Datenblatt-Suchmaschine für elektronische Bauteile
  German  ▼
ALLDATASHEETDE.COM

X  

LM4961LQ Datenblatt(PDF) 11 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
Teilenummer LM4961LQ
Bauteilbeschribung  Ceramic Speaker Driver
Download  16 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Hersteller  NSC [National Semiconductor (TI)]
Direct Link  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM4961LQ Datenblatt(HTML) 11 Page - National Semiconductor (TI)

Back Button LM4961LQ Datasheet HTML 7Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 8Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 9Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 10Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 11Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 12Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 13Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 14Page - National Semiconductor (TI) LM4961LQ Datasheet HTML 15Page - National Semiconductor (TI) Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 16 page
background image
Application Information (Continued)
DUTY CYCLE
The maximum duty cycle of the boost converter determines
the maximum boost ratio of output-to-input voltage that the
converter can attain in continuous mode of operation. The
duty cycle for a given boost application is defined as:
Duty Cycle = V
OUT +VDIODE -VIN / VOUT +VDIODE -VSW
This applies for continuous mode operation.
INDUCTANCE VALUE
The first question we are usually asked is: “How small can I
make the inductor.” (because they are the largest sized
component and usually the most costly). The answer is not
simple and involves trade-offs in performance. Larger induc-
tors mean less inductor ripple current, which typically means
less output voltage ripple (for a given size of output capaci-
tor). Larger inductors also mean more load power can be
delivered because the energy stored during each switching
cycle is:
E = L/2 X (lp)2
Where “lp” is the peak inductor current. An important point to
observe is that the LM4961 will limit its switch current based
on peak current. This means that since lp(max) is fixed,
increasing L will increase the maximum amount of power
available to the load. Conversely, using too little inductance
may limit the amount of load current which can be drawn
from the output.
Best performance is usually obtained when the converter is
operated in “continuous” mode at the load current range of
interest, typically giving better load regulation and less out-
put ripple. Continuous operation is defined as not allowing
the inductor current to drop to zero during the cycle. It should
be noted that all boost converters shift over to discontinuous
operation as the output load is reduced far enough, but a
larger inductor stays “continuous” over a wider load current
range.
To better understand these trade-offs, a typical application
circuit (5V to 12V boost with a 10µH inductor) will be ana-
lyzed. We will assume:
V
IN =5V, VOUT = 12V, VDIODE = 0.5V, VSW = 0.5V
Since the frequency is 1.6MHz (nominal), the period is ap-
proximately 0.625µs. The duty cycle will be 62.5%, which
means the ON-time of the switch is 0.390µs. It should be
noted that when the switch is ON, the voltage across the
inductor is approximately 4.5V. Using the equation:
V = L (di/dt)
We can then calculate the di/dt rate of the inductor which is
found to be 0.45 A/µs during the ON-time. Using these facts,
we can then show what the inductor current will look like
during operation:
During the 0.390µs ON-time, the inductor current ramps up
0.176A and ramps down an equal amount during the OFF-
time. This is defined as the inductor “ripple current”. It can
also be seen that if the load current drops to about 33mA,
the inductor current will begin touching the zero axis which
means it will be in discontinuous mode. A similar analysis
can be performed on any boost converter, to make sure the
ripple current is reasonable and continuous operation will be
maintained at the typical load current values. Taiyo-Yudens
NR4012 inductor series is recommended.
MAXIMUM SWITCH CURRENT
The maximum FET switch current available before the cur-
rent limiter cuts in is dependent on duty cycle of the appli-
cation. This is illustrated in a graph in the typical perfor-
mance characterization section which shows typical values
of switch current as a function of effective (actual) duty cycle.
CALCULATING OUTPUT CURRENT OF BOOST
CONVERTER (I
AMP)
As shown in Figure 2 which depicts inductor current, the load
current is related to the average inductor current by the
relation:
I
LOAD =IIND(AVG) x (1 - DC)
(7)
Where "DC" is the duty cycle of the application. The switch
current can be found by:
I
SW =IIND(AVG) + 1/2 (I
RIPPLE)
(8)
Inductor ripple current is dependent on inductance, duty
cycle, input voltage and frequency:
I
RIPPLE =DCx(VIN-VSW)/(fxL)
(9)
combining all terms, we can develop an expression which
allows the maximum available load current to be calculated:
I
LOAD(max) = (1–DC)x(ISW(max)–DC(VIN-VSW))/2FL(10)
The equation shown to calculate maximum load current
takes into account the losses in the inductor or turn-OFF
switching losses of the FET and diode.
20094099
FIGURE 3. 10µH Inductor Current
5V - 12V Boost (LM4961X)
www.national.com
11


Ähnliche Teilenummer - LM4961LQ

HerstellerTeilenummerDatenblattBauteilbeschribung
logo
Texas Instruments
LM4961LQ/NOPB TI1-LM4961LQ/NOPB Datasheet
1Mb / 24P
[Old version datasheet]   Ceramic Speaker Driver
LM4961LQBD TI1-LM4961LQBD Datasheet
1Mb / 23P
[Old version datasheet]   Ceramic Speaker Driver
LM4961LQBD TI1-LM4961LQBD Datasheet
1Mb / 24P
[Old version datasheet]   Ceramic Speaker Driver
More results

Ähnliche Beschreibung - LM4961LQ

HerstellerTeilenummerDatenblattBauteilbeschribung
logo
Texas Instruments
LM4961 TI1-LM4961_14 Datasheet
1Mb / 23P
[Old version datasheet]   Ceramic Speaker Driver
LM4962 TI1-LM4962_14 Datasheet
926Kb / 23P
[Old version datasheet]   Ceramic Speaker Driver
logo
National Semiconductor ...
LM4962 NSC-LM4962 Datasheet
1Mb / 22P
   Ceramic Speaker Driver
LM48555 NSC-LM48555 Datasheet
332Kb / 14P
   Ceramic Speaker Driver
logo
Texas Instruments
LM4961 TI1-LM4961 Datasheet
1Mb / 24P
[Old version datasheet]   Ceramic Speaker Driver
LM48556 TI1-LM48556_14 Datasheet
1Mb / 23P
[Old version datasheet]   Fully Differential, Mono, Ceramic Speaker Driver
LM48556 TI1-LM48556 Datasheet
1Mb / 22P
[Old version datasheet]   Fully Differential, Mono, Ceramic Speaker Driver
logo
National Semiconductor ...
LM48556 NSC-LM48556 Datasheet
1Mb / 20P
   Fully Differential, Mono, Ceramic Speaker Driver
logo
Maxim Integrated Produc...
MAX9788 MAXIM-MAX9788_07 Datasheet
299Kb / 16P
   14VP-P,Class G Ceramic Speaker Driver
Rev 1; 11/07
logo
Integrated Silicon Solu...
IS31AP4915-QFLS2-TR ISSI-IS31AP4915-QFLS2-TR Datasheet
322Kb / 10P
   20VP-P CHARGE PUMP CERAMIC SPEAKER DRIVER
More results


Html Pages

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


Datenblatt Download

Go To PDF Page


Link URL




Privatsphäre und Datenschutz
ALLDATASHEETDE.COM
War ALLDATASHEET hilfreich?  [ DONATE ] 

Über Alldatasheet   |   Werbung   |   Kontakt   |   Privatsphäre und Datenschutz   |   Linktausch   |   Hersteller
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