- 您现在的位置：买卖IC网 > PDF目录240279 > L6996DTR (STMICROELECTRONICS) SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO24 PDF资料下载
参数资料
| 型号： | L6996DTR |
| 厂商： | STMICROELECTRONICS |
| 元件分类： | 稳压器 |
| 英文描述： | SWITCHING CONTROLLER, 1000 kHz SWITCHING FREQ-MAX, PDSO24 |
| 封装： | MO-153AD, TSSOP-24 |
| 文件页数： | 5/26页 |
| 文件大小： | 272K |
| 代理商： | L6996DTR |
13/26
L6996
continuous mode at high load. The transition from PFM to PWM occurs when load current is around half the
inductor current ripple. This threshold value depends on VIN, L, and VOUT. Note that the higher the inductor val-
ue is, the smaller the threshold is. On the other hand, the bigger the inductor value is, the slower the transient
response is. In PFM mode the frequency changes, with the output current changing, more than in PWM mode;
in fact if the output current increase, the output voltage decreases more quickly; so the successive turn-on ar-
rives before, increasing the switching frequency. The PFM waveforms may appear more noisy and asynchro-
nous than normal operation, but this is normal behaviour mainly due to the very low load. The NOSKIP feature
cannot be disabled.
1.4 Softstart
If the supply voltages are already applied, the SHDN pin gives the start-up. The system starts with the high side
MOSFET off and the low side MOSFET on. After the SHDN pin is turned on the SS pin voltage begins to in-
crease and the system starts to switch. The softstart is realized by gradually increasing the current limit thresh-
old to avoid output overvoltage. The active soft start range (where the output current limit increase linearly)
starts from 0.6V to 1.5V. In this range an internal current source (5
A typ) charges the capacitor on the SS pin.
The reference current (for the current limit comparator) forced through ILIM pin is proportional to SS pin voltage
and it saturates at 5
A (typ.) when SS voltage is close to 1.5V; so the maximum current limit is active. Output
protections like undervoltage is disabled until SS pin voltage reaches 1.5V, instead the overvoltage is always
present.
Once the SS pin voltage reaches the 1.5V value, the voltage on SS pin doesn’t impact the system operation
anymore. If the SHDN pin is turned on before the supplies, the correct start-up sequence is the following: first
turn-on the power section and after the logic section (VCC pin).
Figure 15. Soft-start diagram
1.5 Current limit
The current limit comparator senses inductor current through the sense resistor when the low side MOSFET is
on and compares this value with the ILIM pin voltage. While the current is above the prefixed value, the control
inhibits the one-shot start.
To properly set the current limit threshold, it should be noted that this is a valley current limit. Average current
depends on the inductor value, VIN eVOUT.
Eq 10
IOUTCL =IMAX_VALLEY + IL /2
Time
0.6V
Maximum current limit
Soft-star t active range
5
A
4.1V
1.5V
Ilim current
Vss
相关PDF资料 |
PDF描述 |
|---|---|
| LTC6604IUFF-15#TRPBF | SPECIALTY ANALOG CIRCUIT, PQCC34 |
| LM22671QMR-ADJ | 0.9 A SWITCHING REGULATOR, 600 kHz SWITCHING FREQ-MAX, PDSO8 |
| LTC2991CMS#TRPBF | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| LS4501-7ERD3TB1 | 1-OUTPUT 100 W AC-DC PWR FACTOR CORR MODULE |
| LK1501-7EPD5TB1 | 1-OUTPUT 150 W AC-DC REG PWR SUPPLY MODULE |
相关代理商/技术参数 |
参数描述 |
|---|---|
| L6997 | 制造商:STMICROELECTRONICS 制造商全称:STMicroelectronics 功能描述:STEP DOWN CONTROLLER FOR LOW VOLTAGE OPERATIONS |
| L6997-28 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT |
| L6997-5 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT; Accessory Type:Tuning Element; For Use With:High Quality Variable Reactance Tuning Microwave Cavities, Filters & other Resonant Structures |
| L6997-9 | 制造商:Johanson Manufacturing 功能描述:TUNING ELEMENT |
| L6997D | 功能描述:DC/DC 开关控制器 Adjustable Step-Down RoHS:否 制造商:Texas Instruments 输入电压:6 V to 100 V 开关频率: 输出电压:1.215 V to 80 V 输出电流:3.5 A 输出端数量:1 最大工作温度:+ 125 C 安装风格: 封装 / 箱体:CPAK |
发布紧急采购，3分钟左右您将得到回复。