Moteur de recherche de fiches techniques de composants électroniques
  French  ▼

Delete All
ON OFF
ALLDATASHEET.FR

X  

Preview PDF Download HTML

ADP3212A Fiches technique(PDF) 30 Page - ON Semiconductor

No de pièce ADP3212A
Description  7-Bit, Programmable, 3-Phase, Mobile CPU Synchronous Buck Controller
Download  35 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  ONSEMI [ON Semiconductor]
Site Internet  http://www.onsemi.com
Logo ONSEMI - ON Semiconductor

ADP3212A Fiches technique(HTML) 30 Page - ON Semiconductor

Back Button ADP3212A Datasheet HTML 26Page - ON Semiconductor ADP3212A Datasheet HTML 27Page - ON Semiconductor ADP3212A Datasheet HTML 28Page - ON Semiconductor ADP3212A Datasheet HTML 29Page - ON Semiconductor ADP3212A Datasheet HTML 30Page - ON Semiconductor ADP3212A Datasheet HTML 31Page - ON Semiconductor ADP3212A Datasheet HTML 32Page - ON Semiconductor ADP3212A Datasheet HTML 33Page - ON Semiconductor ADP3212A Datasheet HTML 34Page - ON Semiconductor Next Button
Zoom Inzoom in Zoom Outzoom out
 30 / 35 page
background image
ADP3212A, NCP3218A
http://onsemi.com
30
The compensation values can be calculated as follows:
CA +
n
RO TA
RE RB
(eq. 31)
RA +
TC
CA
(eq. 32)
CB +
TB
RB
(eq. 33)
CFB +
TD
RA
(eq. 34)
The standard values for these components are subject to
the tuning procedure described in the Tuning Procedure for
12 section.
CIN Selection and Input Current di/dt Reduction
In continuous inductor−current mode, the source current
of the high−side MOSFET is approximately a square wave
with a duty ratio equal to n
× VOUT/VIN and an amplitude
that is one−nth of the maximum output current. To prevent
large voltage transients, use a low ESR input capacitor sized
for the maximum rms current. The maximum rms capacitor
current occurs at the lowest input voltage and is given by:
ICRMS + D IO
1
n
D *
1
(eq. 35)
ICRMS + 0.18 40 A
1
2
0.18 *
1 + 9.6 A
where IO is the output current.
In a typical notebook system, the battery rail decoupling
is achieved by using MLC capacitors or a mixture of MLC
capacitors and bulk capacitors. In this example, the input
capacitor bank is formed by eight pieces of 10
mF, 25 V MLC
capacitors, with a ripple current rating of about 1.5 A each.
RC Snubber
It is important in any buck topology to use a
resistor−capacitor snubber across the low side power
MOSFET. The RC snubber dampens ringing on the switch
node when the high side MOSFET turns on. The switch node
ringing could cause EMI system failures and increased
stress on the power components and controller. The RC
snubber should be placed as close as possible to the low side
MOSFET. Typical values for the resistor range from 1
W to
10
W. Typical values for the capacitor range from 330 pF to
4.7 nF. The exact value of the RC snubber depends on the
PCB layout and MOSFET selection. Some fine tuning must
be done to find the best values. The equation below is used
to find the starting values for the RC subber.
RSnubber +
1
2
p
fRinging COSS
(eq. 36)
CSnubber +
1
p
fRinging RSnubber
(eq. 37)
PSnubber + CSnubber VInput2 fSwitching
(eq. 38)
Where RSnubber is the snubber resistor.
CSnubber is the snubber capacitor.
fRininging is the frequency of the ringing on the switch node
when the high side MOSFET turns on.
COSS is the low side MOSFET output capacitance at VInput.
This is taken from the low side MOSFET data sheet.
Vinput is the input voltage.
fSwitching is the switching frequency.
PSnubber is the power dissipated in RSnubber.
Selecting Thermal Monitor Components
To monitor the temperature of a single−point hot spot, set
RTTSET1 equal to the NTC thermistor’s resistance at the alarm
temperature. For example, if the alarm temperature for VRTT
is 100
°C and a Vishey thermistor (NTHS−0603N011003J)
with a resistance of 100 k
W at 25°C, or 6.8 kW at 100°C, is
used, the user can set RTTSET1 equal to 6.8 kW (the RTH1 at
100
°C).
Figure 33. Single−Point Thermal Monitoring
TTSNS
ADP3212
VCC
R
5 V
VRTT
R
RTH1
CTT
RTTSET1
To monitor the temperature of multiple−point hot spots,
use the configuration shown in Figure 34. If any of the
monitored hot spots reaches the alarm temperature, the
VRTT signal is asserted. The following calculation sets the
alarm temperature:
RTTSET1 +
1 2 )
V
FD
V
REF
1 2 *
V
FD
V
REF
RTH1AlarmTemperature
(eq. 39)
where VFD is the forward drop voltage of the parallel diode.
Because the forward current is very small, the forward
drop voltage is very low, that is, less than 100 mV. Assuming
the same conditions used for the single−point thermal
monitoring example—that is, an alarm temperature of
100
°C and use of an NTHS−0603N011003J Vishay
thermistor—solving Equation 39 gives a RTTSET of 7.37 kW,
and the closest standard resistor is 7.32 k
W (1%).


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 


Fiches technique Télécharger

Go To PDF Page


Lien URL




Politique de confidentialité
ALLDATASHEET.FR
ALLDATASHEET vous a-t-il été utile ?  [ DONATE ] 

À propos de Alldatasheet   |   Publicité   |   Contactez-nous   |   Politique de confidentialité   |   Echange de liens   |   Fabricants
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