L6924U STMicroelectronics, L6924U Datasheet - Page 26

• Manufacturer Part Number: L6924U
• Description: Battery Management USB Battery Charger System w/integra
• Manufacturer: STMicroelectronics

Specifications of L6924U

• Product: Charge Management
• Battery Type: Li-Ion
• Output Voltage: 4.2 V
• Output Current: 30 mA
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• Package / Case: VFQFPN
• Mounting Style: SMD/SMT
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Application information: monitoring and protection
26/37
Based on
Equation 18
The temperature hysteresis can be estimated by the equation:
Equation 19
Where V
threshold on the falling edge, and NTC
the NTC at temperature (T) expressed in % resistance change per °C. For NTC
the characteristics of the NTC manufacturers (e.g. the 2322615 series by VISHAY). At low
temperature, the hysteresis is approximately:
Equation 20
Obviously at high temperature hysteresis is:
Equation 21
Considering typical values for NTC
Equation 22
And:
Equation 23
If a PTC connected to GND is used, the selection is the same as above, the only difference
is when the battery temperature increases, the voltage on the TH pin increases, and vice
versa. For applications that do not need a monitor of the battery temperature, the NTC can
be replaced with a simple resistor whose value is one half of the pull-up resistor R
In this case, the voltage at the TH pin is always inside the voltage window, and the charge is
always enabled.
TH
Equation 14
is the pin voltage threshold on the rising edge, V
and
T
Equation 17
HYS
T
HYS
Doc ID 14716 Rev 2
T
50
T
HYS
0
°
HYS
C
°
C
T
0°C
=
50
=
0
HYS
°
°
C
C
225
900
225
and NTC
900
T
=
=
R
, it derives that:
R
=
(- %/°C) is the negative temperature coefficient of
mV
900
NTC
225
mV
NTC
900
mV
V
225
mV
V
TH
50
TH
0
mV
−
mV
mV
−
°
×
°
mV
C
×
248
C
−
780
×
. 0
50°C
. 0
V
×
×
=
039
NTC
−
TH
051
−
mV
NTC
NTC
mV
7
780
, the hysteresis is:
248
_
HYS
T
≅
mV
0
50
≅
mV
°
−
2
C
°
2
5 .
C
5 .
TH_HYS
o
o
C
C
is the pin voltage
T
values, see
UP
L6924U
.