Zakładka z wyszukiwarką danych komponentów |
|
LM2621MM Arkusz danych(PDF) 7 Page - Texas Instruments |
|
LM2621MM Arkusz danych(HTML) 7 Page - Texas Instruments |
7 / 17 page LM2621 www.ti.com SNVS033C – MAY 2004 – REVISED MARCH 2005 Because of this type of control scheme, the quiescent current is inherently very low. At light loads the gated oscillator control scheme offers a much higher efficiency compared to the conventional PWM control scheme. Figure 14. Typical Step-Up Regulator Waveforms LOW VOLTAGE START-UP The LM2621 can start-up from input voltages as low as 1.1V. On start-up, the control circuitry switches the N- channel MOSFET continuously at 70% duty cycle until the output voltage reaches 2.5V. After this output voltage is reached, the normal step-up regulator feedback and gated oscillator control scheme take over. Once the device is in regulation it can operate down to a 0.65V input, since the internal power for the IC can be boot- strapped from the output using the VDD pin. SHUTDOWN The LM2621 features a shutdown mode that reduces the quiescent current to less than a ensured 2.5µA over temperature. This extends the life of the battery in battery powered applications. During shutdown, all feedback and control circuitry is turned off. The regulator's output voltage drops to one diode drop below the input voltage. Entry into the shutdown mode is controlled by the active-low logic input pin EN (Pin 2). When the logic input to this pin pulled below 0.15VDD, the device goes into shutdown mode. The logic input to this pin should be above 0.7VDD for the device to work in normal step-up mode. OUTPUT VOLTAGE RIPPLE FREQUENCY A major component of the output voltage ripple is due to the hysteresis used in the gated oscillator control scheme. The frequency of this voltage ripple is proportional to the load current. The frequency of this ripple does not necessitate the use of larger inductors and capacitors however, since the size of these components is determined by the switching frequency of the oscillator which can be set upto 2MHz using an external resistor. INTERNAL CURRENT LIMIT AND THERMAL PROTECTION An internal cycle-by-cycle current limit serves as a protection feature. This is set high enough (2.85A typical, approximately 4A maximum) so as not to come into effect during normal operating conditions. An internal thermal protection circuitry disables the MOSFET power switch when the junction temperature (TJ) exceeds about 160°C. The switch is re-enabled when TJ drops below approximately 135°C. Copyright © 2004–2005, Texas Instruments Incorporated Submit Documentation Feedback 7 Product Folder Links: LM2621 |
Podobny numer części - LM2621MM |
|
Podobny opis - LM2621MM |
|
|
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 |
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 |