ISL6564 Datasheet, PDF (20/27 Pages) Intersil Corporation – Multi-Phase PWM Controller with Linear 6-bit DAC Capable of Precision rDS(ON) or DCR Differential Current Sensing

ISL6564
OUTPUT CURRENT, 50A/DIV
0A
OUTPUT VOLTAGE,
500mV/DIV
In normal operation, DRVEN remains low until ISL6564
begins soft-start ramp and then changes to high (Figure 14).
When an overcurrent event occurs, DRVEN is pulled to low
instantly (less than 20ns) to disable the driver so that both
upper and lower FETs be turned off (Figure 15). During an
overvoltage condition, DRVEN remains high to allow the
driver turn on the lower FETs based on the PWM input to
discharge the energy stored in the output inductor. Once the
Output voltage is reduced to 0.6V, DRVEN is pulled to low as
shown in Figure 16.
DRVEN, 5V/DIV
0V
2ms/DIV
FIGURE 13. OVERCURRENT BEHAVIOR IN HICCUP MODE.
F_SW = 500kHz
At the beginning of overcurrent shutdown, the controller
places all PWM signals in a high-impedance state within
20ns commanding the Intersil MOSFET driver ICs to turn off
both upper and lower MOSFETs. The system remains in this
state a period of 4096 switching cycles. If the controller is still
enabled at the end of this wait period, it will attempt a soft-
start. If the fault remains, the trip-retry cycles will continue
indefinitely (as shown in Figure 13) until either controller is
disabled or the fault is cleared. Note that the energy
delivered during trip-retry cycling is much less than during
full-load operation, so there, there is no thermal hazard
during this kind of operation.
0V
OUTPUT CURRENT, 50A/DIV
0A
OUTPUT VOLTAGE,
500mV/DIV
0V
2ms/DIV
FIGURE 15. DRVEN DURING OVERCURRENT OPERATION
DRVEN, 5V/DIV
DRVEN, 5V/DIV
VOUT, 1V/DIV
EN, 5V/DIV
500µs/DIV
FIGURE 14. DRVEN WAVEFORM AT STARTUP
Driver Enable Output
The ISL6564 has a driver enable output pin DRVEN. The
DRVEN is designed for the application where ISL6564
needs to work with drivers that can not recognize three-state
PWM input.
20
OUTPUT VOLTAGE,
500mV/DIV
2ms/DIV
FIGURE 16. DRVEN DURING OVERCURRENT OPERATION
There’s no need to use DRVEN when ISL6564 is used to
work with Intersil’s drivers such as ISL6612 and ISL6605.
Current Sense Output
The ISL6564 has 2 current sense output pins IDROOP and
IOUT. They are identical. In typical application, IDROOP pin
is connected to FB pin for the application where load line is
required. IOUT pin was designed for load current
measurement. As shown in typical application schematics
FN9156.2
December 27, 2004