LT8620EMSE#TRPBF
FEATURES
Wide Input Voltage Range: 3.4V to 65V
Ultralow Quiescent Current Burst Mode® Operation:
2.5μA IQ Regulating 12VIN to 3.3VOUT
Output Ripple < 10mVP-P
High Efficiency Synchronous Operation:
94% Efficiency at 1A, 12VIN to 5VOUT
92% Efficiency at 1A, 12VIN to 3.3VOUT
Fast 30ns Minimum Switch-On Time
Low Dropout Under All Conditions: 250mV at 1A
Safely Tolerates Inductor Saturation in Overload
Low EMI
Adjustable and Synchronizable: 200kHz to 2.2MHz
Accurate 1V Enable Pin Threshold
Internal Compensation
Output Soft-Start and Tracking
Small Thermally Enhanced 16-Lead MSOP and 24-Lead 3mm × 5mm QFN Packages
APPLICATIONS
Automotive and Industrial Supplies
General Purpose Step-Down
GSM Power Supplies
DESCRIPTION
The LT®8620 is a compact, high efficiency, high speed synchronous monolithic step-down switching regulator that accepts a wide input voltage range up to 65V, and consumesonly 2.5µAofquiescent current. Topandbottom power switches are included with all necessary circuitry to minimize the need for external components. Low ripple Burst Mode operation enables high efficiency down to very low output currents while keeping the output ripple below 10mVP-P. A SYNC pin allows synchronization to an external clock. Internal compensation with peak current mode topology allows the use of small inductors and results in fast transient response and good loop stability. The EN/UV pin has an accurate 1V threshold and can be used to programVIN undervoltage lockout orto shut down the LT8620 reducing the input supply current to 1µA. A capacitor on the TR/SS pin programs the output voltage ramp rate during start-up. The PG flag signals when VOUT iswithin ±9% ofthe programmed output voltage aswell as fault conditions. The LT8620 is available in small 16-Lead MSOP and 3mm× 5mmQFNpackageswith exposed pads for low thermal resistance.
The LT8620 is a monolithic, constant frequency, current mode step-down DC/DC converter. An oscillator, with frequency set using a resistor on the RT pin, turns on the internal top power switch at the beginning of each clock cycle. Current in the inductor then increases until the top switch current comparator trips and turns off the top power switch. The peak inductor current at which the top switch turns off is controlled by the voltage on the internal VC node. The error amplifier servos the VC node by comparing the voltage on the VFB pin with an internal 0.97V reference. When the load current increases it causes a reduction in the feedback voltage relative to the reference leading the error amplifier to raise the VC voltageuntilthe average inductor currentmatches thenew load current. When the top power switch turns off, the synchronous power switch turns on until the next clock cycle begins or inductor current falls to zero. If overload conditions result in more than 3.9A flowing through the bottom switch, the next clock cycle will be delayed until switch current returns to a safe level.
Overview
LT3650is a completemonolithic, mid-power, Li-Ionbattery charger, addressing high input voltage applications with solutions that use a minimum of external components. The IC uses a 1MHz constant-frequency, average current mode step-down architecture.
The LT3650 incorporates a 2A switch that is driven by a bootstrappedsupplytomaximizeefficiencyduringcharging cycles. A wide input range allows the operation to fullcharge from 9V to 32V. A precision threshold shutdown pin allows incorporation of UVLO functionality using a simple resistor divider. The IC can also be put into a low current shutdown mode, in which the input supply bias is reduced to only 15µA.
The LT3650incorporates severaldegreesof charge current control freedom. The overall maximum charge current is set using an external inductor current sense resistor. A maximum charge current programming pin allows dynamic manipulation of the battery charge current. The LT3650 also incorporates a system input supply current limit control feature that servos the battery charge current to accommodate overall system load requirements.
