NCP1080
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11
When using the external resistor divider, the NCP1080 has an external reference voltage hysteresis of 15% typical.
Inrush and Operational Current Limitations
The inrush current limit and the operational current limit are programmed individually by an external Rinrush and Rilim1
resistors respectively connected between INRUSH and VPORTN
1,2
, and between ILIM1 and VPORTN
1,2
as shown in
Figure 9.
ILIM1 /
INRUSH
VDDA1
Vbg1
VDDA1
VPORTNx
Ilim_ref
NCP1080
Figure 9. Current Limitation Configuration (Inrush & Ilim1 Pins)
Ilim1
Vds_pgood
threshold
VPORTNx
Pass Switch
Inrush
I_pass_switch
NCP1080
RTN
VDS_PGOOD
0
1
VDDA1
VDDA1
1 V / 9.2 V
2 V
Current_limit_ON
&
detector
Figure 10. Inrush and Ilim1 Selection Mechanism
VDDA1
When VPORT reaches the UVLO_on level, the Cpd
capacitor is charged with the INRUSH current (in order to
limit the internal power dissipation of the passswitch).
Once the Cpd capacitor is fully charged, the current limit
switches from the inrush current to the current limit level
(ilim1) as shown in Figure 10. This transition occurs when
both following conditions are satisfied:
1. The VDS of the passswitch is below the
Vds_pgood low level (1 V typical).
2. The passswitch is no longer in current limit
mode, meaning the gate of the passswitch is
high (above 2 V typical).
The operational current limit will stay selected as long as
Vds_pgood is true (meaning that RTNVPORTN
1,2
is
below the high level of Vds_pgood). This mechanism allows
a current level transition without any current spike in the
passswitch because the operational current limit (ilim1) is
enabled once the passswitch is not limiting the current
anymore, meaning that the Cpd capacitor is fully charged.
Thermal Shutdown
The NCP1080 includes thermal protection which shuts
down the device in case of high power dissipation. Once the
thermal shutdown (TSD) threshold is exceeded, following
blocks are turned off:
" DCDC controller
" Passswitch
" VDDH and VDDL regulators
" CLASS regulator
When the TSD error disappears and if the input line
voltage is still above the UVLO level, the NCP1080
automatically restarts with the current limit set in the inrush
state, the DCDC controller is disabled and the Css