Datasheet LTC3458L (Analog Devices) - 8

LTC3458L
W BLOCK DIAGRA
BURST SW VIN 11 1 2 VIN ANTIRING SYNC 3 OSC/SYNC SLOPE UNDER VSELECT – MAX BURST MODE N-DRIVE P-DRIVE R CONTROL T 6 DUTY + MODE V SW1 BEST IZERO IZERO CLOCK DETECT PWM P-DRIVE 12 VOUT AND BURST MODE N-DRIVE P-DRIVE DRIVE LOGIC 4% UNDER UNDERVOLTAGE PGND SLEEP TO ERROR AMPLIFIER/ SLEEP SLEEP BURST COMPARATOR ALL BLOCKS CONTROL BURST ACTIVE MODE – 7 FB I PEAK VIN (DISABLED IN + FIXED I PEAK CURRENT COMP/LIMIT_PEAK BURST MODE) FREQUENCY COMPARATOR MODE BIAS I BURST MODE BURST_PEAK CURRENTS REFERENCE/ I MUX COMP, ILIMIT, I_SENSE BIAS SLOPE IBURST_PEAK, UVLO SLOPE COMP TSD VBEST SOFT-START THERMAL SD SD N-DRIVE SDB TO ALL BLOCKS PGND 9 5 13 10 8 4 3458L BD GND ILIM PGND SS COMP SHDN
U U W U APPLICATIO S I FOR ATIO Detailed Description LTC3458L Programmable Functions
The LTC3458L provides high efficiency, low noise power
Current Limit (ILIMIT)/Peak Burst Current (IBURSTPEAK).
for boost applications with output voltages up to 6V. The The programmable current limit circuit sets the maximum true output disconnect feature eliminates inrush current, peak current in the internal N-channel MOSFET switch. and allows VOUT to go to zero during shutdown. The This clamp level is programmed using a resistor to ground current mode architecture with adaptive slope compensa- on ILIM. In Burst Mode operation, the current limit is tion provides ease of loop compensation with excellent automatically set to ~1/4 of the programmed current limit transient load response. The low RDS(ON), low gate charge for optimal efficiency. An 84.5k RILIM resistor is recom- synchronous switches eliminate the need for an external mended in most applications unless a lower limit is Schottky rectifier, and provide efficient high frequency needed to prevent the external inductor from saturating. pulse width modulation (PWM) control. High efficiency is achieved at light loads when Burst Mode operation is ILIMIT = 180 entered, where the IC’s quiescent current is a low 12μA R typical on VIN. The LTC3458L is designed to provide I is in amps and R is in kΩ. custom performance in a variety of applications with programmable feedback, current limit, oscillator frequency, soft-start, and Burst Mode threshold. I ≈ 1 •I BURSTPEAK LIM 4 3458lfa 8