Hitachi 17LD4220, Service Manual

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17” TFT TV Service Manual 21/09/2004
11.2. LM2576
11.2.1. General Description
The LM2576 series of regulators are monolithic integrated circuits ideally suited for easy and convenient
design of a step–down switching regulator (buck converter). All circuits of this series are capable of driving
a 3.0 A load with excellent line and load regulation.
These devices are available in fixed output voltages of 3.3 V, 5.0 V, 12 V, 15 V, and an adjustable output
version. These regulators were designed to minimize the number of external components to simplify the
power supply design. Standard series of inductors optimized for use with the LM2576 are offered by
several different inductor manufacturers.
Since the LM2576 converter is a switch–mode power supply, its efficiency is significantly higher in
comparison with popular three–terminal linear regulators, especially with higher input voltages. In many
cases, the power dissipated is so low that no heatsink is required or its size could be reduced dramatically.
A standard series of inductors optimized for use with the LM2576 are available from several different
manufacturers. This feature greatly simplifies the design of switch–mode power supplies.
The LM2576 features include a guaranteed ±4% tolerance on output voltage within specified input voltages
and output load conditions, and ±10% on the oscillator frequency (±2% over 0°C to 125°C). External
shutdown is included, featuring 80 mA (typical) standby current. The output switch includes cycle–by–cycle
current limiting, as well as
thermal shutdown for full protection under fault conditions.
11.2.2. Features
• 3.3 V, 5.0 V, 12 V, 15 V, and Adjustable Output Versions
• Adjustable Version Output Voltage Range, 1.23 to 37 V ±4% Maximum Over Line and Load Conditions
• Guaranteed 3.0 A Output Current
• Wide Input Voltage Range
• Requires Only 4 External Components
• 52 kHz Fixed Frequency Internal Oscillator
• TTL Shutdown Capability, Low Power Standby Mode
• High Efficiency
• Uses Readily Available Standard Inductors
• Thermal Shutdown and Current Limit Protection
• Moisture Sensitivity Level (MSL) Equals 1
11.2.3. Pin description