Datasheet LTC3633A, LTC3633A-1 (Analog Devices) - 9

LTC3633A/LTC3633A-1
PIN FUNCTIONS (QFN/TSSOP) V2P5 (Pin 18/Pin 21):
2.5V Regulator Output. Outputs a
ITH1 (Pin 26/Pin 1):
Channel 1 Error Amplifier Output and regulated 2.5V supply voltage capable of supplying 10mA. Switching Regulator Compensation Pin. Connect this pin Bypass this pin with a minimum of 1µF low ESR ceramic to appropriate external components to compensate the capacitor. Tie this pin to INTVCC when this output is not regulator loop frequency response. Connect this pin to being used in the application. INTVCC to use the default internal compensation.
INTVCC (Pin 19/Pin 22):
Internal 3.3V Regulator Output.
TRACKSS1 (Pin 27/Pin 2):
Output Tracking and Soft-Start The internal power drivers and control circuits are powered Input Pin for Channel 1. Forcing a voltage below 0.6V on from this voltage. The internal regulator is disabled when this pin bypasses the internal reference input to the error both channel 1 and channel 2 are disabled with the RUN1/ amplifier. The LTC3633A will servo the FB pin to the TRACK RUN2 inputs. Decouple this pin to power ground with a voltage. Above 0.6V, the tracking function stops and the minimum of 1µF low ESR ceramic capacitor. internal reference resumes control of the error amplifier.
BOOST1 (Pin 20/Pin 23):
Boosted Floating Driver Supply An internal 1.4µA pull up current from INTVCC allows a for Channel 1. The (+) terminal of the bootstrap capacitor soft-start function to be implemented by connecting a connects to this pin while the (–) terminal connects to capacitor between this pin and SGND. the SW pin. The normal operation voltage swing of this
VFB1 (Pin 28/Pin 3):
Channel 1 Output Feedback Voltage pin ranges from a diode voltage drop below INTVCC up Pin. Input to the error amplifier that compares the feedback to VIN + INTVCC. voltage to the internal 0.6V reference voltage. Connect this
V
pin to a resistor divider network to program the desired
IN1 (Pins 21,22/Pins 24, 25):
Power Supply Input for Channel 1. Input voltage to the on chip power MOSFETs output voltage. on channel 1. The internal LDO for INTVCC is powered off
PGND (Exposed Pad Pin 29/Exposed Pad Pin 29):
Power of this pin. Ground Pin. The (–) terminal of the input bypass capaci-
SW1 (Pins 23,24/Pins 26, 27):
Channel 1 Switch Node tor, CIN, and the (–) terminal of the output capacitor, COUT, Connection to External Inductor. Voltage swing of SW is should be tied to this pin with a low impedance connec- from a diode voltage drop below ground to V tion. This pin must be soldered to the PCB to provide low IN. impedance electrical contact to power ground and good
VON1 (Pin 25/Pin 28):
On-Time Voltage Input for Chan- thermal contact to the PCB. nel 1. This pin sets the voltage trip point for the on-time comparator. Tying this pin to the regulated output voltage makes the on-time proportional to VOUT1 when VOUT1 is within the VON1 sense range (0.6V – 6V for LTC3633A, 1.5V – 12V for LTC3633A-1). When VOUT is outside the VON sense range, the switching frequency may deviate from the programmed frequency. The pin impedance is nominally 140kΩ. 3633a1fb For more information www.linear.com/LTC3633A 9 Document Outline Description Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Operation Applications Information Package Description Typical Application Related Parts