APW7077 Просмотр технического описания (PDF) - Anpec Electronics

Номер в каталоге

Компоненты Описание

производитель

APW7077

PWM Step-Up DC-DC Converter

Anpec Electronics 

APW7077/A

Typical Characteristics (Cont.)

Feedback Voltage vs. Temperature

1.020

1.015

1.010

1.005

1.000

0.995

0.990

0.985

0.980

-40

-20

0

20

40

60

80

Temperature (°C)

Function Description

Operation

The APW7077/A series are low noise fixed frequency

voltage–mode PWM DC–DC controllers, and consist

of start–up circuit, reference voltage, oscillator, loop

compensation network, PWM control circuit, and low

ON resistance driver.

APW7077 provide on–chip feedback resistor and loop

compensation network, the system designer can get

the regulated fixed output voltage 3.3V and 5.0V with

a small number of external components, it is optimized

for battery powered portable products where large

output current is required. APW7077A provide internal

reference voltage 1.0V and output voltage setting by

external resistance for higher voltage requirement. The

quiescent current is typically 120uA (VOUT = 3.3V,

fsw = 300kHz), and can be further reduced to about

1.0uA when the chip is disabled (V < 0.7V).

CE

The APW7077/A operation can be best understood by

referring to the block diagram. The error amplifier

monitors the output voltage via the feedback resistor

divider by comparing the feedback voltage with the

reference voltage. When the feedback voltage is lower

than the reference voltage, the error amplifier output

will decrease. The error amplifier output is then

compared with the oscillator ramp voltage at the PWM

controller.

When the feedback voltage is higher than the reference

voltage, the error amplifier output increases and the

duty cycle decreases. When the external power switch

is on, the current ramps up in the inductor, storing

energy in the magnetic field. When the external power

switch is off, the energy stored in the magnetic field is

transferred to the output filter capacitor and the load.

The output filter capacitor stores the charge while the

Copyright © ANPEC Electronics Corp.

11

Rev. A.4 - Sep, 2005

www.anpec.com.tw

Share Link: