Datasheet ADP1621 (Analog Devices) - 7

Data Sheet ADP1621 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS SDSN 1 10 IN GND 2 9 CS ADP1621 COMP 3 8 PIN TOP VIEW FB 4 (Not to Scale) 7 GATE
3 -00
FREQ 5 6 PGND
0 09 06 Figure 4. Pin Configuration
Table 4. Pin Function Descriptions Pin No. Mnemonic Description
1 SDSN Shutdown and Synchronization Input. Turn the ADP1621 on by driving SDSN high; turn it off by driving SDSN low. If SDSN is left floating or when the SDSN is pulled low, the ADP1621 goes into shutdown after 50 μs. If synchronization is needed, synchronize the switching frequency to an external clock by connecting the external clock to the SDSN pin. An internal 100 kΩ pull-down resistor is connected from SDSN to GND. 2 GND Ground. 3 COMP Regulation Control Compensation Node. COMP is the output of the internal transconductance error amplifier. Connect a series RC from COMP to GND to compensate the regulator. The nominal voltage range for this pin is 1.0 V to 2.0 V. 4 FB Feedback Input. FB is the input to the internal transconductance error amplifier. Drive FB from the output voltage through a resistive voltage divider. The ratio of the voltage divider sets the output voltage. The regulation voltage at FB is nominally 1.215 V. 5 FREQ Frequency Control Input. Connect a resistor from FREQ to GND to set the free-running switching frequency between 100 kHz and 1.5 MHz. The nominal voltage of this pin is 1.4 V. 6 PGND Power Ground Input. PGND is the ground return for the internal gate driver and the negative input of the internal current-sense amplifier. Connect PGND to GND as close to the ADP1621 as possible. 7 GATE Gate Driver Output. The maximum gate driver output is equal to the PIN voltage. GATE drives the gate of the external n-channel power MOSFET. Connect GATE to the gate of the MOSFET. 8 PIN Power Input. PIN powers the gate driver output. An internal 5.5 V shunt regulator is connected to this pin. Bypass PIN to PGND with a 0.1 μF or greater capacitor. 9 CS Current-Sense Input. CS is the positive input of the current-sense amplifier. When GATE is turned on, the voltage at the CS pin increases linearly from 0 V to a maximum of 116 mV, and the nominal peak slope-compensation output current is 70 μA. When GATE is off, the CS function is disabled. For current sensing in lossless mode, connect CS to the drain of the power MOSFET. The absolute maximum voltage at CS is 33 V. For higher accuracy current sensing or higher switch-node voltages, connect CS to a current-sense power resistor in the source of the power MOSFET. In both sensing methods, it is required to add a slope-compensation resistor, RS, to the CS pin to achieve stability in the inductor current for duty cycles greater than 50%. However, it is recommended to add RS for all duty cycles because load transients can momentarily cause the duty cycle to be greater than 50%, even when the steady- state duty cycle is less than 50%. 10 IN Input Voltage. IN powers the ADP1621 internal circuitry. An internal 5.5 V shunt regulator is connected to this pin. Bypass IN to GND with a 0.1 μF or greater capacitor. Rev. D | Page 7 of 32 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION TYPICAL APPLICATION CIRCUIT TABLE OF CONTENTS REVISION HISTORY SIMPLIFIED BLOCK DIAGRAM SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS THEORY OF OPERATION CONTROL LOOP CURRENT-SENSE CONFIGURATIONS CURRENT LIMIT UNDERVOLTAGE LOCKOUT SHUTDOWN SOFT START INTERNAL SHUNT REGULATORS SETTING THE OSCILLATOR FREQUENCY AND SYNCHRONIZATION FREQUENCY APPLICATION INFORMATION: BOOST CONVERTER ADIsimPower DESIGN TOOL DUTY CYCLE SETTING THE OUTPUT VOLTAGE INDUCTOR CURRENT RIPPLE INDUCTOR SELECTION INPUT CAPACITOR SELECTION OUTPUT CAPACITOR SELECTION DIODE SELECTION MOSFET SELECTION LOOP COMPENSATION SLOPE COMPENSATION CURRENT LIMIT LIGHT LOAD OPERATION Discontinuous Conduction Mode Pulse-Skipping Modulation RECOMMENDED COMPONENT MANUFACTURERS LAYOUT CONSIDERATIONS EFFICIENCY CONSIDERATIONS EXAMPLES OF APPLICATION CIRCUITS STANDARD BOOST CONVERTER—DESIGN EXAMPLE BOOTSTRAPPED BOOST CONVERTER Low Input and High Output Boost Converter High Input Voltage Boost Converter Circuit SEPIC CONVERTER CIRCUIT LOW VOLTAGE POWER-INPUT CIRCUIT LED DRIVER APPLICATION CIRCUITS RELATED DEVICES OUTLINE DIMENSIONS ORDERING GUIDE