công cụ tìm kiếm bảng dữ liệu linh kiện điện tử
  Vietnamese  ▼
ALLDATASHEET.VN

X  

Preview PDF HTML

SP6136 bảng dữ liệu(PDF) 9 Page - Sipex Corporation

tên linh kiện SP6136
Giải thích chi tiết về linh kiện  Synchronous Buck Controller
PDF  18 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
nhà sản xuất  SIPEX [Sipex Corporation]
Trang chủ  http://www.sipex.com
Logo SIPEX - Sipex Corporation

SP6136 bảng dữ liệu(HTML) 9 Page - Sipex Corporation

Back Button SP6136 Datasheet HTML 5Page - Sipex Corporation SP6136 Datasheet HTML 6Page - Sipex Corporation SP6136 Datasheet HTML 7Page - Sipex Corporation SP6136 Datasheet HTML 8Page - Sipex Corporation SP6136 Datasheet HTML 9Page - Sipex Corporation SP6136 Datasheet HTML 10Page - Sipex Corporation SP6136 Datasheet HTML 11Page - Sipex Corporation SP6136 Datasheet HTML 12Page - Sipex Corporation SP6136 Datasheet HTML 13Page - Sipex Corporation Next Button
Zoom Inzoom in Zoom Outzoom out
 9 / 18 page
background image
9
Oct 3-06 Rev L
SP636 Synchronous Buck Controller
© 2006 Sipex Corporation
20VratedMOSFETissufficient.Forconvert-
ers with 0-5Vin, as in the above example,
select a 30V MOSFET.
The calculation of Rds(on) for Top and Bottom
MOSFETs is interrelated and can be done
using the following procedure:
)
Calculate the maximum permissible
power dissipation P(dissipation) based on
required efficiency. The converter in the
above example should deliver an output
power Pout = 3.3V•0A = 33W. For a target
efficiency of 94%, input power Pin is given
by Pin = Pout/0.94 = 35.W. Maximum al-
lowable power dissipation is then:
P(dissipation) = Pin – Pout = 2. W
2)
Calculate the total power dissipation in
top and bottom MOSFETs P(mosFEt) by sub-
tracting inductor losses from P(dissipation)
calculated in step . To simplify, disregard
core losses; then PL = I
2rms • DCR • .4,
where .4 accounts for the increase in DCR
at operating temperature. For the above
example PL = 0.63W. Then:
P(mosFEt) = 2.W – 0.63W = .47W.
3) Calculate Rds(on) of the bottom MOSFET
by allocating 40% of calculated losses to it.
40% dissipation allocation reflects the fact
that the the top MOSFET has essentially no
switching loss. Then P(bottom) = 0.4X.47W
= 0.59W. Rds(on) = P/(I
2rms • .5) where Irms
= Iout •
{-(Vout/Vin)}0.5 and .5 accounts
for the increase in Rds(on) at the operating
temperature. Then:
Rds
(on) =
P
[{I2out • (-Vout/Vin)} • .5]
= 5.4
W.
4)
Allocate 60% of the calculated losses
to the top MOSFET, P(top) = 0.6X.47 =
0.88W. Assume conduction losses equal
to switching losses, then P = 0.5X0.88W =
0.44W. Since it operates at the duty cycle
of D=Vin/Vout
;
then:
Rds(on) =
P
[I
2
out • (Vout/Vin) • .5
]
= 0.7
W.
Gate-to-drain charge Qgd for the top MOS-
FET needs to be specified. A simplified
expression for switching losses is:
Ps = Iout • Vin • f •
{Vin + Iout } ...................(3)
dv/dt
di/dt
where dv/dt and di/dt are the rates at which
voltage and current transition across the top
MOSFET respectively, and
f is the switching
frequency. Voltage switching time(Vin/d
v/dt)
is related to Qgd:
(Vin /d
v/dt) = Qgd/Ig............................... (4)
where Ig is Current charging the gate-to-drain
capacitance. It can be calculated from:
Ig = (VdrivE-VgatE)/RdrivE......................(5)
where VdrivE is the drive voltage of the
SP636 top driver minus the drop across the
boost diode (approximately 4.5V); VgatE is
the top MOSFET’s gate voltage correspond-
ing to Iout (assume 2.5V) and RdrivE is the
internal resistance of the SP636 top driver
(assume 2
Waverageforturn-onandturn-off).
Substituting these values in equation (5) we
get Ig = A. Substituting for Ig
in equation
(4), we get
(Vin /dv/dt) = Qgd. Substituting
for
(Vin /dv/dt) in equation (3) we have:
Ps = Iout • Vin •
f •
{Qgd + (Iout / di/dt)}
Solving for Qgd we get:
Qgd =
{
Ps
_ Iout
} .............. (6)
Iout • Vin •
f
di/dt
Di/dt is usually limited by parasitic DC-Loop
Inductance (Lp) according to di/dt = Vin/Lp.
APPLICATION INFORMATION



Html Pages

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


bảng dữ liệu tải về

Go To PDF Page


Link URL



Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không?  [ DONATE ] 

Alldatasheet là   |   Quảng cáo   |   Liên lạc với chúng tôi   |   Chính sách bảo mật   |   Liên kết đến bảng dữ liệu    |   Trao đổi link   |   Tìm kiếm theo nhà sản xuất
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