ISL6144_07 Datasheet, PDF (17/29 Pages) Intersil Corporation – High Voltage ORing MOSFET Controller

ISL6144
charge pump circuitry starts functioning as the input voltage
at the V_IN pin reaches a value around 8V. The gate voltage
depends on the load current (as explained in previous
sections), The maximum gate voltage will be clamped to a
maximum of V_GQP when load current becomes too high to
be handled with 20mV across the source-drain terminals.
Overall, it takes less than 1ms to reach the load-dependant
final gate voltage value. Note that the Input voltage cannot
be hot swapped and has to rise slowly. A rise time of at least
one ms is recommended for the voltage at VIN pin.
V_IN = 48V; RESISTIVE LOAD = 4A, C_GSEXT = 33nF
V_IN1,V_G1,I_IN1 and HV_REF(VZ) WAVEFORMS
HV_REF(Vz)
5V/DIV
4A
I_IN1
2A/DIV
V_IN = 12V; RESISTIVE LOAD = 5A, C_GSEXT = 33nF
I_IN1
5A/DIV
V_G1
5V/DIV
V_IN1
5V/DIV
V_OUT
5V/DIV
0A
V_G1
10V/DIV
V_IN1
10V/DIV
WHEN V_IN REACHES ~ 8V AND HVREF REACHES
3V to 4V, GATE CHARGE PUMP ACTION STARTS
V_IN1, V_G1, I_IN1 and V_OUT WAVEFORMS
I_IN1
4A
5A/DIV
0A
V_OUT
20V/DIV
FIGURE 20. FIRST FEED V_IN1 START-UP (12V CASE)
The start-up tests were done with the addition of an external
gate to source capacitor to demonstrate start-up time with a
total equivalent gate-source capacitance around 39nF.
SECOND (CONSECUTIVE) FEED START-UP
In this case, the ISL6144 for the second (consecutive) feed
(U4) already has output bias voltage as the first parallel feed
has been turned on and V_OUT is present on the common
bus. As V_IN2 rises, V_G2 rises with it (V_G2 is GATE2 voltage
with respect to GND). When V_IN2 approaches V_IN1 value,
Gate 2 is turned. Second feed gate turn-on is faster than the
first feed as the HVREF capacitor (C₃) is already
charged.The second or consecutive power supply to be
started can be turned on faster than the first power supply, a
rise time of at least 200µs of the second rail is
recommended.
V_IN = 48V; RESISTIVE LOAD = 4A, C_GS(EXT) = 33nF
V_G1
20V/DIV
V_IN1
20V/DIV
WHEN V_IN REACHES ~ 8V
AND HVREF REACHES 3V TO 4V
GATE CHARGE PUMP ACTION STARTS
FIGURE 19. FIRST FEED V_IN1 START-UP (48V CASE)
I_IN2
2A/DIV
V_OUT
20V/DIV
IN THIS CASE GATE VOLTAGE IS MEASURED
BETWEEN GATE2 AND GND
SECOND GATE TURNS ON ONLY
WHEN V_IN2 REACHES V_IN1
V_G2
20V/DIV
POWER SUPPLY
RELATED DELAY
V_IN2
20V/DIV
FIGURE 21. SECOND (CONSECUTIVE) FEED V_IN2 START-UP
17
FN9131.3
February 15, 2007