MIC2310_08 Datasheet, PDF (26/34 Pages) Micrel Semiconductor – Single-FET, Constant Power-Limit Hot Swap Controller

Micrel, Inc.
Shorted C_PRIMARY Detector Asserts HW_FLT during
Steady-state
Figure 13 illustrates the behavior of the controller to a
shorted C_PRIMARY capacitor condition after steady-state
operation is achieved via a nominal start-up. If a
C_PRIMARY short occurs during steady-state operation,
the CPRIMARY pin voltage will drop below the V_PRIL
threshold voltage and a shorted C_PRIMARY is detected.
When a C_PRIMARY short is detected, the GATE drive
MIC2310
circuit remains enabled and the DISCH output
remains low such that the external MOSFET remains
ON, however, the HW_FLT digital output is asserted.
To repair the damaged C_PRIMARY capacitor and reset
the HW_FLT digital output, the service processor
instructs the main supply to turn off the V_CC supply
voltage to the controller such that V_REG falls below the
controller’s V_VREG(UVLOL) threshold voltage.
V_CC & V_REG
ENABLE
GATE
V_OUT
I_LOAD
CPRIMARY
PWRGD
VVREG(UVLOH)
VPRIH
tPOR
VGSPGH
VPGH
SHORTED CPRIMARY
VPRIL
VVREG(UVLOL)
VVREG(UVLOH)
VGSPGH
VPGL
CPRIMARY REPAIRED
VPRIH
tPOR
HW_FLT
DISCH
Figure 13. Shorted C_PRIMARY Detector Asserts HW_FLT During Steady-State
July 2008
26
M9999-070108-A