LM2773TLEV

User's Guide SNVA310A – June 2008 – Revised April 2013 AN-1769 LM2773 Evaluation Board To operate the LM2773 evaluation board, connect a supply voltage (2.7V-5.5V) to the board connectors Vin and GND. Connecting the EN header's center pin to ON position (VIN) enables the device, and connecting it to OFF position (GND) disables the device. Connecting the Mode (SEL) header's center pin to "+" (Vin) selects the 1.6V output voltage mode and connecting the center pin to "−" (GND) selects the 1.8V output voltage mode. 1 Schematic VOUT: 1.8V or 1.6V VIN = 2.5V to 5.5V VIN CIN 1 µF GND IOUT up to 300 mA VOUT COUT 4.7 µF LM2773 C2+ C1+ C1 1 µF C2 1 µF 2 C2- C1- EN (MODE)SEL Bill of Materials Component Symbol Value Package [U.S. (Metric)] Dimensions (mm) Temperature Characteristic Manufacturer Part # LM2773 -- DSBGA-9 1.511 x 1.511 x 0.6 -- TI LM2773 CIN 1µF, 10V 0402 (1005) 1 x 0.5 x 0.6 X5R TDK C1005X5R1A105K COUT 4.7µF, 6.3V 0603 (1608) 1.6 x 0.8 x 0.8 X5R TDK C1608X5R0J475K C1, C2 1µF, 10V 0402 (1005) 1 x 0.5 x 0.6 X5R TDK C1005X5R1A105K All trademarks are the property of their respective owners. SNVA310A – June 2008 – Revised April 2013 Submit Documentation Feedback AN-1769 LM2773 Evaluation Board Copyright © 2008–2013, Texas Instruments Incorporated 1 LM2773 Evaluation Board Layout 3 www.ti.com LM2773 Evaluation Board Layout Figure 1. Top Layer Figure 2. Bottom Layer (top view, unmirrored) 2 AN-1769 LM2773 Evaluation Board SNVA310A – June 2008 – Revised April 2013 Submit Documentation Feedback Copyright © 2008–2013, Texas Instruments Incorporated Board Operation www.ti.com 4 Board Operation 4.1 Basic Connections To operate the LM2773 evaluation board, connect a supply voltage (2.7V-5.5V) to the board connectors Vin and GND. Connecting the EN header's center pin to ON position (VIN) enables the device, and connecting it to OFF position (GND) disables the device. Connecting the Mode (SEL) header's center pin to "+" (Vin) selects the 1.6V output voltage mode and connecting the center pin to "−" (GND) selects the 1.8V output voltage mode. 4.2 Circuit Description The core of the LM2773 is a two-phase charge pump controlled by an internally generated nonoverlapping clock. The charge pump operates by using external flying capacitors (C1, C2) to transfer charge from the input to the output. At input voltages at or below 3.5V (typ.) for 1.8V mode or 3.3V (typ.) for 1.6V mode, the LM2773 operates in a 1x Gain, with the input current being equal to the load current. At input voltages above 3.5V (typ.) or 3.3V (typ.) for the respective input voltage mode selected, the part utilizes a gain of 2/3x with the input current equal to 2/3 the load current. The two phases of the switched capacitor switching cycle will be referred to as the "charge phase" and the "discharge phase". During the charge phase, flying capacitors are charged by the input supply. After half of the switching cycle [ t = 1/(2×FSW) ], the LM2773 switches to the discharge phase. In this configuration, the charge that was stored on the flying capacitors in the charge phase is transferred to the output. The LM2773 uses fixed frequency pre-regulation to regulate the output voltage to 1.8V or 1.6V (depending on voltage mode selected) during moderate to high load currents. The input and output connections of the flying capacitors are made with internal MOS switches. Pre-regulation limits the gate drive of the MOS switch connected between the voltage input and the flying capacitors. Controlling the on resistance of this switch limits the amount of charge transferred into and out of the flying capacitor during the charge and discharge phases, and in turn helps to keep the output ripple very low. When output currents are low (