Demo Board DC323 Quick Start Guide LTC1751-3.3/5/Adjustable 3.3V, 5V and Adjustable Micropower Charge Pump DESCRIPTION The DC323A demonstrates the small size, low power, ease of use and appropriate layout techniques for the LTC1751-X regulated charge pump. The LTC1751-X can be used wherever step-up voltage conversion is needed in a relatively tight space. The LTC1751- 3.3 converts input voltages of 2.0V to 4.4V to a regulated voltage of 3.3V 4% at up to 80mA. The LTC1751-5 converts input voltages of 2.7V to 5.5V to a regulated voltage of 5.0V 4% at up to 100mA. The adjustable LTC1751 can be programmed to deliver voltages up to twice the available input voltage. OPERATION LTC1751-X Operation The LTC1751-X is a family of regulated micropower voltage doubling charge pump DC/DC converters. The charge pump requires one flying capacitor for the doubling operation, a charge storage capacitor on the output and an input bypass capacitor. The LTC1751-5 can develop up to 100mA (500mW) from an input supply as low as 3V and the LTC1751-3.3 can develop 80mA from a 2.5V input. Extremely low operating current (20A typical) and a low external parts count (one flying capacitor and two small bypass capacitors) make it ideally suited for small, battery-powered applications. The LTC1751- TM 5 operates as a Burst Mode switched capacitor voltage doubler to ensure that the power supply current is extremely low when there is no load present. Burst Mode operation optimizes efficiency by disabling the charge pump whenever the output voltage is in regulation. All LTC1751-X devices have thermal shutdown capability and can survive a continuous short circuit from V to GND. The LTC1751-3.3 and LTC1751-5 have a OUT PGOOD pin that indicates when the output voltage has reached its final value. This pin is useful for signaling to a microcontroller that a peripheral device has been fully powered and is available for use. PGOOD also indicates if the output has an undervoltage fault condition. The adjustable LTC1751 has an FB pin rather than a PGOOD pin and can be programmed to deliver an arbitrary output voltage (up to 2 V ) or current. An optional IN soft-start capacitor may be used at the SS pin to prevent excessive current during start-up. Finally, the /SHDN pin can be used to disable the output or provide PWM level control of the average output voltage. In shutdown, the supply current drops to below 1A. The LTC1751 family is available in an 8-pin MSOP package. PARTS LIST Referenc e Quanti Description Part Number Vendor Phone Number Designat ty or C4 1 1000pF, 50V, NPO Chip 06035A102JAT (0603) AVX (843) 946- Capacitor 0362 C3 1 1F, 10V, X7R Chip LMK212BJ105MG (0805) Taiyo Yuden (408) 573- Capacitor 4150 C1, C2 2 10uF, 6.3V, X5R Chip JMK316BJ106ML (1206) Taiyo Yuden (408) 573- Capacitor 4150 E1E7 7 Testpoint Turret 2501-2 Mill-Max (516) 922- 6000 JP1 1 0.079 Single-Row Header 2802S-03-G1 Comm Con JP1 1 0.079 Center Shunt CCIJ2MM-138G Comm Con R3 1 100k, 1/16W, 1% Chip CR16-1003FM (0603) AAC (800) 528- (Assy. Resistor 1521 A) 1 100k, 1/16W, 1% Chip CR16-1003FM (0603) AAC (800) 528- (Assy. Resistor 1521 B) 1 232k, 1/16W, 1% Chip CR16-2323FM (0603) AAC (800) 528- (Assy. Resistor 1521 C) R1 0 Optional R2 0 (Open) (Assy. A) 0 (Open) (Assy. B)