Datasheet LTC3459 (Analog Devices) - 9
| Manufacturer | Analog Devices |
| Description | 10V Micropower Synchronous Boost Converter in ThinSOT |
| Pages / Page | 12 / 9 — TYPICAL APPLICATIONS. Charging a SuperCap®. 5V from Li-Ion Input. 10V … |
| File Format / Size | PDF / 226 Kb |
| Document Language | English |
TYPICAL APPLICATIONS. Charging a SuperCap®. 5V from Li-Ion Input. 10V from 3.3V or 5V Input
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LTC3459
TYPICAL APPLICATIONS
Very low operating quiescent current and synchronous The LTC3459 is designed to control peak inductor current operation allow for greater than 85% conversion effi ciency when VIN is greater than or less than VOUT. This allows in many applications. Lower output voltages will result in current to be controlled during start-up in a boost applica- lower effi ciencies since the N- and P-channel RDS(ON)s tion, for example, or VOUT to be regulated below VIN when will increase. The switching frequency and output power powered from a fresh battery. Peak current control makes capability of the LTC3459 are also dependant on input and the LTC3459 an ideal candidate for charging a back-up output voltages. source such as a SuperCap. Figure 5 shows an application where the LTC3459 is used to charge a two-farad, 5V Su-
Charging a SuperCap®
perCap from a 3.3V input. A NiCd battery could be charged SuperCaps have become a popular alternative to NiCd by the LTC3459 as well, but that application may require batteries as back-up power sources in portable equip- additional circuitry for proper charge termination. ment. Capacitance values of one farad and higher are When VOUT is less than ~3.5V, the body of the internal achievable in small package sizes with leakage currents synchronous P-channel MOSFET rectifi er is connected to in the low microamps. SuperCaps are typically charged VIN, and the SW pin rises a diode above VIN when current at low currents for several minutes until they reach the is delivered to the load. While effi ciency is compromised required back-up voltage. in this mode of operation, current to the SuperCap is
5V from Li-Ion Input
15μH* 100 VOUT = 5V VIN = 4.2V SW 90 V V IN V OUT IN VOUT 2.5V TO 4.2V 5V 1M 47pF LTC3459 + 80 VIN = 2.5V Li-Ion 1μF 4.7μF OFF ON SHDN FB BATTERY GND 332k 70 EFFICIENCY (%) 3459 TA04a *COILCRAFT DO3314 60 50 0.01 0.1 1 10 100 ILOAD (mA) 3459 TA04b
10V from 3.3V or 5V Input
100 33μH* VOUT = 10V SW 90 V V V IN IN = 5V V OUT IN V 3.3V TO 5V OUT 10V 2M 47pF LTC3459 80 VIN = 3.3V 1μF OFF ON SHDN FB 4.7μF GND 280k 70 EFFICIENCY (%) 3459 TA05a *COILCRAFT DO3314 60 50 0.01 0.1 1 10 100 ILOAD (mA) 3459 TA05b 3459fc 9
TYPICAL APPLICATIONS
Very low operating quiescent current and synchronous The LTC3459 is designed to control peak inductor current operation allow for greater than 85% conversion effi ciency when VIN is greater than or less than VOUT. This allows in many applications. Lower output voltages will result in current to be controlled during start-up in a boost applica- lower effi ciencies since the N- and P-channel RDS(ON)s tion, for example, or VOUT to be regulated below VIN when will increase. The switching frequency and output power powered from a fresh battery. Peak current control makes capability of the LTC3459 are also dependant on input and the LTC3459 an ideal candidate for charging a back-up output voltages. source such as a SuperCap. Figure 5 shows an application where the LTC3459 is used to charge a two-farad, 5V Su-
Charging a SuperCap®
perCap from a 3.3V input. A NiCd battery could be charged SuperCaps have become a popular alternative to NiCd by the LTC3459 as well, but that application may require batteries as back-up power sources in portable equip- additional circuitry for proper charge termination. ment. Capacitance values of one farad and higher are When VOUT is less than ~3.5V, the body of the internal achievable in small package sizes with leakage currents synchronous P-channel MOSFET rectifi er is connected to in the low microamps. SuperCaps are typically charged VIN, and the SW pin rises a diode above VIN when current at low currents for several minutes until they reach the is delivered to the load. While effi ciency is compromised required back-up voltage. in this mode of operation, current to the SuperCap is
5V from Li-Ion Input
15μH* 100 VOUT = 5V VIN = 4.2V SW 90 V V IN V OUT IN VOUT 2.5V TO 4.2V 5V 1M 47pF LTC3459 + 80 VIN = 2.5V Li-Ion 1μF 4.7μF OFF ON SHDN FB BATTERY GND 332k 70 EFFICIENCY (%) 3459 TA04a *COILCRAFT DO3314 60 50 0.01 0.1 1 10 100 ILOAD (mA) 3459 TA04b
10V from 3.3V or 5V Input
100 33μH* VOUT = 10V SW 90 V V V IN IN = 5V V OUT IN V 3.3V TO 5V OUT 10V 2M 47pF LTC3459 80 VIN = 3.3V 1μF OFF ON SHDN FB 4.7μF GND 280k 70 EFFICIENCY (%) 3459 TA05a *COILCRAFT DO3314 60 50 0.01 0.1 1 10 100 ILOAD (mA) 3459 TA05b 3459fc 9
