The MAX8685 family charges high-voltage photoflash capacitors quickly, while limiting peak drain from the battery, through an efficient flyback switching regulator. The internal n-channel MOSFET improves efficiency over competing bipolar designs by lowering switch-voltage dropout. An integrated insulated gate bipolar transistor (IGBT) driver enables flash discharge and reduces external component count. The device includes an open-drain active-low DONE output to indicate when the photoflash voltage has reached regulation. The device automatically refreshes the output voltage every 16s, thus efficiently maintains the capacitor charge level with minimum battery drain.
The MAX8685A/MAX8685F feature an undervoltage input (UVI) monitor. UVI monitors the supply voltage and suspends switching if the input voltage drops below a programmed threshold. The MAX8685A/MAX8685F also feature a voltage-monitor output that provides a scaled replica of the output voltage. The voltage-monitor output is used for interfacing with a microprocessor's internal A/D converter to assist in implementing red-eye reduction.
The MAX8685C/MAX8685D, with fixed peak-primary current limits of 1A and 1.6A, respectively, are offered in a 2mm x 3mm, 8-pin TDFN package. The MAX8685A/MAX8685F, with resistor-programmable current limits of up to 2A (max) and 2.6A (max), respectively, are offered in a 3mm x 3mm, 14-pin TDFN package. All devices operate over the -40°C to +85°C temperature range.
