PCN20110807

Product Change Notices
PCN No.: 20110807
Date: 8/23/2011
This is to inform you that AME5280 datasheet has been changed from Rev. A.01 to
Rev. B.01. This notification is for your information and concurrence.
If you require data or samples to qualify this change, please contact AME, Inc.
within 30 days of receipt of this notification.
If we do not receive any response from you within 30 calendar days from the
date of this notification, we will consider that you have accepted this PCN.
If you have any questions concerning this change, please contact:
PCN Originator:
Name: Bill Chou
Email: [email protected]
Expected 1st Device Shipment Date: N/A
Earliest Year/Work Week of Changed Product: N/A
Description of Change : Modify absolute maximum ratings:
From:
To:
Reason for Change: To comply AME5280 part real product performance.
QPM018B-B
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Features
n General Description
The AME5280 is a synchronous buck converter with
internal power MOSFETs. It achieves 4A continuous output current over a wide switching frequency range with
excellent load and line regulation.
l 4A Output Current
l 70mΩ Internal Power MOSFET Switch
l Stable with Low ESR Output Ceramic
Capacitors
Current mode operation provides fast transient response
and eases of loop stabilization. Internal soft-start minimizes the inrush supply current at startup. The circuit
protection includes cycle-by-cycle current limiting, output short circuit frequency protection and thermal shutdown. In shutdown mode, the regulator reduces the current less than 10µA of supply current.
l Up to 95% Efficiency
l Less than 10µA Shutdown Current
l Wide Switching Frequency Range from
300KHz ~ 1.4MHz
l Thermal Shutdown
l Cycle-by-Cycle Over Current Protection
l Output Adjustable from 0.8V to V IN
This device is available in SOP-8/PP package with exposed pad for low thermal resistance.
l Short Circuit Frequency Protection
l Available in SOP-8/PP Package
l Green Products Meet RoHS Standards
n Applications
l TV
l Distributed Power Systems
l Pre-Regulator for Linear Regulators
n Typical Operating Circuit
VIN
5V
4.7µH
SW
IN
CIN
10µF
x2
R1
75K
EN
OFF ON
VOUT
3.3V/4A
COUT
22µF
x2
AME5280
FB
COMP
CC2
Optional
CC
1.5nF
RC
20K
GND
R2
24K
FREQ
NC
Rev.B.01
1
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Functional Block Diagram
IN
EN
Current
Sense
UVLO
Enable
5.7A
FREQ
Current
Limit
OSC
SLOPE
SW
COMP
LOGIC
+
0.8V
VREF
+
Soft
Start
EA
GND
PWM
IRCMP
PGND
0.9V
2
SW
OTP
FB
Driver
OVP
Rev. B.01
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Pin Configuration
SOP-8/PP
Top View
7
8
6
AME5280-AZAxxx
5
1. COMP
2. GND
3. EN
AME5280
4. IN
5. SW
1
2
3
6. SW
4
7. FREQ
8. FB
* Die Attach:
Conductive Epoxy
Note:
Connect exposed pad (heat sink on the back) to GND.
n Pin Description
Pin Number
Pin Name
Pin Description
1
COMP
Compensation Node. COMP is used to compensate the regulation control loop.
Connect a series RC network from COMP to GND to compensate the regulation
control loop. In some cases, an additional capacitor from COMP to GND is
required.
2
GND
3
EN
Enable. Internal pull high with a resistor. Pull EN below 0.4V to shut down the
regulator.
4
IN
Power Input. IN supplies the power to the IC, as well as the step-down converter
switches. Bypass IN to GND with a suitable large capacitor to eliminate noise on
the input to the IC.
5, 6
SW
7
FREQ
8
Rev.B.01
FB
Ground. Connect the exposed pad to GND.
Power Switching Output. SW is the switching node that supplies power to the
output. Connect the output LC filter from SW to the output load.
Frequency Adjust Pin. Add a resistor from this pin to ground determines the
switching frequency.
Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB
with a resistive voltage divider from the output voltage. The feedback reference
voltage is 0.8V.
3
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Ordering Information
AME5280 - x x x xxx
Output Voltage
Number of Pins
Package Type
Pin Configuration
Pin Configuration
A
(SOP-8/PP)
4
1. COMP
2. GND
3. EN
4. IN
5. SW
6. SW
7. FREQ
8. FB
Package
Type
Z: SOP/PP
Number of
Pins
A: 8
Output Voltage
ADJ: Adjustable
Rev. B.01
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Available Options
Part Number
Marking*
Output Voltage
Package
Operating Ambient
Temperature Range
AME5280-AZAADJ
A5280
AMyMXX
ADJ
SOP-8/PP
-40oC to +85oC
Note:
1. The first 1 or 2 places represent product code. It is assigned by AME such as AM.
2. y is year code and is the last number of a year. Such as the year code of 2008 is 8.
3. A bar on top of first letter represents Green Part such as A5280.
4. The last 3 places MXX represent Marking Code. It contains M as date code in "month", XX as LN code and
that is for AME internal use only. Please refer to date code rule section for detail information.
5. Please consult AME sales office or authorized Rep./Distributor for the availability of output voltage and package
type.
n Absolute Maximum Ratings
Parameter
Maximum
Unit
Supply Voltage
-0.3V to +6V
V
Switch voltage
-0.7V to +6V
V
-0.3V to VIN +0.3V
V
EN, FB, COMP, FREQ to GND
B*
ESD Classification
Caution: Stress above the listed in absolute maximum ratings may cause permanent damage to the device.
* HBM B: 2000V ~ 3999V
n Recommended Operating Conditions
Parameter
Symbol
Rating
Ambient Temperature Range
TA
-40 to +85
Junction Temperature Range
TJ
-40 to +125
Storage Temperature Range
TSTG
-65 to +150
Rev.B.01
Unit
o
C
5
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Thermal Information
Parameter
Package
Die Attach
Thermal Resistance*
(Junction to Case)
Symbol
Maximum
θ JC
19
Unit
o
C/W
Thermal Resistance
(Junction to Ambient)
SOP-8/PP
Internal Power Dissipation
Conductive Epoxy
θJA
84
PD
1450
mW
Maximum Junction Temperature
150
o
Solder Iron (10Sec)**
350
o
C
C
* Measure θJC on backside center of Exposed Pad.
** MIL-STD-202G 210F
6
Rev. B.01
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Electrical Specifications
TA = 25OC unless otherwise noted.
Parameter
Symbol
Test Condition
Min
Input Voltage Range
3
Input UVLO
2
VEN =5V, VFB=1V
(No Switching)
Quiescent Current
Typ
2.3
Max
Units
5.5
V
2.6
V
µA
460
Shutdown Current
ISHDN
VEN =0V
Feedback Voltage
VFB
0.784
Feedback Current
IFB
-50
0.8
10
µA
0.816
V
50
nA
Load Regulation
0A<IOUT<4A
0.25
%
Line Regulation
3.3V<VIN<6V
0.1
%/V
EN Voltage High
EN Voltage Low
EN Leakage Current
Switching Frequency
Short-Circuit Frequency
1.4
V
VEN
IENLK
FSW
VEN =3V
0.4
V
0.1
1
µA
RFREQ=NC
240
300
360
KHz
RFREQ=120KΩ
480
600
720
KHz
RFREQ=47K Ω
0.8
1
1.2
MHz
RFREQ=30K Ω
1.12
1.4
1.68
MHz
FSWSC
High-side Switch Current Limit
5.3
Low-side Switch Current Limit
0.25
FSW
5.7
A
1
A
Maximum Duty Cycle
100
Minimum Duty Cycle
2.4
Minimum On Time
Error Amp Voltage Gain
AEA
Error Amp Transconductance
GEA
Switch Leakage Current
ISWLK
300
VSW =0V, VEN =0V
%
%
100
ns
600
V/V
400
500
µA/V
0.1
20
µA
High-side Switch On Resistance
RDSON,HI
70
mΩ
Low-side Switch On Resistance
RDSON,LO
70
mΩ
Thermal Shutdown Protection
Rev.B.01
OTP
Rising
170
o
OTH
Hysteresis
20
o
C
C
7
AME
AME5280
n Detailed Description
Normal Operation
The AME5280 uses a user adjustable frequency, current mode step-down architecture with internal MOSFET
switch. During normal operation, the internal high-side
(PMOS) switch is turned on each cycle when the oscillator sets the SR latch, and turned off when the comparator resets the SR latch. The peak inductor current at
which comparator resets the SR latch is controlled by
the output of error amplifier EA. While the high-side switch
is off, the low-side switch turns on until either the inductor current starts to reverse or the beginning of the next
switching cycle.
Dropout Operation
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
Over Temperature Protection
The In most applications the AME5280 does not dissipate much heat due to high efficiency. But, in applications where the AME5280 is running at high ambient temperature with low supply voltage and high duty cycles,
such as in dropout, the heat dissipated may exceed the
maximum junction temperature of the part. If the junction temperature reaches approximately 170oC, the internal high-side power switch will be turned off and the SW
switch will become high impedance.
Short-Circuit Protection
Short-circuit protection will activate once the feedback
voltage falls below 0.3 V, and the operating frequency is
switched to 1/4 of normal switching frequency to reduce
power delivered from input to output.
The output voltage is dropped from the input supply for
the voltage which across the high-side switch. As the
input supply voltage decreases to a value approaching
the output voltage, the duty cycle increases toward the
maximum on-time. Further reduction of the supply voltage forces the high-side switch to remain on for more
than one cycle until it reaches 100% duty cycle.
Over Current Protection
The AME5280 cycle-by-cycle limits the peak inductor
current to protect embedded switch from damage. Hence
the maximum output current (the average of inductor current) is also limited. In case the load increases, the inductor current is also increase. Whenever the current limit
level is reached, the output voltage can not be regulated
and starting to drop.
Soft-Start
The AME5280 employs internal soft-start circuitry to
reduce supply inrush current during startup conditions.
8
Rev. B.01
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Application Information
Inductor Selection
For most applications, the value of the inductor will fall
in the range of 2.2µH to 4.7µH. Its value is chosen based
on the desired ripple current. Large value inductors lower
ripple current and small value inductors result in higher
ripple currents. Higher VIN or VOUT also increase the ripple
current ∆IL:
∆I L =
 V
1
VOUT 1 − OUT
VIN
f ×L





Capacitor Selection
In continuous mode, the source current of the top
MOSFET is a square wave of duty cycle VOUT/VIN. To
prevent large voltage transients, a low ESR input capacitor sized for maximum RMS current must be used. The
maximum RMS capacitor current is given by:
≅ I OMAX
When choosing the input and output ceramic capacitors, choose the X5R or X7R dielectric formulations. These
dielectrics have the best temperature and voltage characteristics of all the ceramics for given value and size.
Output Voltage Programming
The output voltage of the AME5280 is set by a resistive
divider according to the following formula:
A reasonable inductor current ripple is usually set as
1/3 to 1/5 of maximum out current. The DC current rating
of the inductor should be at least equal to the maximum
load current plus half the ripple current to prevent core
saturation. For better efficiency, choose a low DCR inductor.
CIN requires IRMS
For a fixed output voltage, the output ripple is highest
at maximum input voltage since ∆IL increases with input
voltage.
VOUT (V IN − VOUT )
VIN
R1 

V OUT = 0 .8 × 1 +
Volt .
R 2 

Some standard value of R1, R2 for most commonly used
output voltage values are listed in Table 1.
VOUT(V)
R1(KΩ )
R2(KΩ )
1.1
7.5
20
1.2
10
20
1.5
17.4
20
1.8
30
24
2.5
51
24
3.3
75
24
This formula has a maximum at VIN=2VOUT, where
IRMS=IOUT/2. For simplification, use an input capacitor with
a RMS current rating greater than half of the maximum
load current.
The selection of COUT is driven by the required effective
series resistance (ESR). Typically, once the ESR requirement for COUT has been met, the RMS current rating
generally far exceeds the IRIPPLE(P-P) requirement. The
output ripple ∆VOUT is determined by:

1
∆VOUT ≅ ∆I L  ESR +
8 fCOUT

Rev.B.01



9
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
Loop Compensation
The AME5280 employs peak current mode control for
easy use and fast transient response. Peak current mode
control eliminates the double pole effect of the output LC filter. It greatly simplifies the compensation loop design.
With peak current mode control, the buck power stage
can be simplified to be a one-pole and one-zero system
in frequency domain. The pole can be calculated by:
f P1 =
1
2π × C OUT × R L
The zero is a ESR zero due to output capacitor and its
ESR. It can be calculated by:
f Z1 =
1
2π × C OUT × ESRCOUT
Where COUT is the output capacitor, RL is load resistance; ESRCOUT is the equivalent series resistance of
output capacitor.
The compensation design is to shape the converter close
loop transfer function to get desired gain and phase. For
most cases, a series capacitor and resistor network connected to the COMP pin sets the pole-zero and is adequate for a stable high-bandwidth control loop.
In the AME5280, FB pin and COMP pin are the inverting
input and the output of internal transconductance error
amplifier (EA). A series RC and CC compensation network connected to COMP pin provides one pole and one
zero:
for RC<<AEA/GEA,
10
f P2 =
1
GEA
≈

A  2π × CC × AEA
2π × CC ×  RC + EA 
G EA 

fZ2 =
1
2 π × C C × RC
where GEA is the error amplifier transconductance
AEA is the error amplifier voltage gain
RC is the compensation resistor
CC is the compensation capacitor
The desired crossover frequency fC of the system is defined to be the frequency where the control loop has unity
gain. It is also called the bandwidth of the converter. In
general, a higher bandwidth means faster response to
load transient. However, the bandwidth should not be too
high because of system stability concern. When designing the compensation loop, converter stability under
all line and load condition must be considered. Usually,
it is recommended to set the bandwidth to be less than
1/10 of switching frequency. Using selected crossover
frequency, fC, to calculate RC:
RC = f C ×
VOUT 2π × COUT
×
VFB GEA × GCS
where GCS is the current sense circuit transconductance.
The compensation capacitor C C and resistor RC together
make zero. This zero is put somewhere close to the
pole fP1 of selected frequency. CC is selected by:
CC =
COUT × RL
RC
Checking Transient Response
The regulator loop response can be checked by looking
at the load transient response. Switching regulators take
several cycles to respond to a step in load current. When
a load step occurs, VOUT immediately shifts by an amount
equal to (∆ILOAD× ESR), where ESR is the effective series resistance of COUT. ∆ILOAD also begins to charge or
discharge COUT, which generates a feedback error signal.
The regulator loop then acts to return VOUT to its steadystate value. During this recovery time VOUT can be monitored for overshoot or ringing that would indicate a stability problem.
Rev. B.01
AME
AME5280
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
Efficiency Considerations
Although all dissipative elements in the circuit produce
losses, one major source usually account for most of the
losses in AME5280 circuits: I2R losses. The I2R loss
dominates the efficiency loss at medium to high load
currents.
The I2R losses are calculated from the resistances of
the internal switches, RSW , and external inductor RL. In
continuous mode, the average output current flowing
through inductor L is "chopped" between the main switch
and the synchronous switch. Thus the series resistance
looking into the SW pin is a function of both top and
bottom MOSFET RDS(ON) and the duty cycle (D) as follows:
RSW = (RDS(ON)TOP)(D) + (RDS(ON)BOTTOM)(1-D)
The RDS(ON) for both the top and bottom MOSFETs can
be obtained from Electrical Characteristics table. Thus,
to obtained I2R losses, simply add RSW to RL and multiply the result by the square of the average output current.
Other losses including CIN and COUT ESR dissipative
losses and inductor core losses generally account for
less than 2% total additional loss.
Thermal Considerations
In most application the AME5280 does not dissipate
much heat due to its high efficiency. But, in applications
where the AME5280 is running at high ambient temperature with low supply voltage and high duty cycles, such
as in dropout, the heat dissipated may exceed the maximum junction temperature of the part. If the junction
temperature reaches approximately 170oC, both power
switches will be turned off and the SW switch will become high impedance.
Rev.B.01
11
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
Layout Considerations
Connect the FB pin directly to feedback resistors.
The resistor divider must be connected between VOUT and GND.
Rc
Cc
R2
COMP
1
8
FB
R1
GND
2
7
FREQ
GND
EN
3
GND
RFREQ
6
SW
SW
VIN
4
5
L1
SW
VOUT
VIN
D1
COUT
CIN
CIN must be placed between VIN
and GND as closer as possible
SW pad should be connected together to Inductor by wide and
short trace, keep sensitive components away from this trace.
Note:
Connect exposed pad (heat sink on the back) to GND.
12
Rev. B.01
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Characterization Curve
Efficiency vs. Output Current
Load Step
100
Efficiency(%)
90
1
80
VOUT = 3.3V
VOUT = 2.5V
70
VOUT = 1.1V
60
VOUT = 0.8V
50
2
40
VIN = 5.0V
30
0
0.4
0.8
1.2
1.6
2.0
2.4
2.8
3.2
3.6
1mS / div
4.0
Output Current(A)
O
TA = 25 C 500mA~4A
1) VOUT= 200mV/div
2) IOUT = 2A/div
Output Voltage Ripple (Full Load)
Soft Start
1
1
2
2
3
3
1µS / div
1) VIN= 200mV/div
2) VOUT= 5mV/div
3) IOUT = 2A/div
Rev.B.01
400µS / div
1) EN= 1V/div
2) VOUT= 1V/div
3) IOUT = 1A/div
13
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Characterization Curve (Contd.)
VFB vs. Temperature
Frequency vs. Temperature
0.820
330
0.815
325
Frequency(KHZ)
0.810
VFB(V)
0.805
0.800
0.795
0.790
-15
+10
+35
+60
O
+85
+35
+60
+85
+110
Frequency vs. Output Current
350
340
Frequency(KHZ)
Frequency(KHZ)
+10
Frequency vs. Supply Voltage
320
315
310
305
330
320
310
300
290
280
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
5.3
270
0.5
5.5
1.0
1.5
2.0
2.5
3.0
3.5
Supply Voltage(V)
Output Current(A)
Quiescent Current vs. Input Voltage
Quiescent Current vs. Temperature
4.0
480
480
470
Quiescent Current(µA)
470
Quiescent Current (µA)
-15
Temperature(OC)
300
460
450
440
430
420
410
400
390
460
450
440
430
420
410
400
390
380
370
4. 0
4.5
5.0
Input Voltage (V)
14
305
Temperature( C)
325
380
310
295
-40
+110
330
295
3.5
315
300
0.785
0.780
-40
320
5. 5
6. 0
360
-40
-15
+10
+35
+60
+85
+110
Temperature(°C)
Rev. B.01
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Date Code Rule
Month Code
1: January 7: July
2: February 8: August
3: March
9: September
4: April
A: October
5: May
B: November
6: June
C: December
n Tape and Reel Dimension
SOP-8/PP
P
PIN 1
W
AME
AME
Carrier Tape, Number of Components Per Reel and Reel Size
Rev.B.01
Package
Carrier Width (W)
Pitch (P)
Part Per Full Reel
Reel Size
SOP-8/PP
12.0±0.1 mm
4.0±0.1 mm
2500pcs
330±1 mm
15
AME
4A, 300KHz ~ 1.4MHz
Sync Buck Converter
AME5280
n Package Dimension
SOP-8/PP
TOP VIEW
SIDE VIEW
D1
SYMBOLS
θ
E1
E2
E
L1
C
PIN 1
D
e
A1
FRONT VIEW
16
A
A2
b
MILLIMETERS
INCHES
MIN
MAX
MIN
MAX
A
1.350
1.750
0.053
0.069
A1
0.000
0.150
0.000
0.006
A2
1.350
1.600
0.053
0.063
C
0.100
0.250
0.004
0.010
E
3.750
4.150
0.148
0.163
E1
5.700
6.300
0.224
0.248
L1
0.300
1.270
0.012
0.050
b
0.310
0.510
0.012
0.020
D
4.720
5.120
0.186
0.202
1.270 BSC
e
o
0.050 BSC
o
o
8o
θ
E2
2.150
2.513
0.085
0.099
D1
2.150
3.402
0.085
0.134
0
8
0
Rev. B.01
www.ame.com.tw
E-Mail: [email protected]
Life Support Policy:
These products of AME, Inc. are not authorized for use as critical components in life-support
devices or systems, without the express written approval of the president
of AME, Inc.
AME, Inc. reserves the right to make changes in the circuitry and specifications of its devices and
advises its customers to obtain the latest version of relevant information.
 AME, Inc. , August 2011
Document: HU001-DS5280-B.01
Corporate Headquarter
AME, Inc.
2F, 302 Rui-Guang Road, Nei-Hu District
Taipei 114, Taiwan.
Tel: 886 2 2627-8687
Fax: 886 2 2659-2989