ADI ADP2102/1653 LED驱动方案
| ADP2102低静态电流降压式DC/DC变换器和ADP1653 白色LED闪光灯驱动器都属于电源管理集成电路(IC)，它们适合于便携式手持应用，例如无线手机、数码照相机和其它应用。这两款芯片以高达95%的电源效率显著延长了电池寿命，并且配合节能模式在轻负载条件下降低了开关频率。此外，它们还提供过压和欠压锁定以及软启动功能，有助于减少或消除启动期间电池过度放电或启动电流过冲造成的损害影响。当射频（RF）发射期间放大器的电流突然增加时，ADP1653提供一种独特的功能——当在RF传输时，Tx masking启动，降低闪光灯LED的消耗电流。这两款芯片在小尺寸封装中实现了这些附加的性能。本文介绍了ADP2102和ADP1653的主要性能，应用电路以及ADP1653闪光LED驱动器评估板中主板和子板的详细电路图。 1． The ADP2102 is a synchronous step-down dc-to-dc converter that converts a 2.7 V to 5.5 V unregulated input voltage to a lower regulated output voltage with up to 95% efficiency and 1% accuracy. The low duty cycle capability of the ADP2102 is ideal for USB applications or 5 V systems that power up submicron subvolt processor cores. Its 3 MHz typical operating frequency and excel-lent transient response allow the use of small, low cost 1 μH inductors and 2.2 μF ceramic capacitors. At medium-to-high load currents, it uses a current mode, pseudofixed frequency pulse-width modulation to extend battery life. To ensure the longest battery life in portable applications, the ADP2102 has a power save mode (PSM) that reduces the switching frequency under light load conditions to significantly reduce quiescent current. The ADP2102 is available in both fixed and adjustable output voltage options with 600 mA maximum output current. The preset output voltage options voltage are 1.875 V, 1.8 V, 1.5 V, 1.375 V, 1.25 V, 1.2 V, 1.0 V, and 0.8 V. The adjustable voltage option is available from 0.8 V to 3.3 V. The ADP2102 requires only three external components and consumes 0.01 μA in shutdown mode. The ADP2102 is available in an 8-lead LFCSP package and is specified for the −40 °C to +85 °C temperature range. ADP2102主要特性： Input voltage range: 2.7 V to 5.5 V 600 mA maximum load current 95% efficiency Low duty cycle operation Only 3 tiny external ceramic components 3 MHz typical operating frequency Fixed output voltage from 0.8 V to 1.875 V Adjustable output voltage up to 3.3 V 0.01 μA shutdown supply current Automatic power save mode Internal synchronous rectifier Internal soft start Internal compensation Enable/shutdown logic input Undervoltage lockout Current limit protection Thermal shutdown Small 8-lead, 3 mm × 3 mm LFCSP package ADP2102主要应用： USB powered devices WLAN and gateways Point of loads Processor core power from 5 V Digital cameras PDAs and palmtop computers Portable media players, GPS 电型应用电路：  图1。 ADP2102-FXD (0 mA ≤ ILOAD ≤ 300 mA)  图2。 ADP2102-FXD (0 mA ≤ ILOAD ≤ 600 mA) EVALUATION BOARD SCHEMATICS  图3。ADP2102-1.2-EVALZ 电路图， VOUT = 1.2 V  图4。ADP2102-EVALZ 电路图， VOUT = 3.3 V 2． ADP1653闪光LED驱动器 The ADP1653 is a very compact, high efficiency, high power, camera flash LED driver optimized for cellular phones. The high efficiency and dynamic LED current control of the device improve flash brightness and picture quality in dimly lit environments. Efficiency peaks at 92% and is higher than charge pump solutions over the Li-Ion battery range. The device has a dual-mode interface that is configurable to 2-bit logic or an I2C interface. The indicator and high power LED currents are programmable with external resistors or through the I2C interface. To maximize overall flash brightness, the ADP1653 offers an input to reduce flash LED current in less than 50 μs, referred to as the Tx mask. Tx masking reduces battery stress by scaling back flash LED current during an RF transmission. The ADP1653 solution requires only four external components in I2C mode and fits in a 6.4 mm × 7.2 mm space. The part inte-grates multiple safety features such as soft start, flash timeout, output current limit, thermal protection, and overvoltage protection. The ADP1653 operates over the −40°C to +125°C junction temperature range. ADP1653主要特性： Small 6.4 mm × 7.2 mm solution 2.2 μH power inductor 92% peak efficiency Tx masking within 50 μs 2.1 A, 12 V power switch Pin-selectable interface: 2-bit logic or I2C Programmable flash and torch current Up to 200 mA in torch mode Up to 500 mA in flash mode Programmable indicator LED current up to 20 mA Programmable timer register: up to 820 ms flash timeout 2.75 V to 5.5 V input voltage range Low noise, 1.2 MHz PWM operation Safety features Interrupt output pin Fault condition register Short-circuit protection Output overvoltage protection Thermal overload protection Integrated current limit and soft start Small 3 mm × 3 mm, 16-lead LFCSP footprint interface Jumpers for measurement of flash LED current and inductor current TxMask for changing flash current on the fly Evaluation software included  图7。评估板中的子板电路图  图8。评估板中的主板电路图 |
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