Zakładka z wyszukiwarką danych komponentów |
|
LM25019SDX Arkusz danych(PDF) 10 Page - Texas Instruments |
|
LM25019SDX Arkusz danych(HTML) 10 Page - Texas Instruments |
10 / 28 page FB SW L1 COUT RFB2 VOUT RC LM25019 + RFB1 VOUT (low ripple) RFB2 + RFB1 VOUT = 1.225V x RFB1 OUT SW 11 ON V f 9 10 R u u LM25019 SNVS952E – DECEMBER 2012 – REVISED NOVEMBER 2015 www.ti.com 7.3 Feature Description 7.3.1 Control Overview The LM25019 buck regulator employs a control principle based on a comparator and a one-shot on-timer, with the output voltage feedback (FB) compared to an internal reference (1.225 V). If the FB voltage is below the reference the internal buck switch is turned on for the one-shot timer period, which is a function of the input voltage and the programming resistor (RON). Following the on-time the switch remains off until the FB voltage falls below the reference, but never before the minimum off-time forced by the minimum off-time one-shot timer. When the FB pin voltage falls below the reference and the minimum off-time one-shot period expires, the buck switch is turned on for another on-time one-shot period. This will continue until regulation is achieved and the FB voltage is approximately equal to 1.225 V (typ). In a synchronous buck converter, the low-side (sync) FET is on when the high-side (buck) FET is off. The inductor current ramps up when the high-side switch is on and ramps down when the high-side switch is off. There is no diode emulation feature in this IC, and therefore, the inductor current may ramp in the negative direction at light load. This causes the converter to operate in continuous conduction mode (CCM) regardless of the output loading. The operating frequency remains relatively constant with load and line variations. The operating frequency can be calculated as shown in Equation 1. (1) The output voltage (VOUT) is set by two external resistors (RFB1, RFB2). The regulated output voltage is calculated as shown in Equation 2. (2) This regulator regulates the output voltage based on ripple voltage at the feedback input, requiring a minimum amount of ESR for the output capacitor (COUT). A minimum of 25 mV of ripple voltage at the feedback pin (FB) is required for the LM25019. In cases where the capacitor ESR is too small, additional series resistance may be required (RC in Figure 11). For applications where lower output voltage ripple is required the output can be taken directly from a low ESR output capacitor, as shown in Figure 11. However, RC slightly degrades the load regulation. Figure 11. Low Ripple Output Configuration 7.3.2 VCC Regulator The LM25019 device contains an internal high-voltage linear regulator with a nominal output of 7.6 V. The input pin (VIN) can be connected directly to the line voltages up to 48 V. The VCC regulator is internally current limited to 30 mA. The regulator sources current into the external capacitor at VCC. This regulator supplies current to internal circuit blocks including the synchronous MOSFET driver and the logic circuits. When the voltage on the VCC pin reaches the UVLO threshold of 4.5 V, the IC is enabled. The VCC regulator contains an internal diode connection to the BST pin to replenish the charge in the gate drive boot capacitor when SW pin is low. At high input voltages, the power dissipated in the high-voltage regulator is significant and can limit the overall achievable output power. As an example, with the input at 48 V and switching at high frequency, the VCC regulator may supply up to 7 mA of current resulting in 48 V × 7 mA = 336 mW of power dissipation. If the VCC voltage is driven externally by an alternate voltage source, between 8.55 V and 13 V, the internal regulator is disabled. This reduces the power dissipation in the IC. 10 Submit Documentation Feedback Copyright © 2012–2015, Texas Instruments Incorporated Product Folder Links: LM25019 |
Podobny numer części - LM25019SDX |
|
Podobny opis - LM25019SDX |
|
|
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 |