ap2014 Diodes, Inc., ap2014 Datasheet - Page 10

• Manufacturer Part Number: ap2014
• Description: Synchronous Pwm Controller
• Manufacturer: Diodes, Inc.

Synchronous PWM Controller
Introduction
The AP2014 is a fixed frequency, voltage mode
synchronous controller and consists of a precision
reference voltage, an error amplifier, an internal
oscillator, a PWM comparator, 0.5A peak gate driver,
soft-start
Diagram).
The output voltage of the synchronous converter is
set and controlled by the output of the error amplifier;
this is the amplified error signal from the sensed
output voltage and the reference voltage.
This voltage is compared to a fixed frequency linear
sawtooth ramp and generates fixed frequency
pulses of variable duty-cycle, which drives the two
N-channel external MOSFETs.The timing of the IC
is provided through an internal oscillator circuit
which uses on-chip capacitor to set the oscillation
frequency to 200 KHz (400 KHz for “A” version).
Soft-Start
The AP2014 has a programmable soft-start to
control the output voltage rise and limit the current
surge at the start-up. To ensure correct start-up, the
soft-start sequence initiates when the V
rise above their threshold (3.3V
respectively) and generates the Power On Reset
(POR) signal. Soft-start function operates by
sourcing an internal current to charge an external
capacitor to about 3V. Initially, the soft-start function
clamps the E/A’s output of the PWM converter. As
the charging voltage of the external capacitor ramps
up, the PWM signals increase from zero to the point
the feedback loop takes control.
Anachip Corp
www.anachip.com.tw
Function Descriptions
Marking Information
and
shutdown
AP2014 : 200KHz (OSC)
AP2014A : 400KHz (OSC)
Part No.
Logo
circuits
(see
and 4.2V
C
and V
Block
SOP-8L/PDIP-8L
AP2014 X
YY WW X
(Top View)
8
1
CC
10/12
Short-Circuit Protection
The outputs are protected against the short circuit.
The AP2014 protects the circuit for shorted output
by sensing the output voltage (through the external
resistor divider). The AP2014 shuts down the PWM
signals, when the output voltage drops below 0.6V
(0.4V for AP2014A).
The AP2014 also protects the output from
over-voltaging when the control FET is shorted.
This is done by turning on the sync FET with the
maximum duty cycle.
Under-Voltage Lockout
The under-voltage lockout circuit assures that the
MOSFET driver outputs remain in the off state
whenever the supply voltage drops below set
parameters. Lockout occurs if V
3.3V and 4.2V respectively. Normal operation
resumes once V
IC Quiescent Power Dissipation
Power dissipation for IC controller is a function of
applied voltage, gate driver loads and switching
frequency. The IC's maximum power dissipation
occurs when the IC operating with single 12V supply
voltage (Vcc=12V and Vc 24V) at 400KHz switching
frequency and maximum gate loads.
Page 8 show voltage vs. current, when the
gate drivers loaded with 1500pF capacitors. The IC's
power dissipation results to an excessive
temperature rise. This should be considered when
using AP2014A for such application.
5
4
ID code: internal
Xth week: 01~52
Year: "01" =2001
C
and V
"02" =2002
CC
rise above the set values.
AP2014/A
C
and V
Rev. 1.2 Nov 29, 2005
CC
fall below