Advanced Power
Electronics Corp.
Technology Licensed from International Rectifier
APU3048
SYNCHRONOUS PWM CONTROLLER
WITH OVER CURRENT PROTECTION
FEATURES
LDO Controller with 40mA drive
Dual Synchronous Controller in 16-Pin Package
with 180
o
out-of-phase operation
Configured as 2-Independent PWM Controller
Flexible, Same or Separate Supply Operation
Operation from 4V to 25V Input
Internal 200KHz Oscillator
Soft-Start controls all outputs
Fixed Frequency Voltage Mode
500mA Peak Output Drive Capability
Programmable Outputs
RoHS Compliant & Halogen Free Product
DESCRIPTION
The APU3048 IC combines a Dual synchronous Buck
controller and a linear regulator controller, providing a cost-
ffective, high performance and flexible solution for multi-
output applications. The Dual synchronous controller is
configured as 2-independent PWM controller. APU3048
provides a separate adjustable output by driving a switch
as a linear regulator. This device features an internal
200KHz oscillator, under-voltage lockout for all input
supplies, an external programmable soft start function as
well as output under-voltage detection that latches off the
device when an output short is detected.
APPLICATIONS
DDR Memory Source Sink Vtt Application
Graphic Card
Hard Disk Drive
Power supplies requiring multiple outputs
TYPICAL APPLICATION
.
Figure 1 - Typical application of APU3048
ORDERING INFORMATION
APU3048X
Package Type
O : TSSOP-16
M : SOP-16
Data and specifications subject to change without notice
1
20130814V5.1
Advanced Power
Electronics Corp.
ABSOLUTE MAXIMUM RATINGS
Vcc Supply Voltage .................................................. 25V
VcH1=VcH2 Supply Voltage ...................................... 30V (not rated for inductive load)
Storage Temperature Range ...................................... -65°C To 150°C
Operating Junction Temperature Range ..................... 0°C To 125°C
APU3048
CAUTION: Stresses above those listed in "Absolute Maximum Ratings" may cause permanent damage to the device.
PACKAGE INFORMATION
.
ELECTRICAL SPECIFICATIONS
Unless otherwise specified, these specifications apply over V
cc
=5V, VcH1=VcH2=12V, T
A
=0 to 70°C. Typical values refer
T
A
=25°C. Low duty cycle pulse testing is used which keeps junction and case temperatures equal to the ambient tempera
Parameter
Reference Voltage
Fb Voltage Initial Accuracy
Fb Voltage Line Regulation
UVLO
UVLO Threshold - Vcc
UVLO Hysteresis - Vcc
UVLO Threshold - Vc
UVLO Hysteresis - Vc
UVLO Threshold - Fb
UVLO Hysteresis - F
B
Supply Current
Vcc Dynamic Supply Current
VcH1 Dynamic Supply Current
VcH2 Dynamic Supply Current
Vcc Static Supply Current
VcH1 Static Supply Current
VcH2 Static Supply Current
Dyn I
CC
Dyn I
C
H1
Dyn I
C
H2
I
CCQ
I
C
H1Q
I
C
H2Q
Freq=200KHz, C
L
=1500pF
Freq=200KHz, CL=1500pF
Freq=200KHz, CL=1500pF
SS=0V
SS=0V
SS=0V
-
-
-
-
-
-
5.0
7
7
3.5
2
2
-
-
-
-
-
-
mA
mA
mA
mA
mA
mA
2
UVLO Fb
Fb Ramping Down
UVLO V
CC
UVLO V
C
Supply Ramping Up
Supply Ramping Up
-
-
-
-
-
-
4.2
0.25
3.5
0.2
0.6
0.1
-
-
-
-
-
-
V
V
V
V
V
V
V
FB
L
REG
5V<Vcc<12V
1.225 1.250
-
0.2
1.275
-
V
%
SYM
TEST CONDITION
MIN
TYP
MAX
UNITS
Advanced Power
Electronics Corp.
ELECTRICAL SPECIFICATIONS(Cont.)
Parameter
Error Amp
Fb Voltage Input Bias Current
Fb Voltage Input Bias Current
Transconductance 1
Transconductance 2
Soft-Start Section
Charge Current
Oscillator Section
Frequency
Ramp Amplitude
Output Drivers
Rise Time
Fall Time
Dead Band Time
Max Duty Cycle
Min Duty Cycle
LDO Controller
Drive Current
Fb Voltage
Input Bias Current
I
LDO
V
FB
LDO
I
LDO(BIAS)
30
1.225
45
1.25
0.5
T
r
T
f
T
DB
T
ON
T
OFF
Fb=1V, Freq=200KHz
Fb=1.5V
CL=1500pF
CL=1500pF
-
-
50
85
0
35
50
150
90
0
F
req
V
RAMP
Note 1
180
-
200
1.25
SS I
B
SS=0V
15
25
I
FB1
I
FB2
gm1
gm2
SS=3V
SS=0V
Note 1
-
-
-
-
-0.1
-64
400
600
SYM
TEST CONDITION
MIN
TYP
APU3048
MAX
-
-
-
-
30
220
-
100
100
250
-
-
-
1.275
2
UNITS
uA
uA
umho
umho
uA
KHz
Vpp
ns
ns
ns
%
%
mA
V
uA
.
-
PIN DESCRIPTIONS
PIN SYMBOL
GND
FB2
FB1
PIN#
1
2
16
PIN DESCRIPITON
Ground pin.
Inverting inputs to the error amplifiers. These pins work as feedback
inputs for each channel, and are connected directly to the output of
the switching regulator via a resistor divider to set the output
voltages.
Comp1
Comp2
VcH2
VcH1
3
4
5
12
Compensation pins for the error amplifiers.
Supply voltage for the high side output drivers. These are
connected to voltages that must be at least 4V higher than their bus
voltages (assuming 5V threshold MOSFET). A minimum of
1mF high frequency capacitor must be connected from these pins
to PGnd pin to provide peak drive current capability.
HDrv2
HDrv1
6
11
Output driver for the high side power MOSFET. Connect a diode,
such as BAT54 or 1N4148, from these pins to ground for the
application when the inductor current goes negative (Source/Sink),
soft-start at no load and for the fast load transient from full load to no
load.
3
Advanced Power
Electronics Corp.
PIN DESCRIPTIONS
PIN SYMBOL
LDrv2
LDrv1
PGnd
Vcc
VOUT3
Fb3
SS
PIN#
7
10
8
9
13
14
15
PIN DESCRIPITON
APU3048
Output driver for the synchronous power MOSFET.
This pin serves as the separate ground for MOSFET’s driver and
Supply voltage for the internal blocks of the IC.
Driver signal for the LDO’s external transistor.
LDO’s feedback pin, connected to a resistor divider to set the output
voltage of LDO.
Soft-Start pin. The converter can be shutdown by pulling this pin below 0.5V.
BLOCK DIAGRAM
.
Figure 2 - Simplified block diagram of the APU3048.
4
Advanced Power
Electronics Corp.
THEORY OF OPERATION
Introduction
The APU3048 is designed for multi-outputs
applications. It includes two synchronous buck
controllers and a linear regulator controller. The two
synchronous controller operates with fixed frequency
voltage mode and is configured as two independent
controllers. The timing of the IC is provided through an
internal oscillator circuit. These are two out of phase
oscillators.
APU3048
The converter can be shutdown by pulling the soft-
start pin below 0.5V. This can be easily done by using an
external small signal transistor. During shutdown the
MOSFET drivers and the LDO controller turn off.
Shutdown
Short-Circuit Protection
The outputs are protected against the short circuit.
The APU3048 protects the circuit for shorted output by
sensing the output voltages. The APU3048 shuts down the
PWM signals and LDO controller, when the output voltages
drops below the set values.
Soft-Start
The APU3048 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 Vcc, VcH1 and
VcH2 rise above their threshold 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 onverter.
As the charging voltage of the external capacitor ramps
up, the PWM signals increase from zero to the point the
feedback loop takes control.
Out of Phase Operation
The APU3048 drives its two output stages 180
o
out of phase. In application with single input voltage,
the out of phase peration reduces the input ripple
current. This results in much smaller RMS current in the
input capacitor and reduction of input capacitors.
Under-Voltage Lockout
The under-voltage lockout circuit assures that the
MOSFET driver outputs and LDO controller remain in the
off state whenever the supply voltages drop below set
parameters. Normal operation resumes once the supply
voltages rise above the set values.
.
APPLICATION INFORMATION
Design Example:
The following example is a typical application for
APU3048in current sharing mode. The schematic is
Figure 9 on page 12.
For Switcher
V
IN1
= 12V
V
OUT1
= 3.3V
I
OUT1
= 4A
V
IN2
= 5V
V
OUT2
= 1.8V
I
OUT2
= 4A
δV
OUT
= 75mV
f
S
= 200KHz
For Linear Regulator
V
IN3
= 3.3V
V
OUT3
= 2.5V
I
OUT3
= 2A
When an external resistor divider is connected to the
output as shown in Figure 3.
PWM Section
Output Voltage Programming
Output voltage is programmed by reference voltage
and external voltage divider. The Fb1 pin is the
inverting input of the error amplifier, which is internally
referenced to 1.25V. The divider is ratioed to provide
1.25V at the Fb1 pin when the output is at its desired
value. The output voltage is defined by using the
following equation:
Figure 3 - Typical application of the APU3048 for
programming the output voltage.
Equation (1) can be rewritten as:
Will result to:
V
OUT1
=3.3V
V
REF
=1.25V
R
8
=1KΩ, R
6
=1.64KΩ
V
OUT2
=1.8V
V
REF
=1.25V
R
15
=1K, R
14
=442Ω
5
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