Electronic Components Datasheet Search
  English  ▼

Delete All
ON OFF
ALLDATASHEET.COM

X  

Preview PDF Download HTML

ISL62771 Datasheet(PDF) 26 Page - Renesas Technology Corp

Part No. ISL62771
Description  Multiphase PWM Regulator for AMD Fusion™ Mobile CPUs Using SVI 2.0
Download  35 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  RENESAS [Renesas Technology Corp]
Direct Link  http://www.renesas.com
Logo RENESAS - Renesas Technology Corp

ISL62771 Datasheet(HTML) 26 Page - Renesas Technology Corp

Back Button ISL62771 Datasheet HTML 22Page - Renesas Technology Corp ISL62771 Datasheet HTML 23Page - Renesas Technology Corp ISL62771 Datasheet HTML 24Page - Renesas Technology Corp ISL62771 Datasheet HTML 25Page - Renesas Technology Corp ISL62771 Datasheet HTML 26Page - Renesas Technology Corp ISL62771 Datasheet HTML 27Page - Renesas Technology Corp ISL62771 Datasheet HTML 28Page - Renesas Technology Corp ISL62771 Datasheet HTML 29Page - Renesas Technology Corp ISL62771 Datasheet HTML 30Page - Renesas Technology Corp Next Button
Zoom Inzoom in Zoom Outzoom out
 26 / 35 page
background image
ISL62771
FN8321 Rev 4.00
Page 26 of 35
November 18, 2015
current sensing network parameters to minimize engineering
time.
VCn(s) also needs to represent real-time Io(s) for the controller to
achieve good transient response. Transfer function Acs(s) has a
pole
sns and a zero L. One needs to match L and sns so
Acs(s) is unity gain at all frequencies. By forcing L equal to sns
and solving for the solution, Equation 18 gives Cn value.
For example, given N = 2, Rsum = 3.65kΩ, Rp = 11kΩ,
Rntcs =2.61kΩ, Rntc = 10kΩ, DCR = 0.88mΩ and L = 0.36µH,
Equation 18 gives Cn = 0.294µF.
Assuming the compensator design is correct, Figure 23 shows the
expected load transient response waveforms if Cn is correctly
selected. When the load current Icore has a square change, the
output voltage Vcore also has a square response.
If Cn value is too large or too small, VCn(s) does not accurately
represent real-time Io(s) and worsens the transient response.
Figure 24 shows the load transient response when Cn is too
small. Vcore sags excessively upon load insertion and may create
a system failure. Figure 25 shows the transient response when
Cn is too large. Vcore is sluggish in drooping to its final value.
There is excessive overshoot if load insertion occurs during this
time, which may negatively affect the CPU reliability.
Figure 26 shows the output voltage ringback problem during
load transient response. The load current io has a fast step
change, but the inductor current iL cannot accurately follow.
Instead, iL responds in first-order system fashion due to the
nature of the current loop. The ESR and ESL effect of the output
capacitors makes the output voltage Vo dip quickly upon load
current change. However, the controller regulates Vo according to
the droop current idroop, which is a real-time representation of iL;
therefore, it pulls Vo back to the level dictated by iL, causing the
ringback problem. This phenomenon is not observed when the
output capacitor has very low ESR and ESL, as is the case with all
ceramic capacitors.
Figure 27 shows two optional circuits for reduction of the
ringback. Cn is the capacitor used to match the inductor time
constant. It usually takes the parallel of two (or more) capacitors
to get the desired value. Figure 27 shows that two capacitors
(Cn.1 and Cn.2) are in parallel. Resistor Rn is an optional
component to reduce the Vo ringback. At steady state,
Cn
L
Rntcnet
Rsum
N
---------------
Rntcnet
Rsum
N
---------------
+
------------------------------------------ DCR
---------------------------------------------------------------
=
(EQ. 18)
FIGURE 23. DESIRED LOAD TRANSIENT RESPONSE WAVEFORMS
o
i
Vo
FIGURE 24. LOAD TRANSIENT RESPONSE WHEN Cn IS TOO SMALL
o
i
Vo
FIGURE 25. LOAD TRANSIENT RESPONSE WHEN Cn IS TOO LARGE
o
i
Vo
FIGURE 26. OUTPUT VOLTAGE RINGBACK PROBLEM
o
i
Vo
L
i
RING
BACK
FIGURE 27. OPTIONAL CIRCUITS FOR RINGBACK REDUCTION
Cn.2
Rntcs
Rntc
Rp
Ri
ISUM+
ISUM-
Rip
Cip
OPTIONAL
Vcn
Cn.1
Rn
OPTIONAL
+
-


Html Pages

1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31  32  33  34  35 


Datasheet Download

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEET.COM
Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Datasheet Upload   |   Contact us   |   Privacy Policy   |   Link Exchange   |   Manufacturer List
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn