ISL6580CR Intersil, ISL6580CR Datasheet - Page 16

• 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

Compensation Methodology
Due to the user interface software interface, it is very easy to
change the frequency compensation and see the resulting
performance on a scope or network analyzer. Transient
response is viewed by applying a transient load and
monitoring the output voltage with a scope. Frequency
response is viewed by placing a small resistor between the
output and the feed back network, applying a small sine
wave at the input to the feed back network and measuring
the amplitude and phase shift of the resulting sine wave on
the output. Sweeping the frequency produces plots similar
to those above.
Frequency Domain
It is recommended to place the first zero (F
resonant frequency of the output inductors and capacitors (F
= 1/(2ð÷LC = 10kHz in this case). Then increase F
F
drops below 0dB while keeping the phase margin above 60
degrees. Phase Margin is the difference between 180
degrees and the phase shift of the loop at the frequency
where the gain drops below 0dB (cross over frequency). If
the loops phase shift reaches 180 degrees and has gain
equal to or greater than 0dB, it acts as positive feed back
and the loop will oscillate. Even if the loops phase shift is
slightly below 180 degrees at the cross over frequency, the
loop will respond to transients with overshoot and ringing.
Loop phase shift between 90 and 120 degrees at the cross
over frequency (Phase margin = 60 to 90 degrees) results in
little or no over shoot and ringing. Large phase margins
(>90 degrees) result in slower transient response.
Time Domain
It is recommended to place the first zero (F
resonant frequency of the output inductors and capacitors (F
= 1/(2ð÷LC = 10kHz in this case). Then increase F
F
ringing. The first microseconds of transient response are
primarily dependant on the ESR and ESL of the output
capacitors. After the affects of ESL and ESR pass the loop
must control the response.
P0
P0
to maximize DC gain and the frequency at which gain
to minimize response time over (under) shoot and
16
Z1
Z1
) at the
) at the
Z2
Z2
and
and
ISL6580
Active Transient Response
What is ATR?
In ordinary operation, the ISL6590 and the ISL6580’s form a
closed-loop system that uses enhanced proportional,
integral, differential (PID) control to converge on a target
output voltage. The control loop monitors the delivered load
current and adjusts the pulse-width modulated impulses
accordingly to satisfy the load line. Fast load current
transitions, however, may produce brief under- or overshoots
in the output voltage. The closed loop may fail to
compensate rapidly for these events for several reasons: 1) it
has limited bandwidth, 2) it has processing delay, 3) the
inductors require time to (dis)charge the output capacitor
bank, and 4) the slew rate of the output current may be
extremely fast.
Active transient response (ATR) is engaged if the output
voltage deviates outside a user-defined voltage window. In
this mode, all ISL6580’s may be switched simultaneously as
an open-loop system.
In ordinary operation, the switching of ISL6580 phases is
distributed uniformly in time. An n-phase system, for
example, has successive phases delayed by tp/n, where tp is
the switching period. ATR mode, in addition to the ordinary
synchronous switching, may switch all phases
asynchronously.
Figure 22 is an illustration of how individual phases operate
either independently or simultaneously. ATR improves
FIGURE 21. TYPICAL RESPONSE TO A LOAD TRANSIENT