Table of Contents
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FeaTures
Measures Accumulated Battery Charge
n
and Discharge
3.6V to 60V Operating Range for Multiple Cells
n
14-Bit ADC Measures Voltage, Current
n
and Temperature
1% Voltage, Current and Charge Accuracy
n
±50mV Sense Voltage Range
n
High Side Sense
n
2
I
C Interface/SMBus Interface
n
General Purpose Measurements for Any Battery
n
Chemistry and Capacity
Configurable Alert Output/Charge Complete Input
n
Quiescent Current Less Than 150µA
n
Small 8-Lead 3mm × 3mm DFN Package
n
applicaTions
Electric and Hybrid Electric Vehicles
n
Power Tools
n
Electric Bicycles, Motorcycles, Scooters
n
High Power Portable Equipment
n
Photo Voltaics
n
Backup Battery Systems
n
Typical applicaTion
3.3V
2k
2k
2k
V
DD
µP
CHARGER
1µF
LTC2944
+
SENSE
ALCC
R
SENSE
50m
SDA
–
SENSE
SCL
+
GND
MULTICELL
Li-ION
2944 TA01a
For more information
60V Battery Gas Gauge
with Temperature, Voltage
and Current Measurement
DescripTion
The
LTC
2944
measures battery charge state, battery volt-
®
age, battery current and its own temperature in portable
product applications. The wide input voltage range allows
use with multicell batteries up to 60V. A precision coulomb
counter integrates current through a sense resistor between
the battery's positive terminal and the load or charger.
Voltage, current and temperature are measured with an
internal 14-bit No Latency ΔΣ™ ADC. The measurements
are stored in internal registers accessible via the onboard
2
I
C/SMBus Interface.
The LTC2944 features programmable high and low thresh-
olds for all four measured quantities. If a programmed
threshold is exceeded, the device communicates an alert
using either the SMBus alert protocol or by setting a flag
in the internal status register. The LTC2944 requires only
a single low value sense resistor to set the measured
current range.
All registered trademarks and trademarks are the property of their respective owners.
1A
3
LOAD
V
2
1
0
–1
–2
–3
0.1
www.linear.com/LTC2944
LTC2944
Total Charge Error vs
Differential Sense Voltage
+
= 3.6V TO 60V
SENSE
1
10
V
(mV)
SENSE
2944 TA01b
100
2944fa
1
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Related Manuals for Linear Technology LTC2944
Summary of Contents for Linear Technology LTC2944
- Page 1 Small 8-Lead 3mm × 3mm DFN Package using either the SMBus alert protocol or by setting a flag in the internal status register. The LTC2944 requires only applicaTions a single low value sense resistor to set the measured current range.
-
Page 2: Absolute Maximum Ratings
LTC2944 absoluTe MaxiMuM raTings pin conFiguraTion (Notes 1, 2) Supply Voltage (SENSE ) ......–0.3V to 65V TOP VIEW SCL, SDA, ALCC Voltage ......–0.3V to 6V – SENSE ....(–0.3V + V ) to (V + 0.3V) SENSE SENSE –... - Page 3 LTC2944 elecTrical characTerisTics denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. SYMBOL PARAMETER CONDITIONS UNITS Total Charge Error (Note 5) 10mV ≤ |V | ≤ 50mV DC ±1 SENSE 10mV ≤ |V | ≤...
-
Page 4: Timing Diagram
LTC2944 elecTrical characTerisTics denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T = 25°C. SYMBOL PARAMETER CONDITIONS UNITS C Timing Characteristics Maximum SCL Clock Frequency SCL(MAX) Bus Free Time Between Stop/Start µs BUF(MAX) -
Page 5: Typical Performance Characteristics
LTC2944 Typical perForMance characTerisTics Total Charge Error vs Differential Total Charge Error vs Supply Total Charge Error vs Sense Voltage Voltage Temperature 1.00 1.00 = 3.6V TO 60V SENSE 0.75 0.75 0.50 0.50 = 10mV = 10mV SENSE SENSE 0.25 0.25... -
Page 6: Pin Functions
LTC2944 Typical perForMance characTerisTics Temperature Error vs Temperature Voltage Measurements Noise Current Measurements Noise 800 READINGS –1 SENSE + = 3.6V SENSE + = 5.5V –2 SENSE + = 20V SENSE + = 60V –3 –2 –1 –50 –25 –3 –2... -
Page 7: Block Diagram
LTC2944 block DiagraM LTC2944 SUPPLY SENSE ACCUMULATED CHARGE COULOMB COUNTER REGISTER ALCC TEMPERATURE REFERENCE OSCILLATOR SMBUS SENSOR GENERATOR F = 10kHz DATA AND CONTROL – SENSE REGISTERS – 2944 BD 2944fa For more information www.linear.com/LTC2944... -
Page 8: Operation
Overview Voltage, Current and Temperature ADC The LTC2944 is a battery gas gauge designed for use The LTC2944 includes a 14-bit No Latency ΔΣ analog-to- with multicell batteries with terminal voltages from 3.6V digital converter, with internal clock and voltage reference to 60V. -
Page 9: Applications Information
The status of the charge, voltage, current and temperature alerts is reported in the status register shown in Table 2. The LTC2944 register map is shown in Table 1. The Table 2. Status Register (A) LTC2944 integrates current through a sense resistor,... - Page 10 Setting the control bits B[2:1] to [01] configures the ALCC pin as a digital input. In this mode, a low input on the ALCC pin indicates to the LTC2944 that the battery is full and the accumulated charge register is set to its maximum, value FFFFh.
- Page 11 ±50mV. With input signals up to 300mV the SENSE lead to a sense resistor of 500mΩ. This gives a q LTC2944 will remain functional but the precision of the 34μAh and the accumulated charge register can represent coulomb counter is not guaranteed.
- Page 12 B[7:6] to [00] and goes back to sleep. 50mΩ • 0.340mAh The LTC2944 is set to scan mode by setting B[7:6] to M can be set to 1, 4, 16, ... 4096 by programming B[5:3] [10]. In scan mode the ADC converts voltage, current, 2 •...
- Page 13 C. As soon as a measured quantity exceeds the high threshold or Current Registers (O,P), and Current Threshold falls below the low threshold, the LTC2944 sets the cor- Registers (Q,R,S,T) responding flag in the status register and pulls the ALCC pin low if alert mode is enabled via bits B[2:1].
- Page 14 Temperature Registers (U,V) and Temperature of LTC2944. Threshold Registers (W,X) The reduction of the impact of the offset in LTC2944 can As the ADC resolution is 11 bits in temperature mode, the be explained by its integration scheme depicted in Figure 2.
- Page 15 1100100 and the Connected devices can only pull the bus lines low and R/W bit set to zero, as shown in Figure 6. The LTC2944 must never drive the bus high. The bus wires are externally...
- Page 16 C bus arbitration. If the Read Protocol LTC2944 is sending a 1 and reads a 0 on the SDA pin on the rising edge of SCL, it assumes another device with a The master begins a read operation with a START condition...
- Page 17 LTC2944. However, these capacitors Figure 10. LTC2944 Serial Bus SDA Alert Response Protocol can cause problems if the LTC2944 is plugged into a live supply close to its maximum voltage of 65V. The low loss ceramic capacitor, combined with stray inductance...
-
Page 18: Package Description
LTC2944 package DescripTion Please refer to http://www.linear.com/product/LTC2944#packaging for the most recent package drawings. DD Package 8-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1698 Rev C) 0.70 ±0.05 3.5 ±0.05 1.65 ±0.05 2.10 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ±... -
Page 19: Revision History
Updated equation for obtaining temperature (T) 2944fa Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa- For more information www.linear.com/LTC2944 tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. -
Page 20: Typical Application
COMMENTS Battery Gas Gauges LTC2943 C Battery Gas Gauge with Voltage, Current and 3.6V to 20V Operation, 14-Bit Δ∑-ADC, Pin Compatible with LTC2944, Temperature ADC LTC2943-1, 8-Lead (3mm × 3mm) DFN Package LTC2943-1 1A Multicell Battery Gas Gauge with Temperature, 3.6V to 20V Operation, Internal Sense Resistor, 14-Bit Δ∑...
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