L6920DTR STMicroelectronics

L6920 1V HIGH EFFICIENCY SYNCRONOUS STEP UP CONVERTER Figure 1. Package 1 Features 0.6 TO 5.5V OPERATING INPUT VOLTAGE 1V START UP INPUT VOLTAGE INTERNAL SYNCHRONOUS RECTIFIER TSSOP8 ZERO SHUT DOWN CURRENT 3.3V AND 5V FIXED OR ADJUSTABLE Table 1. Order Codes OUTPUT VOLTAGE (2V UP TO 5.2V) Part Number Package 120m INTERNAL ACTIVE SWITCH L6920D TSSOP8 Tube LOW BATTERY VOLTAGE DETECTION L6920DTR Tape & Reel REVERSE BATTERY PROTECTION 2 Description 1.1 Applications The L6920 is a high efficiency step-up controller re- ONE TO THREE CELL BATTERY DEVICES quiring only three external components to realize the PDA AND HAND HELD INSTRUMENTS conversion from the battery voltage to the selected CELLULAR PHONES - DIGITAL CORDLESS output voltage. PHONE The start up is guaranteed at 1V and the device is op- PAGERS erating down to 0.6V. GPS Internal synchronous rectifier is implemented with a 120m P-channel MOSFET and, in order to improve DIGITAL CAMERAS the efficiency, a variable frequency control is imple- mented. Figure 1. Application Circuit L1 LX OUT V V CC 7 8 OUT 2.5V 3.3V C2 FB 1 500mA SHDN 5 L6920D C3 C1 LBI 2 3 LBO GND REF 4 6 Rev. 2 February 2005 1/13 L6920 Table 1. Pin Description Pin Name Function 1FB Output voltage selector. Connect FB to GND for Vout=5V or to OUT for Vout=3.3V. Connect FB to an external resistor divider for adjustable output voltage (from 2V to 5.2V) see R4 and R5, fig. 7 . 2 LBI Battery low voltage detector input. The internal threshold is set to 1.23V. A resistor divider is needed to adjust the desired low battery threshold: R1 V = 1.23V 1 + -------- see R1 and R2, fig. 7 LBI R2 3 Battery low voltage detector output. If the voltage at the LBI pin drops below the internal LBO threshold typ. 1.23V, LBO goes low. The LBO is an open drain output and so a pull-up resistor (about 200K ) has to be added for correct output setting see R3, fig. 7 . 4 REF 1.23V reference voltage. Bypass this output to GND with a 100nF capacitor for filtering high frequency noise. No capacitor is required for stability 5 Shutdown pin. When pin 5 is below 0.2V the device is in shutdown, when pin 5 is above 0.6V the SHDN device is operating. 6 GND Ground pin 7 LX Step-up inductor connection 8 OUT Power OUTPUT pin Figure 2. Pin Connection (Top view) FB 1 8 OUT LBI 2 7 LX LBO 3 6 GND REF 4 5 SHDN TSSOP8 Table 2. Absolute Maximum Ratings Symbol Parameter Value Unit V V to GND 6 V ccmax cc LBI, SHDN, FB to GND 6 V V Vout to GND 6 V out max Table 3. Thermal Data Symbol Parameter Value Unit R Thermal Resistance Junction to Ambient 250 C/W th j-amb T Maximum Junction Temperature 150 C j 2/13