X3102 INTERSIL [Intersil Corporation], X3102 Datasheet - Page 23

• Manufacturer Part Number: X3102
• Description: 3 Cell Li-Ion Battery Protection and Monitor IC
• Manufacturer: INTERSIL [Intersil Corporation]

Overcurrent Protection
In addition to monitoring the battery cell voltages, the X3102
continually monitors the voltage VCS
across the current sense resistor (R
for a time exceeding T
protection mode (Figure 7). In this mode, the X3102
automatically switches the discharge FET OFF (UVP/OCP =
Vcc) and hence prevent current from flowing through the
terminals P+ and P-.
The 5VDC voltage regulator output (V
during an overcurrent protection mode.
Once the device enters overcurrent protection mode, the
X3102 begin a load monitor state. In the load monitor state, a
small current (I
LMON in order to determine the load resistance. The load
resistance is the impedance seen looking out of pin OVP/
LMON, between terminal P+ and pin VSS (See Figure 13.)
If the load resistance >
exceeding T
overcurrent protection mode. The discharge FET is then
automatically switched ON (UVP/OCP = Vss) by the X3102,
unless the status of UVP/OCP has been changed in control
register (by manipulating bit UVPC) during the overcurrent
protection mode.
T
between pin OCT and VSS. A list of typical delay times is
shown in Table 23. Note that the value C
than 1nF.
The delay T
capacitance C
equations:
T
OC
OC
/T
(ms) ≈ 10,000 x C
X3102
VSS
OCR
FIGURE 13. OVERCURRENT PROTECTION
are varied using a capacitor (C
OC
OCR
OC
LMON
OVP/LMON
and T
VCS1
, then the X3102 is released from
R
can be approximated by the following
SENSE
= 7.5µA typ.) is passed out of pin OVP/
OCR
OC
Q2
OC
FET Control
R
Circuitry
, then the device enters overcurrent
OCR
VCS2
that results from a particular
(µF)
23
(I
LMON
SENSE
Q10
D1
21
I
RGO
LMON
= 0µA) for a time
V
(VCS
OC
RGO
). If VCS
OC
) is always active
should be larger
2
) connected
–VCS
R
(Load)
OCR
21
1
)
> V
P-
P+
OC
X3102
T
The value of V
Table 6, by setting bits VOC1, VOC0 in the configuration
register using the WCFIG command.
Note: If the Charge FET is turned off, due to an overcharge
condition or by direct command from the microcontroller, the
cells are not in an undervoltage condition and the pack has a
load, then excessive current may flow through Q10 and
diode D1. To eliminate this effect, the gate of Q10 can be
turned off by the microcontroller.
OCR
Symbol
T
T
OCR
OC
TABLE 23. TYPICAL OVERCURRENT DELAY TIMES
(ms) ≈ 10,000 x C
Overcurrent
detection delay
Overcurrent
release time
OC
Description
can be selected from the values shown in
OC
(µF)
0.001
0.001
C
OC
µ
µ
F
F
December 22, 2004
10ms (Typ)
10ms (Typ)
Delay
FN8246.0