LT1309

The LT1309 is a DC/DC converter that substantially reduces the size of the 12V power supply used for flash memory programming. The LT1309 operates at 500KHz switching frequency, permitting extremely small, low-value, surface mount inductors and capacitors to be used with the device. A complete 5V or 3.3V to 12V/60mA DC/DC converter requires just two capacitors, one 10ÁH inductor and one diode along with the LT1309. Voltage conversion for all Intel Flash memory devices is easily accomplished with the LT1309. The device is also useful for host-side 12V VPP generation and Type II and III flash memory card internal 12V VPP generation from a 3.3V supply.
To simplify the interface to external control logic, the LT1309 includes a VPP VALID comparator. The comparator's VPP VALID logic output goes low when the output voltage is within 5% of 12V, providing a clear indication that the VPP voltage is sufficient to program 12V flash memory. A soft-start feature limits supply current inrush during turn-on, eliminating input supply voltage drops due to high current surges. A resistor and capacitor connected to the soft start pin determine the soft start timing.
The LT1309 uses Burst Mode* operation which combines with an on-chip 0.5 ampere, 300mV switch to produce 85% peak efficiency when boosting 5V to 12V. Quiescent current is just 650 microamperes. Shutdown of the LT1309 is achieved by pulling the active-low on/off pin to ground reducing quiescent current to just 9ÁA.