数据搜索系统,热门电子元器件搜索 |
|
LT1641-2 数据表(PDF) 28 Page - Linear Technology |
|
LT1641-2 数据表(HTML) 28 Page - Linear Technology |
28 / 36 page LTC4252-1/LTC4252-2 LTC4252A-1/LTC4252A-2 28 425212fd APPLICATIONS INFORMATION Analog Current Limit and Fast Current Limit In Figure 17a, when SENSE exceeds VACL, GATE is regulated by the analog current limit amplifier loop. When SENSE drops below VACL, GATE is allowed to pull up. In Figure 17b, when a severe fault occurs, SENSE exceeds VFCL and GATE immediately pulls down until the analog current amplifier establishes control. If the severe fault causes VOUT to exceed VDRNCL, the DRAIN pin is clamped at VDRNCL. IDRN flows into the DRAIN pin and is multiplied by 8. This extra current is added to the TIMER pull-up current of 230μA. This accelerated TIMER current of [230μA+8 • IDRN] produces a shorter circuit breaker fault delay. Careful selection of CT, RD and MOSFET can help prevent SOA damage in a low impedance fault condition. Soft-Start If the SS pin is not connected, this pin defaults to a linear voltage ramp, from 0V to 2.2V in about 180μs (or 0V to 1.4V in 230μs for the LTC4252A) at GATE start-up, as shown in Figure 18a. If a soft-start capacitor, CSS, is con- nected to this SS pin, the soft-start response is modified from a linear ramp to an RC response (Equation 6), as shown in Figure 18b. This feature allows load current to slowly ramp-up at GATE start-up. Soft-start is initiated at time point 3 by a TIMER transition from VTMRH to VTMRL (time points 1 to 2) or by the OV pin falling below the VOVLO threshold after an OV condition. When the SS pin is below 0.2V, the analog current limit amplifier holds GATE low. Above 0.2V, GATE is released and 58μA ramps up the compensation network and GATE capacitance at time point 4. Meanwhile, the SS pin voltage continues to ramp up. When GATE reaches the MOSFET’s threshold, the MOSFET begins to conduct. Due to the MOSFET’s high gm, the MOSFET current quickly reaches the soft-start control value of VACL(t) (Equation 7). At time point 6, the GATE voltage is controlled by the current limit amplifier. The soft-start control voltage reaches the circuit breaker voltage, VCB, at time point 7 and the circuit breaker TIMER activates. As the load capacitor nears full charge, load TIMER GATE SENSE VOUT VACL VCB SS DRAIN VTMRH DRN 425212 F17 PWRGD 5.8μA 5.8μA TIMER GATE SENSE VOUT VACL VCB VFCL SS DRAIN VTMRH VDRNCL DRN PWRGD 12 14 3 2 CB TIMES OUT Figure 17. Current Limit Behavior (All Waveforms Are Referenced to VEE) (17a) Analog Current Limit Fault (17b) Fast Current Limit Fault |
类似零件编号 - LT1641-2 |
|
类似说明 - LT1641-2 |
|
|
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 |