Electronic Components Datasheet Search |
|
LM20144QMHE/NOPB Datasheet(PDF) 11 Page - Texas Instruments |
|
|
LM20144QMHE/NOPB Datasheet(HTML) 11 Page - Texas Instruments |
11 / 30 page LM20144 www.ti.com SNVS529G – OCTOBER 2007 – REVISED MARCH 2013 OPERATION DESCRIPTION GENERAL The LM20144 switching regulator features all of the functions necessary to implement an efficient low voltage buck regulator using a minimum number of external components. This easy to use regulator features two integrated switches and is capable of supplying up to 4A of continuous output current. The regulator utilizes peak current mode control with nonlinear slope compensation to optimize stability and transient response over the entire output voltage range. Peak current mode control also provides inherent line feed-forward, cycle-by-cycle current limiting and easy loop compensation. The switching frequency can be varied from 500 kHz to 1.5 MHz. The device can operate at high switching frequency allowing use of a small inductor while still achieving high efficiency. The precision internal voltage reference allows the output to be set as low as 0.8V. Fault protection features include: current limiting, thermal shutdown, over voltage protection, and shutdown capability. The device is available in the HTSSOP 16-pin package featuring an exposed pad to aid thermal dissipation. The LM20144 can be used in numerous applications to efficiently step-down from a 5V or 3.3V bus. The typical application circuit for the LM20144 is shown in Figure 28 in the design guide. PRECISION ENABLE The enable (EN) pin allows the output of the device to be enabled or disabled with an external control signal. This pin is a precision analog input that enables the device when the voltage exceeds 1.18V (typical). The EN pin has 66 mV of hysteresis and will disable the output when the enable voltage falls below 1.11V (typical). If the EN pin is not used, it should be connected to VIN. Since the enable pin has a precise turn-on threshold it can be used along with an external resistor divider network from VIN to configure the device to turn-on at a precise input voltage. The precision enable circuitry will remain active even when the device is disabled. PEAK CURRENT MODE CONTROL In most cases, the peak current mode control architecture used in the LM20144 only requires two external components to achieve a stable design. The compensation can be selected to accommodate any capacitor type or value. The external compensation also allows the user to set the crossover frequency and optimize the transient performance of the device. For duty cycles above 50% all current mode control buck converters require the addition of an artificial ramp to avoid sub-harmonic oscillation. This artificial linear ramp is commonly referred to as slope compensation. What makes the LM20144 unique is the amount of slope compensation will change depending on the output voltage. When operating at high output voltages the device will have more slope compensation than when operating at lower output voltages. This is accomplished in the LM20144 by using a non-linear parabolic ramp for the slope compensation. The parabolic slope compensation of the LM20144 is much better than the traditional linear slope compensation because it optimizes the stability of the device over the entire output voltage range. CURRENT LIMIT The precise current limit of the LM20123 is set at the factory to be within 10% over the entire operating temperature range. This enables the device to operate with smaller inductors that have lower saturation currents. When the peak inductor current reaches the current limit threshold, an over current event is triggered and the internal high-side FET turns off and the low-side FET turns on allowing the inductor current to ramp down until the next switching cycle. For each sequential over-current event, the reference voltage is decremented and PWM pulses are skipped resulting in a current limit that does not aggressively fold back for brief over-current events, while at the same time providing frequency and voltage foldback protection during hard short circuit conditions. SOFT-START AND VOLTAGE TRACKING The SS/TRK pin is a dual function pin that can be used to set the start up time or track an external voltage source. The start up or Soft-Start time can be adjusted by connecting a capacitor from the SS/TRK pin to ground. The Soft-Start feature allows the regulator output to gradually reach the steady state operating point, thus reducing stresses on the input supply and controlling start up current. If no Soft-Start capacitor is used the device defaults to the internal Soft-Start circuitry resulting in a start up time of approximately 1ms. For applications that require a monotonic start up or utilize the PGOOD pin, an external Soft-Start capacitor is recommended. The SS/TRK pin can also be set to track an external voltage source. The tracking behavior can be adjusted by two external resistors connected to the SS/TRK pin as shown in Figure 33. in the design guide. Copyright © 2007–2013, Texas Instruments Incorporated Submit Documentation Feedback 11 Product Folder Links: LM20144 |
Similar Part No. - LM20144QMHE/NOPB |
|
Similar Description - LM20144QMHE/NOPB |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List 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 |