数据搜索系统,热门电子元器件搜索 |
|
LM34919 数据表(PDF) 10 Page - Texas Instruments |
|
LM34919 数据表(HTML) 10 Page - Texas Instruments |
10 / 21 page 0.64A Load Current Increases IPK IOCL IO 'I Normal Operation Current Limited STOP RUN RON/SD Input Voltage LM34919 VIN RON LM34919 SNOSAY2D – MAY 2007 – REVISED JUNE 2008 www.ti.com Figure 5. Shutdown Implementation Current Limit Current limit detection occurs during the off-time by monitoring the recirculating current through the free-wheeling diode (D1). Referring to the Block Diagram, when the buck switch is turned off the inductor current flows through the load, into SGND, through the sense resistor, out of ISEN and through D1. If that current exceeds 0.64A the current limit comparator output switches to delay the start of the next on-time period. The next on-time starts when the current out of ISEN is below 0.64A and the voltage at FB is below 2.5V. If the overload condition persists causing the inductor current to exceed 0.64A during each on-time, that is detected at the beginning of each off-time. The operating frequency is lower due to longer-than-normal off-times. Figure 6 shows the inductor current waveform. During normal operation the load current is Io, the average of the ripple waveform. When the load resistance decreases the current ratchets up until the lower peak reaches 0.64A. During the Current Limited portion of Figure 6, the current ramps down to 0.64A during each off-time, initiating the next on-time (assuming the voltage at FB is <2.5V). During each on-time the current ramps up an amount equal to: ΔI = (VIN - VOUT) x tON / L1 (7) During this time the LM34919 is in a constant current mode, with an average load current (IOCL) equal to 0.64A + ΔI/2. Generally, in applications where the switching frequency is higher than ≊300 kHz and uses a small value inductor, the higher dl/dt of the inductor's ripple current results in an effectively lower valley current limit threshold due to the response time of the current limit detection circuit. However, since the small value inductor results in a relatively high ripple current amplitude ( ΔI in Figure 6), the load current (IOCL) at current limit is typically in excess of 640 mA. Figure 6. Inductor Current - Current Limit Operation 10 Submit Documentation Feedback Copyright © 2007–2008, Texas Instruments Incorporated Product Folder Links: LM34919 |
类似零件编号 - LM34919_14 |
|
类似说明 - LM34919_14 |
|
|
链接网址 |
隐私政策 |
ALLDATASHEETCN.COM |
ALLDATASHEET是否为您带来帮助? [ DONATE ] |
关于 Alldatasheet | 广告服务 | 联系我们 | 隐私政策 | 链接交换 | 制造商名单 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 |