ISL6580CR Intersil, ISL6580CR Datasheet - Page 14

• Manufacturer Part Number: ISL6580CR
• Description: IC DRIVER HIGH SIDE FET 56-QFN
• Manufacturer: Intersil
• Type: High Side/Low Side Driverr

Specifications of ISL6580CR

• Input Type: Non-Inverting
• Number Of Outputs: 12
• On-state Resistance: 20 mOhm
• Current - Output / Channel: 25A
• Current - Peak Output: 35A
• Voltage - Supply: 5 V ~ 12 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 56-VQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Above the resonant frequency of the output LC filter (10kHz
in this case) the gain falls at a rate of 40dB/decade and the
phase shift approaches –180 degrees. At a frequency above
the F = 1/(2ðC*ESR) = 500kHz in this case) the gain slope
changes to –20dB/decade and the phase shift approaches –
90 degrees.
In a closed loop control system, the output is subtracted from
a reference voltage to produce an error voltage. The error
voltage is amplified and fed to the output stage. In a buck
regulator the output stage consists of a Pulse Width
Modulator (PWM), switching transistors (typically
MOSFETs), series inductor(s) and output capacitors. High
gain feedback reduces variation in the output due to
changes in input voltage, load current and component
values. However, high gain at high frequencies can cause
excessive over shoot in response to transients ( if phase shift
> 120 degrees and gain > 0dB ) or oscillation ( if phase shift
> 180 degrees and gain > 0dB ). The trade off in designing
the loop compensation is to achieve fast response to
transients without excessive overshoot or oscillation.
FIGURE 12. TYPICAL ANALOG VOLTAGE LOOP BLOCK
FIGURE 13. DIGITAL CONTROL LOOP BLOCK DIAGRAM
DIAGRAM
14
ISL6580
The ISL6580 subtracts a reference from the output voltage to
produce an error voltage. It converts the error voltage to a 6
bit digital number and sends it to the ISL6590 controller. The
controller processes the error number numerically to provide
gain (Proportional), phase lag (Integration) and phase lead
(Derivative) functions. This forms the digital PID control.
Adjusting The Digital PID
Frequency response of the digital PID compensator is
determined by the Kp, Ki, Kd factors. These factors are
stored in nonvolatile memory and are loaded in the controller
at power on reset. The system designer sets the PID
compensators frequency response using user interface
software. The designer enters the frequencies of the desired
poles and zeros and user interface software calculates the
Kp, Ki and Kd factors. the software will calculate and display
the frequency response of the feedback and the closed loop
system.
FIGURE 14. TYPICAL ANALOG ERROR AMPLIFIER AND
FIGURE 15. DIGITAL PID COMPENSATOR
COMPENSATION