Time Between Stop/Start
Condition
50 600
0.12 1.3
tHD,STA(MIN)
Minimum Hold Time After (Repeated) Start
Condition
140 600
tSU,STA(MIN)
Minimum Repeated Start Condition Set-Up
Time
30 600
tSU,STO(MIN)
tHD,DATI(MIN)
tHD,DATO(MIN)
tSU,DAT(MIN)
tSP(MAX)
tRST
CX
Minimum Stop Condition Set-Up Time
Minimum Data Hold Time Input
Minimum Data Hold Time Output
Minimum Data Set-Up Time
Maximum Suppressed Spike Pulse Width
Stuck Bus Reset Time
SCL, SDAI Input Capacitance (Note 5)
SCL or SDAI Held Low
30 600
–100 0
300 600 900
30 100
50 110 250
25 33
5 10
UNITS
kHz
µs
ns
µs
ns
ns
ns
ns
ns
ns
ns
ms
pF
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into pins are positive. All voltages are referenced to
ground, unless otherwise noted.
Note 3: An internal shunt regulator limits the INTVCC pin to a minimum of
5.9V. Driving this pin to voltages beyond 5.9V may damage the part. This
pin can be safely tied to higher voltages through a resistor that limits the
current below 35mA.
Note 4: Internal clamps limit the SCL and SDAI pins to a minimum of 5.9V.
Driving these pins to voltages beyond the clamp may damage the part. The
pins can be safely tied to higher voltages through resistors that limit the
current below 5mA.
Note 5: Guaranteed by design and not subject to test.
Note 6:
TUE
=
(ACTUAL
CODE −IDEAL
4096
CODE)
×
100%
where IDEAL CODE is derived from a straight line passing through Code 0
at 0V and Theoretical Code of 4096 at VFS.
Note 7: ∆SENSE is defined as VSENSE+ – VSENSE–
For more information www.linear.com/LTC2945
2945fb
5
5 Page 
LTC2945
OPERATION
The LTC2945 accurately monitors current, voltage, and
power of any supply rail from 0V to 80V. An internal linear
regulator allows the LTC2945 to operate directly from a
4V to 80V rail, or from an external supply voltage between
2.7V and 5.9V. Quiescent current is less than 0.9mA in
normal operation. Enabling shutdown mode via the I2C
interface reduces the quiescent current to below 80μA.
The LTC2945 includes a shunt regulator for operation from
supply voltages above 80V.
The onboard 12-bit analog-to-digital converter (ADC) runs
either continuously or on-demand using snapshot mode.
In the default continuous scan mode, the ADC repeatedly
measures the differential voltage between SENSE+ and
SENSE– (full-scale 102.4mV) the voltage at the SENSE+
or VDD pin (full-scale 102.4V), and the voltage at the ADIN
pin (full-scale 2.048V). The conversion results are stored
in onboard registers.
In snapshot mode, the LTC2945 performs a single mea-
surement of one selected voltage or current. Snapshot
mode is enabled by setting the snapshot mode enable bit
in the CONTROL register via the I2C interface. A status bit
in the CONTROL register monitors the ADC’s conversion;
when complete, the conversion result is stored in the cor-
responding data registers.
Onboard logic tracks the minimum and maximum values
for each ADC measurement, calculates power data by
digitally multiplying the stored current and voltage data,
and triggers a user-configurable alert by pulling the ALERT
pin low when the ADC measured value falls outside the
programmed window thresholds. All logic outputs are
stored in onboard registers. The LTC2945 includes an
I2C interface to access the onboard data registers and to
program the alert threshold and control registers. Two
three-state pins, ADR1 and ADR0, are decoded to allow
nine device addresses (see Table 1). The SDA pin is split
into SDAI (input) and SDAO (output, LTC2945) or SDAO
(output, LTC2945-1) to facilitate opto-isolation.
APPLICATIONS INFORMATION
The LTC2945 offers a compact and complete solution for
high- and low-side power monitoring. With an input com-
mon mode range of 0V to 80V and a wide input supply
operating voltage range from 2.7V to 80V, this device is
ideal for a large variety of power management applications
including automotive, industrial and telecom infrastructure.
The basic application circuit shown in Figure 1 provides
monitoring of high side current with a 0.02Ω resistor
(5.12A full-scale), input voltage (102.4V full-scale) and an
external voltage (2.048V full-scale), all using an internal
12-bit resolution ADC.
VIN
4V TO 80V
C2
0.1µF
RSNS
0.02Ω
SENSE+ SENSE–
VDD SCL
LTC2945
INTVCC
SDAI
ADR1
SDAO
ADR0
ALERT
ADIN
GND
VOUT
3.3V
R1 R2 R3
2k 2k 2k
VDD
SCL
SDA µP
VADIN
INT
GND
2945 F01
Data Converter
Figure 1. Monitoring High Side Current and Voltages
Using the LTC2945
The LTC2945 features an onboard, 12-bit Δ∑ ADC that inher-
ently averages input noise over the measurement window.
The ADC continuously monitors three voltages in sequence:
∆SENSE first, VDD
differential voltage
obreVtwSeENenSES+EsNecSoEn+da,nadndSVENADSIEN–thisirdm.oTnhie-
tored with 25μV resolution (102.4mV full-scale) to allow
accurate measurement across very low value shunt resistors.
The supply voltage at VDD or SENSE+ is directly measured
with 25mV resolution (102.4V full-scale). The voltage at
the uncommitted ADIN pin is measured with 0.5mV resolu-
tion (2.048V full-scale) to allow monitoring of an arbitrary
external voltage. A 12-bit digital word corresponding to
each measured voltage is stored in two adjacent registers
2945fb
For more information www.linear.com/LTC2945
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC2945.PDF ] | |
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