LP3954 Datasheet, PDF (31/60 Pages) National Semiconductor (TI) – Advanced Lighting Management Unit

LP3954
www.ti.com
FF
E0
C0
A0
80
60
40
20
00
0
0.2 0.4 0.6 0.8
1
INPUT VOLTAGE × V_DDA
Figure 33. ADC Code vs Input Voltage in
Temperature Measurement Mode
SNVS340D – JUNE 2005 – REVISED MARCH 2013
100
10
1
0.1
0.01
-40 -20 0 20 40 60 80 100 120
TEMPERATURE (°C)
Figure 34. Example Curve for Thermistor
EXAMPLE TEMP SENSOR READING AT DIFFERENT TEMPERATURES (R(25°C)=1MΩ)
T°C
R(MΩ)
Rt(MΩ)
V(ASE)
-40
1
60
2.7540984
0
1
4
2.24
25
1
1
1.4
60
1
0.2
0.4666667
100
1
0.04
0.1076923
7V Shielding
To shield LP3954 from high input voltages 6…7.2V the use of external 2.8V LDO is required. This 2.8V voltage
protects internally the device against high voltage condition. The recommended connection is as shown in the
picture below. Internally both logic and analog circuitry works at 2.8V supply voltage. Both supply voltage pins
should have separate filtering capacitors.
BATTERY
4.7 PH
LDO
2.8V
C_IN
10 PF
2.8V
C_VDD
100 nF
C_VDDA
1 PF
V_DD1
V_DD2
V_DDA
LDO
Digital
supply
voltage
Analog
supply
voltage
SW
LP3954
In cases where high voltage is not an issue the connection is as shown below.
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