isl6590dr Intersil Corporation, isl6590dr Datasheet - Page 17

• Manufacturer Part Number: isl6590dr
• Description: Digital Multi-phase Pwm Controller For Core-voltage Regulation
• Manufacturer: Intersil Corporation

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/(25aLC) = 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
FIGURE 21. FREQUENCY RESPONSE OF THE CLOSED LOOP
P0
FIGURE 20. PID COMPENSATOR FREQUENCY RESPONSE
60
50
40
30
20
10
-100
-120
to maximize DC gain and the frequency at which gain
0
-20
-40
-60
-80
60
40
20
0
1
1
10
10
Frequency (in KHz)
Frequency (in KHz)
100
17
Loop
Phase
100
1000
1000
Compensation
Phase
Z1
) at the
10000
10000
Z2
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
400
350
300
250
200
150
100
50
0
-50
and
ISL6590
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/(25aLC = 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.
User Interface Software
The ISL6590 controller and the ISL6580 intelligent power
stage have programmable values that can be changed using
the User Interface Software. The loop configuration and
system performance is adjusted using the software. The use
of the software allows the engineer to evaluate the system
performance without having to physically change
components on the board. Primarion PowerCode user
interface software (provided by Intersil and our partner
Primarion).
Below are screen shots showing data entry points, pull down
menus, buttons for help and a tutorial. The user interface
software allows the designer to adjust the load line,
frequency response, ATR and protection modes.
P0
FIGURE 22. TYPICAL RESPONSE TO A LOAD TRANSIENT
to minimize response time over (under) shoot and
Z1
) at the
Z2
and