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| LM3668-Q1_15 Datasheet, PDF (13/24 Pages) Texas Instruments – 1A, High-Efficiency Dual-Mode Single-Inductor Buck-Boost DC-DC Converter | |||
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8 Application and Implementation
LM3668-Q1
SNVSA84A â APRIL 2015 â REVISED MAY 2015
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TIâs customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
8.1 Application Information
8.1.1 MODE/SYNC Pin
If the MODE/SYNC pin is set high, the device is set to operate at PWM mode only. If MODE/SYNC pin is set low,
the device is set to automatically transition from PFM to PWM or PWM to PFM depending on the load current.
Do not leave this pin floating. The MODE/SYNC pin can also be driven by an external clock to set the desired
switching frequency between 1.6 MHz to 2.7 MHz.
8.1.2 VSEL Pin
The LM3668-Q1 has built in logic for conveniently setting the output voltage, for example if VVSEL high, the output
is set to 5 V; with VVSEL low the output is set to 4.5 V. It is not recommended to use this function for dynamically
switching between 4.5 V and 5 V or switching at maximum load.
8.2 Typical Application
VIN = 2.7 V 5.5 V
C1
10 µF
VDD
PVIN
VOUT
4.5 V/5 V
2.2 µH
SW1
FB
LM3668-Q1
SW2
SYNC/MODE
EN
VSEL
NC
SGND
PGND
L = 4.5 V
H=5V
C2
22 µF
Figure 11. LM3668-Q1 Typical Application Circuit
8.2.1 Design Requirements
8.2.1.1 Maximum Current
The LM3668-Q1 is designed to operate up to 1 A. For input voltages at 2.7 V, the maximum operating current is
600 mA. In any mode it is recommended to avoid starting up the device at minimum input voltage and maximum
load. Special attention must be taken to avoid operating near thermal shutdown when operating in boost mode at
maximum load (1 A). A simple calculation can be used to determine the power dissipation at the operating
condition; PD-MAX = (TJ-MAX-OP â TA-MAX)/RθJA. The LM3668-Q1 has thermal resistance RθJA = 37°C/W.
Copyright © 2015, Texas Instruments Incorporated
Product Folder Links: LM3668-Q1
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