 |
Datenblatt-Suchmaschine für elektronische Bauteile |
|
|
Datenblatt-Suchmaschine für elektronische Bauteile |
|
The question interval is too short.
Please try again in a few seconds.
Hello, Please ask a question about LM3478_09 Datasheet
# Example questions:
➢ What happens when the input voltage crosses the 7.2v internal bias threshold in a boost converter?
➢ What condition must be met to ensure a boost converter operates in continuous conduction mode (ccm), and how does this relate to the inductor current ripple (δil) and average inductor current (il)?
➢ What is the primary function of slope compensation in current mode control, and how can it be adjusted using an external resistor?
| Part No. | LM3478_09 |
| Manufacturer | NSC |
| Size | 507 Kbytes |
| Pages | 22 pages |
| Description | High Efficiency Low-Side N-Channel Controller for Switching Regulator |
1. LM3478: Overview and Functionality
️· What it is: A current-mode boost converter IC.
️· Primary Use: Boosting low input voltages to higher output voltages.
️· Modes of Operation:
- Continuous Conduction Mode (CCM): Preferred for higher efficiency and lower EMI. (The focus of most of the documentation).
- Discontinuous Conduction Mode (DCM): Less common, requires different design considerations.
️· Key Features:
- Adjustable Switching Frequency: 100kHz - 1MHz, using an external resistor.
- Shutdown Function: Pin can be driven high (>1.35V) to disable switching, reducing power consumption to < 10 uA.
- Short-Circuit Protection: Reduces switching frequency by a factor of 5 upon detecting a short circuit condition (voltage across the sense resistor exceeds 343mV).
- Slope Compensation: Built-in to prevent sub-harmonic oscillation (a potential instability at higher duty cycles). External slope compensation can be added if needed.
2. Design Considerations – Boost Converter
️· Duty Cycle (D):
- Ideal: D = 1 - (V<sub>in</sub> / V<sub>out</sub>)
- Realistic: D = 1 - ((V<sub>in</sub> - V<sub>q</sub>) / (V<sub>out</sub> + V<sub>d</sub>)) (accounting for MOSFET and diode voltage drops)
️· Inductor Selection:
- Importance: Critical for CCM operation.
- Inductor Current Ripple (ΔI<sub>L</sub>): Typically kept to 30% of average inductor current (I<sub>L</sub>).
- Peak Inductor Current (I<sub>L(peak)</sub>): Must be accounted for when selecting inductor core size to prevent saturation.
■ I<sub>L(peak)</sub> = Average I<sub>L</sub> + ΔI<sub>L</sub> (Where average I<sub>L</sub> is Iout/(1-D) )
️· Slope Compensation:
- Purpose: Prevents sub-harmonic oscillation (instability at higher duty cycles).
- Adjustment: Can be adjusted with an external resistor (R<sub>SL</sub>) to fine-tune performance.
3. Important Formulas
️· Duty Cycle: D = 1 - ((V<sub>in</sub> - V<sub>q</sub>) / (V<sub>out</sub> + V<sub>d</sub>))
️· Peak Inductor Current: I<sub>L(peak)</sub> = Iout/(1-D) + ΔI<sub>L</sub>
️· Slope Compensation: S<sub>e</sub> = (V<sub>SL</sub> + (K x R<sub>SL</sub>)) x f<sub>s</sub> (where K is a factor typically around 40µA)
4. Key Pins & Functions
️· Frequency Adjust/Shutdown (FA/SD): Used for both adjusting the switching frequency and implementing the shutdown function. A high signal (>1.35V) disables switching.
️· Isen: Sense Pin, monitors inductor current.
1. LM3478: Overview and Functionality
️· What it is: A current-mode boost converter IC.
️· Primary Use: Boosting low input voltages to higher output voltages.
️· Modes of Operation:
- Continuous Conduction Mode (CCM): Preferred for higher efficiency and lower EMI. (The focus of most of the documentation).
- Discontinuous Conduction Mode (DCM): Less common, requires different design considerations.
️· Key Features:
- Adjustable Switching Frequency: 100kHz - 1MHz, using an external resistor.
- Shutdown Function: Pin can be driven high (>1.35V) to disable switching, reducing power consumption to < 10 uA.
- Short-Circuit Protection: Reduces switching frequency by a factor of 5 upon detecting a short circuit condition (voltage across the sense resistor exceeds 343mV).
- Slope Compensation: Built-in to prevent sub-harmonic oscillation (a potential instability at higher duty cycles). External slope compensation can be added if needed.
2. Design Considerations – Boost Converter
️· Duty Cycle (D):
- Ideal: D = 1 - (V<sub>in</sub> / V<sub>out</sub>)
- Realistic: D = 1 - ((V<sub>in</sub> - V<sub>q</sub>) / (V<sub>out</sub> + V<sub>d</sub>)) (accounting for MOSFET and diode voltage drops)
️· Inductor Selection:
- Importance: Critical for CCM operation.
- Inductor Current Ripple (ΔI<sub>L</sub>): Typically kept to 30% of average inductor current (I<sub>L</sub>).
- Peak Inductor Current (I<sub>L(peak)</sub>): Must be accounted for when selecting inductor core size to prevent saturation.
■ I<sub>L(peak)</sub> = Average I<sub>L</sub> + ΔI<sub>L</sub> (Where average I<sub>L</sub> is Iout/(1-D) )
️· Slope Compensation:
- Purpose: Prevents sub-harmonic oscillation (instability at higher duty cycles).
- Adjustment: Can be adjusted with an external resistor (R<sub>SL</sub>) to fine-tune performance.
3. Important Formulas
️· Duty Cycle: D = 1 - ((V<sub>in</sub> - V<sub>q</sub>) / (V<sub>out</sub> + V<sub>d</sub>))
️· Peak Inductor Current: I<sub>L(peak)</sub> = Iout/(1-D) + ΔI<sub>L</sub>
️· Slope Compensation: S<sub>e</sub> = (V<sub>SL</sub> + (K x R<sub>SL</sub>)) x f<sub>s</sub> (where K is a factor typically around 40µA)
4. Key Pins & Functions
️· Frequency Adjust/Shutdown (FA/SD): Used for both adjusting the switching frequency and implementing the shutdown function. A high signal (>1.35V) disables switching.
️· Isen: Sense Pin, monitors inductor current.
| Part No. | LM3478_09 |
| Manufacturer | NSC |
| Size | 507 Kbytes |
| Pages | 22 pages |
| Description | High Efficiency Low-Side N-Channel Controller for Switching Regulator |
| War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Link zum Datenblatt | Linktausch | Hersteller All Rights Reserved©Alldatasheet.com |
| 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 |
German ▼ 
English
Chinese
Japanese
Russian
Korean
Spanish
French
Italian
Portuguese
Polish
Vietnamese
Indian
Mexican
British
New Zealand