The ADP1621 is a fixed-frequency, pulse-width modulation (PWM), current-mode, step-up converter controller. It drives an external n-channel MOSFET to convert the input voltage to a higher output voltage. The ADP1621 can also be used to drive flyback, SEPIC, and forward converter topologies, either isolated or nonisolated.

The ADP1621 eliminates the use of a current-sense power resistor by measuring the voltage drop across the on resistance of the n-channel MOSFET. This technique, allowed up to a maximum voltage of 30 V at the switch node, maximizes efficiency and reduces cost. For switch-node voltages higher than 30 V or for more accurate current limiting, the CS pin can be connected to a current-sense resistor in the source of the MOSFET. The slope compensation is implemented by an external resistor, allowing a wide range of external components (inductors and MOSFETs), and can be chosen for various switching frequencies and input and output voltages.

The ADP1621 supply input voltage range is 2.9 V to 5.5 V, although higher input voltages are possible with the use of a small-signal NPN pass transistor or a single resistor. The voltage of the power input can be as low as 1 V for fuel cell applications. The switching frequency is set by an external resistor over a range of 100 kHz to 1.5 MHz and can be synchronized to an external clock by using the SDSN pin. The shutdown quiescent current is less than 10 μA. The ADP1621 has a thermal shutdown feature that shuts down the gate driver when the junction temperature reaches approximately 150°C. The internal soft start circuit limits inrush current at startup. The ADP1621 is available in the 10-lead MSOP lead-free package and is specified over the −40°C to +125°C junction temperature range.

Applications

APD bias

Portable electronic equipment

Isolated dc/dc converter

Step-up/step-down dc/dc converter

LED driver for laptop computer and navigation system

LCD backlighting

Data Sheet, Rev. A, 12/06

Part#	Vin Range	Pwr Stage Vin	Vout Adj Options	Multi-Output	Shutdown Current	Supply Current (max)	Switching Frequency	Iout (max)	Synchronous	Step Down	Step Up	Pkg	Product Description	Price* (1000-4999)
ADP1621	2.9V-5.5V	As Low As 1V	Lossless ISens@<30V Vout, Resistor ISens@>30V	No	10µA	3mA	100 KHz - 1.5 MHz	-	No	No	Yes	MSOP-10	Constant-Frequency, Current-Mode, Step-Up DC/DC Controller	$1.30
ADP1821	3.7V-5.5V	1V-24V	0.6V to 85% PwrStgVin	No	10µA	2mA	300 kHz -600 kHz, Sync up to 1 MHz	20A	Yes	Yes	No	QSOP-16	20 A Step-Down DC-DC Controller	$1.35
ADP1822	3.7V-5.5V	1V-24V	0.6V to 85% PwrStgVin	No	10µA	2mA	300 kHz-600 kHz; Sync up to 1 MHz	20A	Yes	Yes	No	QSOP-24	20 A, PWM, Step-Down DC-DC Controller with Margining and Tracking	$1.40
ADP1823	3.7V-20V	1V-24V	0.6V to 85% PwrStgVin	Yes	20µA	3mA	300 kHz-600 kHz, Sync up to 1 MHz	20A	Yes	Yes	No	LFCSP-32	Versatile Dual, Interleaved Synchronous PWM Buck Controller w/ Tracking	$2.10
ADP1828	3.0V-18V	1V-24V	0.6V to 85% PwrStgVin	No	15µA	3mA	300 kHz to 600 kHz	-	Yes	Yes	No	QSOP-20	Synchronous Buck PWM, Step-Down, DC-to-DC Controller	$1.50
ADP1829	3.0V-18V	1V-24V	0.6V to 85% PwrStgVin	Yes	20µA	3mA	300 kHz-600 kHz, Sync up to 1 MHz	20A	Yes	Yes	-	LFCSP-32	Dual, Interleaved, Step-Down DC-to-DC Controller w/ Tracking	$2.10
ADP1864	3.15V-14V	3.15V-14V	0.8V to Vin	No	15µA	350µA	580 kHz	5A	No	Yes	No	TSOT-6	5A, Constant Frequency, Current-Mode Step-Down DC/DC Controller in TSOT	$1.05

* The pricing listed here is provided only for budgetary purposes as recommended list price in U.S. Dollars in the United States ex factor per unit for the stated volume. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.
** Pricing is currently unavailable. Click on the product number to see the Product Page for additional information.

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• Commercial: 0 to +70 degrees Celsius
• Military : -55 to +125 degrees Celsius
• Industrial: Temperature ranges may vary by model. Please consult the datasheet for more information.
• Automotive: -40 to +125 degrees Celsius

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