X3102 Datasheet, PDF (24/32 Pages) Intersil Corporation – 3 Cell Li-Ion Battery Protection and Monitor IC

Normal Operation Mode
B+
P+
X3102
Overcurrent Protection Mode
P+ = (RLOAD+RSENSE) x ILMON
Normal Operation Mode
V_OC
VCS₂
UVP/OCP
T_OC
T_OCR
Voc
V_SS
V_CC
V_SS
Event
0
1
2
3
4
FIGURE 14. OVERCURRENT PROTECTION MODE - EVENT DIAGRAM
TABLE 24. OVERCURRENT PROTECTION MODE-EVENT DIAGRAM DESCRIPTION
EVENT
EVENT DESCRIPTION
[0,1)
• Discharge FET is ON (OCP = Vss). Battery cells are permitted to discharge.
• VCS₂₁ (VCS₂–VCS₁) is less than the overcurrent threshold voltage (V_OC).
• The device is in normal operation mode (i.e. not in a protection mode).
[1] • Excessive current flows through the battery terminals P+, dropping the voltage. (See Figure 14.).
• The positive battery terminal voltage (P+) falls, and VCS₂₁ exceeds V_OC.
• The internal overcurrent detection delay timer begins counting down.
• The device is still in Normal Operation Mode
(1,2)
[2]
The internal Overcurrent detection delay timer continues counting for T_OC seconds.
• The internal overcurrent detection delay timer times out, AND VCS₂₁ is still above V_OC.
• The internal overcurrent sense circuitry switches the discharge FET OFF (UVP/OCP = Vcc).
• The device now begins a load monitor state by passing a small test current (I_LMON = 7.5µA) out of pin OVP/LMON. This senses if
an overcurrent condition (i.e. if the load resistance < R_OCR) still exists across P+/P-.
• The device has now entered overcurrent protection mode.
• It is possible to change the status of UVPC and OVPC in the control register, although the status of pins UVP/OCP and OVP/LMON
will not change until the device has returned from overcurrent protection mode.
(2,3) • The X3102 now continuously monitors the load resistance to detect whether or not an overcurrent condition is still present across
the battery terminals P+/P-.
[3] • The device detects the load resistance has risen above R_OCR.
• Voltages P+ and VCS₂₁ return to their normal levels.
• The test current from pin OVP/LMON is stopped (I_LMON = 0µA)
• The device has now returned from the load monitor state
• The internal overcurrent release time timer begins counting down.
• Device is still in overcurrent protection mode.
(3,4)
[4]
The internal overcurrent release timer continues counting for T_OCR seconds.
• The internal overcurrent release timer times out, and VCS₂₁ is still below V_OC.
• The device returns from overcurrent protection mode, and is now in normal operation mode.
• The discharge FET is automatically switched ON (UVP/OCP = Vss) - unless the status of UVPC has been changed in the control
register during the overcurrent protection mode.
• The status of the charge FET remains unaffected.
• Discharge of the battery cells is once again possible.
24
FN8246.0
December 22, 2004