Zakładka z wyszukiwarką danych komponentów
  Polish  ▼
ALLDATASHEET.PL

X  

LM34914 Arkusz danych(PDF) 9 Page - Texas Instruments

Numer części LM34914
Szczegółowy opis  Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit
Download  24 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Producent  TI [Texas Instruments]
Strona internetowa  http://www.ti.com
Logo TI - Texas Instruments

LM34914 Arkusz danych(HTML) 9 Page - Texas Instruments

Back Button LM34914_15 Datasheet HTML 5Page - Texas Instruments LM34914_15 Datasheet HTML 6Page - Texas Instruments LM34914_15 Datasheet HTML 7Page - Texas Instruments LM34914_15 Datasheet HTML 8Page - Texas Instruments LM34914_15 Datasheet HTML 9Page - Texas Instruments LM34914_15 Datasheet HTML 10Page - Texas Instruments LM34914_15 Datasheet HTML 11Page - Texas Instruments LM34914_15 Datasheet HTML 12Page - Texas Instruments LM34914_15 Datasheet HTML 13Page - Texas Instruments Next Button
Zoom Inzoom in Zoom Outzoom out
 9 / 24 page
background image
RON =
VOUT x (VIN - 1.5)
FS x 1.15 x 10
-10
x VIN
- 1.4k
tON =
(VIN - 1.5)
1.15 x 10
-10
x (RON + 1.4k)
+ 50 ns
FS =
VOUT
2 x L1 x 1.5 x 1020
RL x RON
2
DC =
tON
tON + tOFF
VOUT
VIN
= tON x FS =
FS =
VOUT x (VIN ± 1.5)
1.15 x 10
-10 x (R
ON + 1.4k) x VIN
LM34914
www.ti.com
SNVS453B – MAY 2006 – REVISED MARCH 2013
When in regulation, the LM34914 operates in continuous conduction mode at heavy load currents and
discontinuous conduction mode at light load currents. In continuous conduction mode the inductor’s current is
always greater than zero, and the operating frequency remains relatively constant with load and line variations.
The minimum load current for continuous conduction mode is one-half the inductor’s ripple current amplitude.
The approximate operating frequency is calculated as follows:
(1)
The buck switch duty cycle is equal to:
(2)
In discontinuous conduction mode, where the inductor’s current reaches zero during the off-time forcing a longer-
than-normal off-time, the operating frequency is lower than in continuous conduction mode, and varies with load
current. Conversion efficiency is maintained at light loads since the switching losses decrease with the reduction
in load and frequency. The approximate discontinuous operating frequency can be calculated as follows:
(3)
where RL = the load resistance, and L1 is the circuit’s inductor.
The output voltage is set by the two feedback resistors (R1, R2 in the Block Diagram). The regulated output
voltage is calculated as follows:
VOUT = 2.5 x (R1 + R2) / R2
(4)
Output voltage regulation is based on supplying ripple voltage to the feedback input (FB pin), normally obtained
from the output voltage ripple through the feedback resistors. The LM34914 requires a minimum of 25 mVp-p of
ripple voltage at the FB pin, requiring the ripple voltage at VOUT be higher by the gain factor of the feedback
resistor ratio. The output ripple voltage is created by the inductor’s ripple current passing through R3 which is in
series with the output capacitor. For applications where reduced ripple is required at VOUT, see Applications
Information.
If the voltage at FB rises above 2.9V, due to a transient at VOUT or excessive inductor current which creates
higher than normal ripple at VOUT, the internal over-voltage comparator immediately shuts off the internal buck
switch. The next on-time starts when the voltage FB falls below 2.5V and the inductor current falls below the
current limit threshold.
ON-Time Timer
The on-time for the LM34914 is determined by the RON resistor and the input voltage (VIN), calculated from:
(5)
The inverse relationship with VIN results in a nearly constant frequency as VIN is varied. To set a specific
continuous conduction mode switching frequency (FS), the RON resistor is determined from the following:
(6)
Equation 1, Equation 5, and Equation 6 are valid only during normal operation - i.e., the circuit is not in current
limit. When the LM34914 operates in current limit, the on-time is reduced by approximately 50%. This feature
reduces the peak inductor current which may be excessively high if the load current and the input voltage are
simultaneously high. This feature operates on a cycle-by-cycle basis until the load current is reduced and the
output voltage resumes its normal regulated value.
Copyright © 2006–2013, Texas Instruments Incorporated
Submit Documentation Feedback
9
Product Folder Links: LM34914


Podobny numer części - LM34914_15

ProducentNumer częściArkusz danychSzczegółowy opis
logo
Texas Instruments
LM34914 TI1-LM34914_14 Datasheet
838Kb / 21P
[Old version datasheet]   Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit
More results

Podobny opis - LM34914_15

ProducentNumer częściArkusz danychSzczegółowy opis
logo
National Semiconductor ...
LM34914 NSC-LM34914 Datasheet
328Kb / 14P
   Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit
logo
Texas Instruments
LM34914 TI1-LM34914_14 Datasheet
838Kb / 21P
[Old version datasheet]   Ultra Small 1.25A Step-Down Switching Regulator with Intelligent Current Limit
logo
National Semiconductor ...
LM34917A NSC-LM34917A Datasheet
554Kb / 16P
   Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
logo
Texas Instruments
LM34917A TI-LM34917A_15 Datasheet
967Kb / 22P
[Old version datasheet]   Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
LM34917A TI1-LM34917A_14 Datasheet
919Kb / 21P
[Old version datasheet]   Ultra Small 33V, 1.25A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
logo
Linear Technology
LT3663 LINER-LT3663_15 Datasheet
352Kb / 16P
   1.2A Step-Down Switching Regulator with Output Current Limit
logo
National Semiconductor ...
LM34930 NSC-LM34930 Datasheet
371Kb / 18P
   Ultra Small 33V, 1A Constant On-Time Buck Switching Regulator with Intelligent Current Limit
logo
Monolithic Power System...
MP28127 MPS-MP28127 Datasheet
420Kb / 9P
   1.25A, 5.5V Synchronous Step-Down Switching Regulator
logo
Texas Instruments
LM34910C TI-LM34910C_15 Datasheet
848Kb / 19P
[Old version datasheet]   High Voltage (50V, 1.25A) Step Down Switching Regulator
logo
National Semiconductor ...
LM34910C NSC-LM34910C Datasheet
270Kb / 12P
   High Voltage (50V, 1.25A) Step Down Switching Regulator
More results


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


Arkusz danych Pobierz

Go To PDF Page


Link URL




Polityka prywatności
ALLDATASHEET.PL
Czy Alldatasheet okazała się pomocna?  [ DONATE ] 

O Alldatasheet   |   Reklama   |   Kontakt   |   Polityka prywatności   |   Linki   |   Lista producentów
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