Moteur de recherche de fiches techniques de composants électroniques
  French  ▼
ALLDATASHEET.FR

X  

LM2830ZSD Fiches technique(PDF) 10 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
No de pièce LM2830ZSD
Description  High Frequency 1.0A Load - Step-Down DC-DC Regulator
Download  24 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricant  NSC [National Semiconductor (TI)]
Site Internet  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM2830ZSD Fiches technique(HTML) 10 Page - National Semiconductor (TI)

Back Button LM2830ZSD Datasheet HTML 6Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 7Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 8Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 9Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 10Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 11Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 12Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 13Page - National Semiconductor (TI) LM2830ZSD Datasheet HTML 14Page - National Semiconductor (TI) Next Button
Zoom Inzoom in Zoom Outzoom out
 10 / 24 page
background image
Applications Information
THEORY OF OPERATION
The LM2830 is a constant frequency PWM buck regulator IC
that delivers a 1.0A load current. The regulator has a preset
switching frequency of 1.6MHz or 3.0MHz. This high fre-
quency allows the LM2830 to operate with small surface
mount capacitors and inductors, resulting in a DC/DC con-
verter that requires a minimum amount of board space. The
LM2830 is internally compensated, so it is simple to use and
requires few external components. The LM2830 uses
current-mode control to regulate the output voltage. The
following operating description of the LM2830 will refer to the
Simplified Block Diagram (Figure 1) and to the waveforms in
Figure 2. The LM2830 supplies a regulated output voltage by
switching the internal PMOS control switch at constant fre-
quency and variable duty cycle. A switching cycle begins at
the falling edge of the reset pulse generated by the internal
oscillator. When this pulse goes low, the output control logic
turns on the internal PMOS control switch. During this on-
time, the SW pin voltage (V
SW) swings up to approximately
V
IN, and the inductor current (IL) increases with a linear
slope. I
L is measured by the current sense amplifier, which
generates an output proportional to the switch current. The
sense signal is summed with the regulator’s corrective ramp
and compared to the error amplifier’s output, which is pro-
portional to the difference between the feedback voltage and
V
REF. When the PWM comparator output goes high, the
output switch turns off until the next switching cycle begins.
During the switch off-time, inductor current discharges
through the Schottky catch diode, which forces the SW pin to
swing below ground by the forward voltage (V
D)ofthe
Schottky catch diode. The regulator loop adjusts the duty
cycle (D) to maintain a constant output voltage.
SOFT-START
This function forces V
OUT to increase at a controlled rate
during start up. During soft-start, the error amplifier’s refer-
ence voltage ramps from 0V to its nominal value of 0.6V in
approximately 600 µs. This forces the regulator output to
ramp up in a controlled fashion, which helps reduce inrush
current.
OUTPUT OVERVOLTAGE PROTECTION
The over-voltage comparator compares the FB pin voltage
to a voltage that is 15% higher than the internal reference
V
REF. Once the FB pin voltage goes 15% above the internal
reference, the internal PMOS control switch is turned off,
which allows the output voltage to decrease toward regula-
tion.
UNDERVOLTAGE LOCKOUT
Under-voltage lockout (UVLO) prevents the LM2830 from
operating until the input voltage exceeds 2.73V (typ). The
UVLO threshold has approximately 430 mV of hysteresis, so
the part will operate until V
IN drops below 2.3V (typ). Hys-
teresis prevents the part from turning off during power up if
V
IN is non-monotonic.
CURRENT LIMIT
The LM2830 uses cycle-by-cycle current limiting to protect
the output switch. During each switching cycle, a current limit
comparator detects if the output switch current exceeds
1.75A (typ), and turns off the switch until the next switching
cycle begins.
THERMAL SHUTDOWN
Thermal shutdown limits total power dissipation by turning
off the output switch when the IC junction temperature ex-
ceeds 165˚C. After thermal shutdown occurs, the output
switch doesn’t turn on until the junction temperature drops to
approximately 150˚C.
Design Guide
INDUCTOR SELECTION
The Duty Cycle (D) can be approximated quickly using the
ratio of output voltage (V
O) to input voltage (VIN):
The catch diode (D1) forward voltage drop and the voltage
drop across the internal PMOS must be included to calculate
a more accurate duty cycle. Calculate D by using the follow-
ing formula:
V
SW can be approximated by:
V
SW =IOUT xRDSON
The diode forward drop (V
D) can range from 0.3V to 0.7V
depending on the quality of the diode. The lower the V
D, the
higher the operating efficiency of the converter. The inductor
value determines the output ripple current. Lower inductor
values decrease the size of the inductor, but increase the
output ripple current. An increase in the inductor value will
decrease the output ripple current.
One must ensure that the minimum current limit (1.2A) is not
exceeded, so the peak current in the inductor must be
calculated. The peak current (I
LPK) in the inductor is calcu-
lated by:
I
LPK =IOUT +
∆i
L
20197466
FIGURE 2. Typical Waveforms
www.national.com
10


Numéro de pièce similaire - LM2830ZSD

FabricantNo de pièceFiches techniqueDescription
logo
Texas Instruments
LM2830ZSD/NOPB TI-LM2830ZSD/NOPB Datasheet
1Mb / 37P
[Old version datasheet]   LM2830/-Q1 High-Frequency 1.0-A Load Step-Down DC-DC Regulator
More results

Description similaire - LM2830ZSD

FabricantNo de pièceFiches techniqueDescription
logo
Texas Instruments
LM2832 TI1-LM2832 Datasheet
1Mb / 34P
[Old version datasheet]   High Frequency 2.0A Load - Step-Down DC-DC Regulator
logo
National Semiconductor ...
LM2832 NSC-LM2832 Datasheet
893Kb / 27P
   High Frequency 2.0A Load - Step-Down DC-DC Regulator
logo
Texas Instruments
LM2831 TI1-LM2831_14 Datasheet
1Mb / 34P
[Old version datasheet]   High Frequency 1.5A Load - Step-Down DC-DC Regulator
LM2832 TI1-LM2832_14 Datasheet
1Mb / 33P
[Old version datasheet]   High Frequency 2.0A Load - Step-Down DC-DC Regulator
logo
National Semiconductor ...
LM2831 NSC-LM2831 Datasheet
890Kb / 27P
   High Frequency 1.5A Load - Step-Down DC-DC Regulator
logo
Texas Instruments
LM2831 TI-LM2831_15 Datasheet
1Mb / 38P
[Old version datasheet]   LM2831 High-Frequency 1.5-A Load ??Step-Down DC-DC Regulator
LM2830 TI-LM2830_15 Datasheet
1Mb / 37P
[Old version datasheet]   LM2830/-Q1 High-Frequency 1.0-A Load Step-Down DC-DC Regulator
logo
National Semiconductor ...
LM2736 NSC-LM2736 Datasheet
444Kb / 22P
   Thin SOT23 750mA Load Step-Down DC-DC Regulator
LM2734 NSC-LM2734 Datasheet
459Kb / 22P
   Thin SOT23 1A Load Step-Down DC-DC Regulator
LM2734Z NSC-LM2734Z Datasheet
775Kb / 9P
   Thin SOT23 1A Load Step-Down DC-DC 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


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
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com