JAJS782 データシート

JAJS782G june 1999 – march 2023 LM2576 , LM2576HV

PRODUCTION DATA

パッケージ・オプション

デバイスごとのパッケージ図は、PDF版データシートをご参照ください。

メカニカル・データ（パッケージ｜ピン）

NDH|5
NEB|5
KTT|5
KC|5

サーマルパッド・メカニカル・データ

KTT|5
- PPTD277

発注情報

9.1.1.1 Definition of Terms

BUCK REGULATOR

A switching regulator topology in which a higher voltage is converted to a lower voltage. Also known as a step-down switching regulator.

BUCK-BOOST REGULATOR

A switching regulator topology in which a positive voltage is converted to a negative voltage without a transformer.

DUTY CYCLE (D)

Ratio of the output switch on-time to the oscillator period. For buck regulator:

Equation 16.

D = \frac{t_{O N}}{T} = \frac{V_{O U T}}{V_{I N}}

For buck-boost regulator:

Equation 17.

D = \frac{t_{O N}}{T} = \frac{|V_{O U T}|}{{|V_{O U T}| + V}_{I N}}

CATCH DIODE OR CURRENT STEERING DIODE

The diode which provides a return path for the load current when the LM2576 switch is OFF.

EFFICIENCY (η)

The proportion of input power actually delivered to the load.

Equation 18.

η = \frac{P_{O U T}}{P_{I N}} = \frac{P_{O U T}}{{P_{O U T} + P}_{L O S S}}

CAPACITOR EQUIVALENT SERIES RESISTANCE (ESR)

The purely resistive component of a real capacitor impedance (see Figure 9-1). It causes power loss resulting in capacitor heating, which directly affects the capacitor operating lifetime. When used as a switching regulator output filter, higher ESR values result in higher output ripple voltages.

Figure 9-1 Simple Model of a Real Capacitor

Most standard aluminum electrolytic capacitors in the 100 μF–1000 μF range have 0.5Ω to 0.1Ω ESR. Higher-grade capacitors (low-ESR, high-frequency, or low-inductance) in the 100 μF to 1000 μF range generally have ESR of less than 0.15Ω.

EQUIVALENT SERIES INDUCTANCE (ESL)

The pure inductance component of a capacitor (see Figure 9-1). The amount of inductance is determined to a large extent on the capacitor construction. In a buck regulator, this unwanted inductance causes voltage spikes to appear on the output.

OUTPUT RIPPLE VOLTAGE

The AC component of the switching regulator output voltage. It is usually dominated by the output capacitor ESR multiplied by the inductor ripple current (ΔI_IND). The peak-to-peak value of this sawtooth ripple current can be determined by reading Section 8.1.3.

CAPACITOR RIPPLE CURRENT

RMS value of the maximum allowable alternating current at which a capacitor can be operated continuously at a specified temperature.

STANDBY QUIESCENT CURRENT (I_STBY)

Supply current required by the LM2576 when in the standby mode ( ON /OFF pin is driven to TTL-high voltage, thus turning the output switch OFF).

INDUCTOR RIPPLE CURRENT (ΔI_IND)

The peak-to-peak value of the inductor current waveform, typically a sawtooth waveform when the regulator is operating in the continuous mode (vs. discontinuous mode).

CONTINUOUS/DISCONTINUOUS MODE OPERATION

Relates to the inductor current. In the continuous mode, the inductor current is always flowing and never drops to zero, vs. the discontinuous mode, where the inductor current drops to zero for a period of time in the normal switching cycle.

INDUCTOR SATURATION

The condition which exists when an inductor cannot hold any more magnetic flux. When an inductor saturates, the inductor appears less inductive and the resistive component dominates. Inductor current is then limited only by the DC resistance of the wire and the available source current.

OPERATING VOLT MICROSECOND CONSTANT (E•T_op)

The product (in VoIt•μs) of the voltage applied to the inductor and the time the voltage is applied. This E•T_op constant is a measure of the energy handling capability of an inductor and is dependent upon the type of core, the core area, the number of turns, and the duty cycle.