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PDF APU3039-HF-3 Data sheet ( Hoja de datos )
| Número de pieza | APU3039-HF-3 | |
| Descripción | Synchronous PWM Controller | |
| Fabricantes | Advanced Power Electronics | |
| Logotipo |  |
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Advanced Power
Electronics Corp.
Technology Licensed from International Rectifier
APU3039-HF-3
Synchronous PWM Controller with Over-Current Protection
Features
Description
Current Limit using Lower MOSFET Sensing
Using the 6V internal regulator for charge pump
circuit allows single supply operation up to 18V
Programmable Switching Frequency up to 400KHz
Soft-Start Function
0.8V Precision Reference Voltage Available
Uncommitted Error Amplifier Available for DDR
Voltage Tracking Applications
Stable with Ceramic Capacitor
RoHS-compliant, halogen-free packages
The APU3039 controller IC is designed to provide a syn-
chronous Buck regulator and is targeted for applications
where cost and size are critical. The APU3039 operates
with a single input supply up to 18V, and the output voltage
can be programmed as low as 0.8V for low voltage
applications. Selectable current limit is provided to
tailor to external MOSFET’s on-resistance for optimum
cost and performance. The APU3039 features an uncom-
mitted error amplifier for tracking output voltage and is
capable of sourcing or sinking current for applications
such as DDR bus termination.
Applications
DDR Memory VDDQ/VTT Applications
Graphic Card
Hard Disk Drive
Netcom on-board DC to DC regulator application
Output voltage as low as 0.8V
Low Cost On-Board DC to DC
This device features a programmable switching frequency
set from 200KHz to 400KHz, under-voltage lockout for
both Vcc and Vc supplies, an external programmable
soft-start function as well as output under-voltage detec-
tion that latches off the device when an output short is
detected.
Typical Application
C3
1uF
C7
0.1uF
C11
Optional
D1
C9
1uF
Vcc VOUT2
SS / SD
U1
Vc
HDrv
APU3039-3 R2
VP
VREF
OCSet
5.76K
Rt LDrv
Comp
C8
5600pF
R1
14K
Gnd
PGnd Fb
C4
1uF
D2
C5
0.1uF
R4
1K
L1
C2 1uH
3x 15uF
25V
Q1
AP9408AGH-3
L2
4.7uH
Q2
AP9412AGH-3
R3
3.16K
Figure 1 - Typical application of APU3039-3
18V
C1
15uF
3.3V @ 8A
C6
2x 330uF
40mΩ
©2009 Advanced Power Electronics Corp. USA
www.a-powerusa.com
200806024-3 1/23
1 page  
Advanced Power
Electronics Corp.
Block Diagram
Vcc 4
0.8V
VREF 1
1.25V
0.2V
Regulator
6V
Bias
Generator
3V
1.25V
3V
22uA
SS / SD 17
POR
VP 20
Fb 19
25K
25K
4V
Vc 0.2V
3.5V
64uA Max
Rt
Oscillator
Ct Enbl
Error Amp
Error Comp
POR
S
Q
R
Reset Dom
Comp 18
OCSet 16
3V
28uA
OC Comp
FbLo Comp
0.4V
POR
APU3039-HF-3
15 VOUT2
12 Rt
10 Vc
9 HDrv
Vcc
6 LDrv
7 PGnd
8 Gnd
Figure 2 - Simplified block diagram of the APU3039-3
©2009 Advanced Power Electronics Corp. USA
www.a-powerusa.com
5/23
5 Page 
Advanced Power
Electronics Corp.
Application Information (cont.)
APU3039-HF-3
Choose AP9408AGH-3 for the control MOSFET and
AP9412AGH-3 for the synchronous MOSFET. These
devices provide low on-resistance in a small TO-252 package.
These values are taken under a certain condition test.
For more details please refer to the AP9408AGH-3 and
AP9412AGH-3 data sheets.
The MOSFETs have the following data:
AP9408AGH-3
VDSS = 30V
ID = 53A
RDS(ON) = 10mΩ
AP9412AGH-3
VDSS = 30V
ID = 68A
RDS(ON) = 6mΩ
The total conduction losses will be:
P = P + PCON(TOTAL)
CON(UPPER)
CON(LOWER)
PCON(TOTAL) = 0.64W
The switching loss is more difficult to calculate, even
though the switching transition is well understood. The
reason is the effect of the parasitic components and
switching times during the switching procedures such
as turn-on / turnoff delays and rise and fall times. The
control MOSFET contributes to the majority of the switch-
ing losses in synchronous Buck converter. The synchro-
nous MOSFET turns on under zero voltage conditions,
therefore, the turn on losses for synchronous MOSFET
can be neglected. With a linear approximation, the total
switching loss can be expressed as:
t tPSW =
VDS(OFF)
2
x
r + f x ILOAD
T
Where:
---(12)
VDS(OFF) = Drain to Source Voltage at off time
tr = Rise Time
tf = Fall Time
T = Switching Period
ILOAD = Load Current
The switching time waveform is shown in Figure 10.
VDS
90%
10%
VGS
td(ON)
tr td(OFF)
tf
Figure 10 - Switching time waveforms.
By using equation (12), we can calculate the total switch-
ing losses.
PSW(TOTAL) = 150mW
Programming the Over-Current Limit
The over-current threshold can be set by connecting a
resistor (RSET) from drain of low side MOSFET to the
OCSet pin. The resistor can be calculated by using equa-
tion (2).
The RDS(ON) has a positive temperature coefficient and it
should be considered for the worse case operation.
RDS(ON) = 8mΩ x 1.5 = 12mΩ
ISET ≅ IO(LIM) = 8A x 1.5 = 12A
(50% over nominal output current)
This results in:
RSET = 5.76kΩ
Feedback Compensation
The APU3039 is a voltage mode controller; the control
loop is a single voltage feedback path including error
amplifier and error comparator. To achieve fast transient
response and accurate output regulation, a compensa-
tion circuit is necessary. The goal of the compensation
network is to provide a closed loop transfer function with
the highest 0dB crossing frequency and adequate phase
margin (greater than 45°).
The output LC filter introduces a double pole, –40dB/
decade gain slope above its corner resonant frequency,
and a total phase lag of 180° (see Figure 11). The reso-
nant frequency of the LC filter is expressed as follows:
1
FLC =
2π x LO x CO
---(13)
Figure 11 shows gain and phase of the LC filter. Since
we already have 180° phase shift just from the output
filter, the system risks being unstable.
Gain Phase
0dB 0
-40dB/decade
From AP9408AGH-3 data sheet we obtain:
AP9408AGH-3
tr = 5ns
tf = 6ns
-180
FLC Frequency
FLC Frequency
Figure 11 - Gain and phase of LC filter.
©2009 Advanced Power Electronics Corp. USA
www.a-powerusa.com
11/23
11 Page | ||
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| PDF Descargar | [ Datasheet APU3039-HF-3.PDF ] | |
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