x3101 Intersil Corporation, x3101 Datasheet - Page 19

• Manufacturer Part Number: x3101
• Description: 3 Or 4 Cell Li-ion Battery Protection And Monitor Ic
• Manufacturer: Intersil Corporation

Over-Current Protection
In addition to monitoring the battery cell voltages, the
X3100 and X3101 continually monitor the voltage
VCS
tor (R
T
mode (Figure 7). In this mode, the X3100 and X3101
automatically
(UVP/OCP = Vcc) and hence prevent current from
flowing through the terminals P+ and P-.
Figure 5. Over-Current Protection
The 5VDC voltage regulator output (V
active during an over-current protection mode.
Once the device enters over-current protection mode,
the X3100 and X3101 begin a load monitor state. In
the load monitor state, a small current (I
typ.) is passed out of pin OVP/LMON in order to deter-
mine the load resistance. The load resistance is the
impedance seen looking out of pin OVP/LMON,
between terminal P+ and pin VSS (See Figure 5.)
OC
, then the device enters over-current protection
21
X3100/X3101
VSS
SENSE
(VCS
). If VCS
2
OVP/LMON
VCS1
- VCS
R
switch
SENSE
Q2
1
FET Control
) across the current sense resis-
21
Circuitry
VCS2
the
> V
19
OC
discharge
Q10
for a time exceeding
D1
I
LMON
V
RGO
RGO
LMON
R
(Load)
FET
OCR
) is always
= 7.5µA
P-
P+
X3100, X3101
OFF
If the load resistance > R
exceeding T
from over-current protection mode. The discharge FET
is then automatically switched ON (UVP/OCP = Vss)
by the X3100 or X3101, unless the status of UVP/OCP
has been changed in control register (by manipulating
bit UVPC) during the over-current protection mode.
T
nected between pin OCT and VSS. A list of typical
delay times is shown in Table 23. Note that the value
C
The delay T
capacitance C
ing equations:
Table 23. Typical Over-Current Delay Times
The value of V
shown in 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 over-
charge condition or by direct command from the micro-
controller, the cells are not in an undervoltage
condition and the pack has a load, then excessive cur-
rent may flow through Q10 and diode D1. To eliminate
this effect, the gate of Q10 can be turned off by the
microcontroller through an unused X3101 cell balance
output, or directly from a microcontroller port instead of
connecting to V
Symbol
OC
OC
T
T
OCR
/T
OC
should be larger than 1nF.
OCR
are varied using a capacitor (C
Over-current
detection delay
Over-current
release time
T
OC
OCR
T
OCR
Description
OC
OC
RGO
and T
OC
, then the X3100 or X3101 is released
(ms) ≈ 10,000 x C
(ms) ≈ 10,000 x C
can be approximated by the follow-
.
can be selected from the values
OCR
OCR
that results from a particular
(I
0.001
0.001
LMON
C
OC
OC
OC
µ F
µ F
= 0µA) for a time
(µF)
(µF)
10ms (Typ)
10ms (Typ)
January 3, 2008
Delay
OC
) con-
FN8110.1