MIC2870 Evaluation Board 1.5A Synchronous Boost Flash LED Driver 2 with I C Interface General Description Getting Started The MIC2870 is a high-current, high-efficiency flash LED 1. Connect external supply to the VIN terminals. driver for one or two high-brightness camera flash LEDs. Apply desired input voltage to the VIN (J1) and ground (J2) terminals of the evaluation board, paying careful The LED driver current is generated by an integrated attention to polarity and supply range (2.7V to 5.0V). inductive boost converter with 2MHz switching frequency An ammeter may be placed between the power supply which allows the use of very small inductor and output and the input terminal of the evaluation board. Ensure capacitor. These features make the MIC2870 an ideal that the supply voltage is monitored at the input solution for high-resolution camera phone LED flash light terminals. The ammeter and /or power lead resistance driver applications. can reduce the voltage supplied to the input. MIC2870 supports two 750mA white-LEDs (WLEDs) or a 2. Enable/Disable the MIC2870. single 1.5A WLED configuration. When two WLEDs are connected, their currents are matched automatically. The MIC2870 evaluation board has an enable (EN) pin (J5). The MIC2870 is in standby mode when the EN MIC2870 operates in either flash or torch modes that can pin is asserted high. Setting a jumper at TP1 can 2 be controlled through either I C interface or external pins. connect the EN pin to VIN through a pull-high resistor. The brightness in the flash and torch mode can be If this pin is driven low for more than 1s, the IC is adjusted via two external resistors individually. High-speed shutdown. This pin is pulled down by an internal 2 mode I C interface provides a simple control at a clock resistor. Alternatively, the IC can be enabled or speed up to 3.4MHz to support most camera functions 2 disabled by software through I C interface. such as auto-focus, white balance, and image capture. 3. Enable/Disable the torch mode. Datasheets and support documentation are available on The TEN (J3) is the torch mode enable pin. When this Micrels web site at: www.micrel.com. pin is high, the torch mode is initiated. Setting a jumper Requirements at TP4 can connect TEN pin to VIN through a resistor. If this pin is left floating, it is pulled-down internally by a The MIC2870 evaluation board requires a bench input built-in 1A current source when the device is power source that is adjustable from 2.7V to 5.0V and is enabled. Alternatively, the torch mode can be enabled able to deliver greater than 4.5A at 2.7V. 2 or disabled by software through I C interface. Precautions 4. Enable/Disable the flash mode. The evaluation board does not have reverse polarity The FEN (TP2 upper pin) is the flash mode enable pin. protection. Applying a negative voltage across the VIN A low-to-high transition at this pin initiates the flash terminal to GND terminal may damage the device. The mode and the flash mode timer. Setting a jumper at MIC2870 evaluation board is tailored for a Li-ion range TP2 can connect FEN to VIN through a resistor. If this input supply voltage. It should not exceed 5.0V on the pin is left floating, it is pulled-down internally by a built- input. in 1A current source when the device is enabled. Alternatively, the flash mode can be enabled or 2 disabled by software through I C interface. Ordering Information Part Number Description MIC2870YFT EV MIC2870 Evaluation Board 2 MICUSB Dongle EV I C Serial Programmer Board Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC2870 Evaluation Board Getting Started (Continued) 5. Enable/Disable flash inhibit. The FI (TP3 upper pin) is the flash inhibit pin. When this pin is high in flash mode, both LED1 (D1) and LED2 (D2) currents are changed from the flash mode current level to the torch mode current level. When this pin is low, both LED1 (D1) and LED2 (D2) currents are changed from torch mode current level back to the original flash mode current level. Setting a jumper at TP3 can connect FI to VIN through a resistor. If this pin is left floating, it is pulled-down internally by a built- in 1A current source when the device is enabled. 6. Graphic user interface support. Graphical user interface software can be used with the MICUSB Dongle EV allowing configuration and testing of the MIC2870 with a standard computer. For more detail, refer to the Evaluation Software section. Revision 1.2 September 24, 2013 2