ncp1080 ON Semiconductor, ncp1080 Datasheet - Page 11

• Manufacturer Part Number: ncp1080
• Description: Integrated Poe-pd & Dc-dc Converter Controller
• Manufacturer: ON Semiconductor

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