Electronic Components Datasheet Search
  English  ▼

X  

Preview PDF HTML

MIC4722 Datasheet(PDF) 14 Page - Micrel Semiconductor

Part # MIC4722
Description  3mm x 3mm 2.7MHz 3A PWM Buck Regulator
PDF  20 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Manufacturer  MICREL [Micrel Semiconductor]
Direct Link  http://www.micrel.com
Logo MICREL - Micrel Semiconductor

MIC4722 Datasheet(HTML) 14 Page - Micrel Semiconductor

Back Button MIC4722 Datasheet HTML 10Page - Micrel Semiconductor MIC4722 Datasheet HTML 11Page - Micrel Semiconductor MIC4722 Datasheet HTML 12Page - Micrel Semiconductor MIC4722 Datasheet HTML 13Page - Micrel Semiconductor MIC4722 Datasheet HTML 14Page - Micrel Semiconductor MIC4722 Datasheet HTML 15Page - Micrel Semiconductor MIC4722 Datasheet HTML 16Page - Micrel Semiconductor MIC4722 Datasheet HTML 17Page - Micrel Semiconductor MIC4722 Datasheet HTML 18Page - Micrel Semiconductor Next Button
Zoom Inzoom in Zoom Outzoom out
 14 / 20 page
background image
Micrel, Inc.
MIC4722
September 2007
14
M9999-090507-B
The following Bode analysis show the small signal loop
stability of the MIC4722, it utilizes type III compensation.
This is a dominant low frequency pole, followed by 2
zeros and finally the double pole of the inductor
capacitor filter, creating a final 20dB/decade roll off.
Bode analysis gives us a few important data points;
speed of response (Gain Bandwidth or GBW) and loop
stability. Loop speed or GBW determines the response
time to a load transient. Faster response times yield
smaller voltage deviations to load steps.
Instability in a control loop occurs when there is gain and
positive feedback. Phase margin is the measure of how
stable the given system is. It is measured by determining
how far the phase is from crossing zero when the gain is
equal to 1 (0dB).
-30
-20
-10
0
10
20
30
40
50
60
FREQUENCY (Hz)
Bode Plot
V
IN
=3.3V, V
OUT
=1.8V, I
OUT
=3A
-105
-70
-35
0
35
70
105
140
175
210
100
1k
10k
100k
1M
L=1µH
C
OUT
= 4.7µF
R1 = 10k
R2 = 12.4k
C
FF
= 82pF
GAIN
PHASE
Typically for 3.3Vin and 1.8Vout at 3A;
•
Phase Margin=47 Degrees
•
GBW=156KHz
Gain will also increase with input voltage. The following
graph shows the increase in GBW for an increase in
supply voltage.
-30
-20
-10
0
10
20
30
40
50
60
FREQUENCY (Hz)
Bode Plot
V
IN
=5V, V
OUT
=1.8V, I
OUT
=3A
-105
-70
-35
0
35
70
105
140
175
210
100
1k
10k
100k
1M
L=1µH
C
OUT
= 4.7µF
R1 = 10k
R2 = 12.4k
C
FF
= 82pF
GAIN
PHASE
5Vin, 1.8Vout at 3A load;
•
Phase Margin=43.1 Degrees
•
GBW= 218KHz
Being that the MIC4722 is non-synchronous; the
regulator only has the ability to source current. This
means that the regulator has to rely on the load to be
able to sink current. This causes a non-linear response
at light loads. The following plot shows the effects of the
pole created by the nonlinearity of the output drive
during light load (discontinuous) conditions.
-30
-20
-10
0
10
20
30
40
50
60
FREQUENCY (Hz)
Bode Plot
V
IN
=3.3V,V
OUT
=1.8V,I
OUT
=50mA
-105
-70
-35
0
35
70
105
140
175
210
100
1k
10k
100k
1M
L=1µH
C
OUT
= 4.7µF
R1 = 10k
R2 = 12.4k
C
FF
= 82pF
GAIN
PHASE
3.3Vin, 1.8Vout Iout=50mA;
•
Phase Margin=90.5 Degrees
•
GBW= 64.4KHz
Feed Forward Capacitor
The feedback resistors are a gain reduction block in the
overall system response of the regulator. By placing a
capacitor from the output to the feedback pin, high
frequency signal can bypass the resistor divider, causing
a gain increase up to unity gain.
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
FREQUENCY (Hz)
Gain and Phase
vs. Frequency
0
5
10
15
20
25
100
1k
10k
100k
1M
L=1µH
C
OUT
= 4.7µF
R1 = 10k
R2 = 12.4k
C
FF
= 82pF
GAIN
PHASE
The graph above shows the effects on the gain and
phase of the system caused by feedback resistors and a
feedforward capacitor. The maximum amount of phase
boost achievable with a feedforward capacitor is
graphed below.



Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20


Datasheet Download

Go To PDF Page


Link URL



Does ALLDATASHEET help your business so far?  [ DONATE ] 

About Alldatasheet   |   Advertisement   |   Contact us   |   Privacy Policy   |   Link to Datasheet    |   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
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com