ISL6297CRZ-T Intersil, ISL6297CRZ-T Datasheet - Page 14

• Manufacturer Part Number: ISL6297CRZ-T
• Description: IC CHARGER LI-ION POLYMER 16-QFN
• Manufacturer: Intersil

Specifications of ISL6297CRZ-T

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion), Lithium-Polymer (Li-Pol)
• Voltage - Supply: 4.3 V ~ 6.5 V
• Operating Temperature: -20°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 16-VQFN Exposed Pad, 16-HVQFN, 16-SQFN, 16-DHVQFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: ISL6297CRZ-TTR

The ratio, K, of the TEMP pin voltage to the bias voltage is:
and
At V
Similarly, at V
Using these equations to calculate the ratio of the thermistor
hot to cold resistance results in:
and
where R
resistance values at the cold and hot temperature limits
respectively.
It is usually difficult to find an NTC thermistor that has the
exact ratio given in Equation 12. A thermistor with a ratio
larger than 6.84, that is:
can be used in series with a regular resistor to form an
effective thermistor that has the right ratio, as shown in
Figure 12.
K
R
K
K
R
-----------------------
R
R
-----------------------
R
R
FIGURE 12. EFFECTIVE NTC THERMISTOR CIRCUIT
T
U
TCOLD
TCOLD
THOT
THOT
=
=
=
=
TMIN
=
--------------------- -
R
---------- -
2.88
0.718
-------------- -
2.0
2.88
------------ -
1 K
0.44R
T
R
K
–
+
TCOLD
T
,
≥
=
R
ISL6297
=
6.84
=
U
×
-----------------------
0.332R
TCOLD
0.6844
2.27R
R
0.2493
TMAX
U
and R
·
U
·
U
.
=
THOT
V2P8
TEMP
GND
6.84
are the NTC thermistor
14
R
R
R
T
U
S
(EQ. 10)
(EQ. 11)
(EQ. 12)
(EQ. 13)
(EQ. 14)
(EQ. 8)
(EQ. 9)
ISL6297
With the series resistor R
as:
Once the thermistor and the temperature limits are selected,
R
and
To summarize, the NTC thermistor circuit design requires
three steps:
Example:
The charger is designed to charge the battery with the
temperature range from -5°C to +45°C. The 10kΩ NTC
thermistor NCP15XH103F03RC from Murata
(http://www.murata.com) satisfies Equation 14. The
resistance values for this thermistor are given in Table 3. The
typical resistance at -5°C and +45°C are:
Using Equation 16 and Equation 17 results in:
R
Selecting R
temperature threshold of -5.1°C and a high temperature
threshold of +44.9°C.
R
------------------------------------- -
R
R
TEMP (°C)
1. Find an NTC thermistor that satisfies Equation 14. The
2. Calculate the series resistance according to Equation 16.
3. Calculate the pull-up resistance according to Equation 17.
R
S
S
S
S
U
S
R
R
and R
= 41.6Ω and R
+
temperature limits are determined by the application
requirement.
TABLE 3. RESISTANCE TABLE OF NCP15XH103F03RC
-10
=
=
+
TCOLD
THOT
40
45
50
55
-5
0
6
7
R
R
R
------------------------------------------------------------- -
0.44
TCOLD
THOT
TCOLD
U
= 4.9169kΩ.
×
S
can be calculated using:
= 33.8922kΩ and
(
R
= 41.2Ω and R
R-LOW (kΩ)
=
5.84
S
–
41.4765
33.1462
26.6780
20.7560
19.9227
5.7443
4.8333
4.0833
3.4634
6.84R
+
6.84
R
U
TCOLD
= 14.931kΩ.
THOT
S
)
, Equation 12 can be re-written
R-CENTER (kΩ)
U
= 15kΩ gives a low
42.5062
33.8922
27.2186
21.1230
20.2666
5.8336
4.9169
4.1609
3.5350
R-HIGH (kΩ)
43.5570
34.6515
27.7675
21.4944
20.6143
5.9238
5.0015
4.2395
3.6076
July 30, 2007
(EQ. 15)
(EQ. 16)
(EQ. 17)
FN9215.2