công cụ tìm kiếm bảng dữ liệu linh kiện điện tử |
|
LM2759SD/NOPB bảng dữ liệu(PDF) 9 Page - Texas Instruments |
|
|
LM2759SD/NOPB bảng dữ liệu(HTML) 9 Page - Texas Instruments |
9 / 22 page LM2759 www.ti.com SNVS577D – JUNE 2008 – REVISED MAY 2013 APPLICATION INFORMATION CIRCUIT DESCRIPTION The LM2759 is an adaptive CMOS charge pump with gains of 1x, 1.5x, and 2x, optimized for driving Flash LEDs in camera phones and other portable applications. It provides a constant current of up to 1A (typ.) for Flash mode and 180 mA (typ.) for Torch mode. The LM2759 has selectable modes including Flash, Torch, Indicator and Shutdown. Flash mode for the LM2759 can also be enabled via the Strobe input pin. The LED is driven from VOUT and connected to the current sink. The LED drive current and operating modes are programmed via an I2C compatible interface. The LM2759 adaptively selects the next highest gain mode when needed to maintain the programmed LED current level. To prevent a high battery load condition during a simultaneous RF PA transmission and Flash event, LM2759 has a Flash interrupt pin (TX) to reduce the LED current to the programmed Torch current level for the duration of the RF PA transmission pulse. CHARGE PUMP AND GAIN TRANSITIONS The input to the 1x, 1.5x, 2x charge pump is connected to the VIN pin, and the loosely regulated output of the charge pump is connected to the VOUT pin. In 1x mode, as long as the input voltage is less than 4.7V (typ.), the output voltage is approximately equal to the input voltage. When the input voltage is over 4.7V (typ.) the output voltage is regulated to 4.7V (typ.). In 1.5x mode, the output voltage is regulated to 4.7V (typ.) over entire input voltage range. For the gain of 2x, the output voltage is regulated to 5.1V (typ.). When under load, the voltage at VOUT can be less than the target regulation voltage while the charge pump is still in closed loop operation. This is due to the load regulation topology of the LM2759. The charge pump’s gain is selected according to the headroom voltage across the current sink of LM2759. When the headroom voltage VGDX (at the LED cathode) drops below 350 mV (typ.) the charge pump gain transitions to the next available higher gain mode. Once the charge pump transitions to a higher gain, it will remain at that gain for as long as the device remains enabled. Shutting down and then re-enabling the device resets the gain mode to the minimum gain required to maintain the load. SOFT START The LM2759 contains internal soft-start circuitry to limit inrush currents when the part is enabled. Soft start is implemented internally with a controlled turn-on of the internal voltage reference. CURRENT LIMIT PROTECTION The LM2759 charge pump contains current limit protection circuitry that protects the device during VOUT fault conditions where excessive current is drawn. Output current is limited to 1.4A typically. LOGIC CONTROL PINS LM2759 has two asynchronous logic pins, Strobe and TX. These logic inputs function according to the table below: TX STROBE FUNCTION 0 0 Current I2C programmed state (Off, Torch, Flash, Indicator) 1 0 Current I2C programmed state (Off, Torch, Flash, Indicator). If Flash is enabled via I2C and TX is logic High, the LED current will be at the programmed Torch level. 0 1 Flash Mode (Total LED "ON" Duration limited by Flash Timeout) 1 1 Torch Mode (Total LED "ON" Duration limited by Flash Timeout) Copyright © 2008–2013, Texas Instruments Incorporated Submit Documentation Feedback 9 Product Folder Links: LM2759 |
Số phần tương tự - LM2759SD/NOPB |
|
Mô tả tương tự - LM2759SD/NOPB |
|
|
Link URL |
Chính sách bảo mật |
ALLDATASHEET.VN |
Cho đến nay ALLDATASHEET có giúp ích cho doanh nghiệp của bạn hay không? [ DONATE ] |
Alldatasheet là | Quảng cáo | Liên lạc với chúng tôi | Chính sách bảo mật | Trao đổi link | Tìm kiếm theo nhà sản xuất 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 |