LTC3670 PIN FUNCTIONSSW (Pin 1): Buck Regulator Switch Node Connection to In- LDO2_FB (Pin 8): Feedback Voltage Input for the Second ductor. This pin connects to the drains of the buck regulator’s Low Dropout Linear Regulator (LDO2). Typically, an ex- main PMOS and synchronous NMOS switches. ternal resistor divider feeds a fraction of the LDO2 output GND (Pin 2): Ground. voltage to this pin. ENLDO1 (Pin 3): Enables the First Low Dropout Linear LDO1_FB (Pin 9): Feedback Voltage Input for the First Low Regulator (LDO1) When High. This is a MOS gate input. Dropout Linear Regulator (LDO1). Typically, an external There is an internal 4MΩ pull-down. resistor divider feeds a fraction of the LDO1 output volt- age to this pin. ENLDO2 (Pin 4): Enables the Second Low Dropout Linear Regulator (LDO2) When High. This is a MOS gate input. LDO1 (Pin 10): Output of the First Low Dropout Linear There is an internal 4MΩ pull-down. Regulator. This pin must be bypassed to ground with a 1µF or greater ceramic capacitor. ENBUCK (Pin 5): Enables the Buck Converter When High. This is a MOS gate input. There is an internal 4MΩ pull- LDO2 (Pin 11): Output of the Second Low Dropout Linear down. Regulator. This pin must be bypassed to ground with a 1µF or greater ceramic capacitor. BUCKFB (Pin 6): Feedback Voltage Input for the Buck Regulator. Typically, an external resistor divider feeds a VIN (Pin 12): Input Supply. This pin should be bypassed fraction of the buck output voltage to this pin. to ground with a 2.2µF or greater ceramic capacitor. PGOOD (Pin 7): Power Good Open-Drain NMOS Output. Exposed Pad (Pin 13): Ground. This pin must be soldered The PGOOD pin goes Hi-Z when all enabled outputs are to the PCB. within 8% of final value. Rev A 6 For more information www.analog.com Document Outline Features Description Applications Typical Application Absolute Maximum Ratings Pin Configuration Electrical Characteristics Typical Performance Characteristics Pin Functions Block Diagram Operation Typical Application Related Parts