Os motores de busca de Datasheet de Componentes eletrônicos
  Portuguese  ▼
ALLDATASHEETPT.COM

X  

LM27951SD Folha de dados(PDF) 11 Page - Texas Instruments

Nome de Peças LM27951SD
Descrição Electrónicos  White LED Adaptive 1.5/1 Switched-Capacitor Current Driver
Download  20 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Fabricante Electrônico  TI1 [Texas Instruments]
Página de início  http://www.ti.com
Logo TI1 - Texas Instruments

LM27951SD Folha de dados(HTML) 11 Page - Texas Instruments

Back Button LM27951SD Datasheet HTML 7Page - Texas Instruments LM27951SD Datasheet HTML 8Page - Texas Instruments LM27951SD Datasheet HTML 9Page - Texas Instruments LM27951SD Datasheet HTML 10Page - Texas Instruments LM27951SD Datasheet HTML 11Page - Texas Instruments LM27951SD Datasheet HTML 12Page - Texas Instruments LM27951SD Datasheet HTML 13Page - Texas Instruments LM27951SD Datasheet HTML 14Page - Texas Instruments LM27951SD Datasheet HTML 15Page - Texas Instruments Next Button
Zoom Inzoom in Zoom Outzoom out
 11 / 20 page
background image
11
LM27951
www.ti.com
SNVS416C – NOVEMBER 2005 – REVISED FEBRUARY 2016
Product Folder Links: LM27951
Submit Documentation Feedback
Copyright © 2005–2016, Texas Instruments Incorporated
Capacitors with Y5V or Z5U temperature characteristic are generally not recommended for use with the
LM27951. Capacitors with these temperature characteristics typically have wide capacitance tolerance (80%,
–20%) and vary significantly over temperature (Y5V: 22%, –82% over –30°C to +85°C range; Z5U: 22%, –56%
over 10°C to 85°C range). Under some conditions, a nominal 1-µF Y5V or Z5U capacitor could have a
capacitance of only 0.1 µF. Such detrimental deviation is likely to cause Y5V and Z5U capacitors to fail to meet
the minimum capacitance requirements of the LM27951.
The voltage rating of the output capacitor must be 10 V or more. All other capacitors must have a voltage rating
at or above the maximum input voltage of the application.
8.2.2.3 Parallel Dx Outputs for Increased Current Drive
Outputs D1-4 may be connected together to drive a one or two LEDs at higher currents. In a one LED
configuration, all four parallel current sources of equal value are connected together to drive a single LED. The
LED current programmed must be chosen such that the current provided from each of the outputs is
programmed to 25% of the total desired LED current. For example, if 60 mA is the desired drive current for the
single LED, RSET must be selected so that the current out of each current source is 15 mA. Similarly, if two LEDs
are to be driven by pairing up the D1-4 outputs (that is, D1-2, D3-4), RSET must be selected so that the current out of
each current source output is 50% of the desired LED current.
Connecting the outputs in parallel does not affect the internal operation of the LM27951 and has no impact on
the electrical characteristics and limits previously presented. The available diode output current, maximum diode
voltage, and all other specifications provided in the Electrical Characteristics apply to this parallel output
configuration, just as they do to the standard 4-LED application circuit.
8.2.2.4 Power Efficiency
Efficiency of LED drivers is commonly taken to be the ratio of power consumed by the LEDs (PLED) to the power
drawn at the input of the part (PIN). With a 1.5×/1× charge pump, the input current is equal to the charge pump
gain times the output current (total LED current). For a simple approximation, the current consumed by internal
circuitry can be neglected and the efficiency of the LM27951 can be predicted as follows:
PLED = N × VLED × ILED
(6)
PIN = VIN × IIN
(7)
PIN = VIN × (Gain × N × ILED + IQ)
(8)
E = (PLED / PIN)
(9)
Neglecting IQ results in a slightly higher efficiency prediction, but this impact is no more than a few percentage
points when several LEDs are driven at full power. It is also worth noting that efficiency as defined here is in part
dependent on LED voltage. Variation in LED voltage does not affect power consumed by the circuit and typically
does not relate to the brightness of the LED. For an advanced analysis, it is recommended that power consumed
by the circuit (VIN × IIN) be evaluated rather than power efficiency.
8.2.2.5 Power Dissipation
The power dissipation (PDISSIPATION) and junction temperature (TJ) can be approximated with Equation 10 and
Equation 11. PIN is the power generated by the 1.5×/1× charge pump, PLED is the power consumed by the LEDs,
TAis the ambient temperature, and RθJA is the junction-to-ambient thermal resistance for the 14-pin WSON
package. VIN is the input voltage to the LM27951, VLED is the nominal LED forward voltage, and ILED is the
programmed LED current.
PDISSIPATION = PIN – PLED = [Gain × VIN × (4 x ILED)] − (VLED × 4 × ILED)
(10)
TJ = TA + (PDISSIPATION × RθJA)
(11)
The junction temperature rating takes precedence over the ambient temperature rating. The LM27951 may be
operated outside the ambient temperature rating, so long as the junction temperature of the device does not
exceed the maximum operating rating of 115°C. The maximum ambient temperature rating must be derated in
applications where high power dissipation and/or poor thermal resistance causes the junction temperature to
exceed 115°C.


Nº de peça semelhante - LM27951SD

Fabricante ElectrônicoNome de PeçasFolha de dadosDescrição Electrónicos
logo
National Semiconductor ...
LM27951SD NSC-LM27951SD Datasheet
605Kb / 10P
   White LED Adaptive 1.5X/1X Switched Capacitor Current Driver
LM27951SDX NSC-LM27951SDX Datasheet
605Kb / 10P
   White LED Adaptive 1.5X/1X Switched Capacitor Current Driver
More results

Descrição semelhante - LM27951SD

Fabricante ElectrônicoNome de PeçasFolha de dadosDescrição Electrónicos
logo
National Semiconductor ...
LM27952 NSC-LM27952 Datasheet
521Kb / 8P
   White LED Adaptive 1.5X/1X Switched Capacitor Current Driver
LM27951 NSC-LM27951 Datasheet
605Kb / 10P
   White LED Adaptive 1.5X/1X Switched Capacitor Current Driver
logo
Texas Instruments
LM27952 TI1-LM27952 Datasheet
1,004Kb / 17P
[Old version datasheet]   LM27952 White LED Adaptive 1.5X/1X Switched Capacitor Current Driver
logo
National Semiconductor ...
LM2751 NSC-LM2751 Datasheet
8Kb / 11P
   Regulated 2X, 1.5X Switched Capacitor White LED Driver
logo
Texas Instruments
LM2751SD-B TI-LM2751SD-B Datasheet
1Mb / 19P
[Old version datasheet]   LM2751 Regulated 2X, 1.5X Switched Capacitor White LED Driver
logo
National Semiconductor ...
LM27953 NSC-LM27953 Datasheet
681Kb / 11P
   White LED Driver with Four LED Current Sinks and 3/2x Switched Capacitor Boost
logo
Texas Instruments
LM2751 TI1-LM2751 Datasheet
1Mb / 19P
[Old version datasheet]   LM2751 Regulated 2X, 1.5X Switched Capacitor White LED Driver
logo
Eutech Microelectronics...
EUP2796 EUTECH-EUP2796 Datasheet
263Kb / 9P
   Dual-Display White LED Driver with 3/2X Switched Capacitor Boost
logo
National Semiconductor ...
LM2796 NSC-LM2796 Datasheet
172Kb / 8P
   Dual-Display White LED Driver with 3/2x Switched Capacitor Boost
logo
Texas Instruments
LM27961 TI1-LM27961 Datasheet
267Kb / 16P
[Old version datasheet]   Dual-Display White LED Driver with 3/2x Switched Capacitor Boost
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20


Folha de dados Download

Go To PDF Page


Ligação URL




Privacy Policy
ALLDATASHEETPT.COM
ALLDATASHEET é útil para você?  [ DONATE ] 

Sobre Alldatasheet   |   Publicidade   |   Contato conosco   |   Privacy Policy   |   roca de Link   |   Lista de Fabricantes
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