Datasheet LTC3633A-2, LTC3633A-3 (Analog Devices) - 9

LTC3633A-2/LTC3633A-3
PIN FUNCTIONS (QFN/TSSOP) BOOST2 (Pin 17/Pin 20):
Boosted Floating Driver Supply within the VON1 sense range (0.6V – 6V for LTC3633A-2, for Channel 2. The (+) terminal of the bootstrap capacitor 1.5V – 12V for LTC3633A-3). When VOUT is outside the connects to this pin while the (–) terminal connects to VON sense range, the switching frequency may deviate the SW pin. The normal operation voltage swing of this from the programmed frequency. The pin impedance is pin ranges from a diode voltage drop below INTVCC up nominally 140kΩ. to PVIN+INTVCC.
ITH1 (Pin 26/Pin 1):
Channel 1 Error Amplifier Output and
INTVCC (Pin 18/Pin 21):
Internal 3.3V Regulator Output. Switching Regulator Compensation Pin. Connect this pin The internal power drivers and control circuits are powered to appropriate external components to compensate the from this voltage. The internal regulator is disabled when regulator loop frequency response. Connect this pin to both channel 1 and channel 2 are disabled with the RUN1/ INTVCC to use the default internal compensation. RUN2 inputs. Decouple this pin to power ground with a
TRACKSS1 (Pin 27/Pin 2):
Output Tracking and Soft-Start minimum of 1µF low ESR ceramic capacitor. Input Pin for Channel 1. Forcing a voltage below 0.6V on
BOOST1 (Pin 19/Pin 22):
Boosted Floating Driver Supply this pin bypasses the internal reference input to the error for Channel 1. The (+) terminal of the bootstrap capacitor amplifier. The LTC3633A-2 will servo the FB pin to the connects to this pin while the (–) terminal connects to TRACK voltage. Above 0.6V, the tracking function stops the SW pin. The normal operation voltage swing of this and the internal reference resumes control of the error pin ranges from a diode voltage drop below INTVCC up amplifier. An internal 1.4µA pull up current from INTVCC to PVIN + INTVCC. allows a soft-start function to be implemented by connect-
SV
ing a capacitor between this pin and SGND.
IN (Pin 20/Pin 23):
Signal Input Supply. This pin powers the internal control circuitry. The internal LDO for INTVCC
VFB1 (Pin 28/Pin 3):
Channel 1 Output Feedback Voltage is powered from this pin. Pin. Input to the error amplifier that compares the feedback
PV
voltage to the internal 0.6V reference voltage. Connect this
IN1 (Pins 21, 22/Pins 24, 25):
Power Supply Input for Channel 1. Input voltage to the on chip power MOSFETs pin to a resistor divider network to program the desired on channel 1. output voltage.
SW1 (Pins 23,24/Pins 26, 27):
Channel 1 Switch Node
PGND (Exposed Pad Pin 29/Exposed Pad Pin 29):
Power Connection to External Inductor. Voltage swing of SW is Ground Pin. The (–) terminal of the input bypass capaci- from a diode voltage drop below ground to PV tor, CIN, and the (–) terminal of the output capacitor, COUT, IN. should be tied to this pin with a low impedance connec-
VON1 (Pin 25/Pin 28):
On-Time Voltage Input for Chan- tion. This pin must be soldered to the PCB to provide low nel 1. This pin sets the voltage trip point for the on-time impedance electrical contact to power ground and good comparator. Tying this pin to the regulated output voltage thermal contact to the PCB. makes the on-time proportional to VOUT1 when VOUT1 is 3633a23fb For more information www.linear.com/LTC3633A-2 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