ISL6140 Intersil Corporation, ISL6140 Datasheet - Page 14

• Manufacturer Part Number: ISL6140
• Description: Negative Voltage Hot Plug Controller
• Manufacturer: Intersil Corporation

Inrush Current
In the example in Figure 26, the supply voltage is 48V and
the load resistor (RL) is 620Ω, for around 80mA. The load
capacitance is 100µF (100V). The Sense Resistor (R1) is
0.02Ω (trip point at 2.5A; well above the inrush current here).
Note that the load current starts at 0 (FET off); reaches a
peak of ~850mA as the GATE voltage ramps and turns on
the FET slowly, and then settles out at 80mA, once the CL is
fully charged to the 48V. The width of the inrush current
pulse is 8ms wide. For comparison, with the same
conditions, but without the gate-controlled FET, the current
was over 20A, during a 130µs pulse.
Power Supply Ramp
Figure 27 shows the Power Supply voltage (to the VDD pin,
with respect to GND at the VEE pin) ramping up. In this
case, the values chosen were R4 = 562K; R5 = 5.9K;
R6 = 13.3K; that sets the UV trip point around 38V, and the
OV trip point to 54V. Note that the GATE starts at 0V, and
stays there until the UV trip point (38V) is exceeded; then it
ramps (slowly, based on the external components chosen)
up to around 13V, where it is clamped; it stays there until the
power supply exceeds the OV trip point at 54V (the GATE
shut-off is much faster than the turn-on). The total time scale
is 2 seconds; the VDD ramp speed was simply based on the
inherent characteristic of the particular power supply used.
Load
Current
48V
FIGURE 26. INRUSH CURRENT
PWRGD-bar
14
GATE
ISL6140, ISL6150
Over-Current at 2.3A
In Figure 28, an Electronic Load Generator was used to
ramp the load current; no load resistor or capacitor was
connected. The sense Resistor R1 is 0.02Ω; that should
make the nominal Over-Current trip point 2.5A.
The GATE is high (clamped to around 13V), keeping the
FET on, as the current starts to ramp up from zero; the
GATE starts to go low (to shut off the FET) when the load
current hits 2.3A. Note that it takes only 44µs for the GATE
to shut off the FET (when the load current equals zero).
Keep in mind that the tolerance of the sense resistor (1%
here) and the IC Over-Current trip voltage (V
accuracy of the trip point; that’s why the trip point doesn’t
necessarily equal the 2.5A design target.
Load Current
GATE
FIGURE 28. OVER-CURRENT AT 2.3A
FIGURE 27. POWER SUPPLY RAMP
FIGURE 28. OVER-CURRENT AT 2.3A
2.3 A
CB
R1 = 0.02 oh
48V
No cap
) affect the
Ω