LTC3672B-1 PIN FUNCTIONSSW (Pin 1): Switch Node Connection to Inductor. This pin LDO1 (Pin 6): Output of the First Low Dropout Linear connects to the drains of the buck regulator’s main PMOS Regulator. This pin must be bypassed to ground with a and synchronous NMOS switches. 1μF or greater ceramic capacitor. GND (Pin 2): Ground. LDO2 (Pin 7): Output of the Second Low Dropout Linear Regulator. This pin must be bypassed to ground with a ENALL (Pin 3): Enables all three outputs when high, shuts 1μF or greater ceramic capacitor. down the IC when low. This is a MOS gate input. An internal 5.5MΩ resistor pulls this pin to ground. VIN (Pin 8): Input Bias Supply for the IC, and Power Input for the Buck Regulator and LDO2. This pin should BUCKOUT (Pin 4): Output Voltage Sense Connection for be bypassed to ground with a 2.2μF or greater ceramic the Buck Regulator. capacitor. VIN1 (Pin 5): Power Input for the First Low Dropout Linear Exposed Pad (Pin 9): Ground. The Exposed Pad must be Regulator, LDO1. This pin may be connected to the buck soldered to PCB. regulator’s output, VIN, or a voltage not exceeding VIN. BLOCK DIAGRAM 4 8 5 BUCKOUT V V LDO1 IN IN1 6 LDO2 400mA BUCK + 7 SW 1 1M 400k 2M – GND 800k 800k 800k 2 LDO2 LDO1 ENABLE BUCK 2.25MHz OSC 800mV LOGIC REFERENCE ENALL 3 5.5M ENABLE LDO2 ENABLE LDO1 EXPOSED PAD (GND) 9 3672b1 BD 3672B1f 6