A8580 Demo Note - 3.3 V OUT , 2.5 A, 425 KHz

Demo Note for the A8580
Evaluation Board
4.0V IN – 40V IN , 3.3V OUT, 2.5A, 425KHz
Asynchronous Buck Regulator with
Low IQ PFM Mode
Page 1 of 13
December 18th, 2012
GENERAL SPECIFICATIONS
Specification
Absolute Maximum Input Voltage
Operating Input Voltage Range
V IN START Threshold, V IN rising
V IN STOP Threshold, V IN falling
Output Voltage (FB: 47K/147K, ±1%)
Steady-State Output Current (12V IN )
Pulse-by-pulse Current Limit @ 30% duty
PWM/PFMn Input
Min
–0.3
4.0
3.6
3.2
3.175
−
3.12
–0.3
Nom
−
12
3.8
3.4
3.302
2.5
3.69
−
Max
40
35
4.0
3.6
3.434
−
4.25
5.5
Units
Volts
Volts
Volts
Volts
Volts
A
A
Volts
OPERATING INSTRUCTIONS
Input Power Connection:
Connect a 12V power supply from V IN to GND that is capable of at least 2.5A. Once
operational, V IN can fall as low as 3.4V TYP (3.6V MAX ) before the A8580 is reset.
PWM/PFMn Input and DIP switch SW1 (SLEEPn):
Connect an external voltage to the PWM/PFMn input and set SW1 (SLEEPn) to control the
A8580’s operating mode. The following table summarizes the A8580’s operating modes based
on SW1 (SLEEPn) and the PWM/PFMn input. Also, PWM/PFMn may be used to synchronize
the A8580 PWM switching frequency by applying a square wave above 510KHz.
SW1
(SLEEPn)
PWM/PFMn
Operating Mode
OFF
(SLEEPn<0.5V)
N/A
Low current SLEEP mode, no output voltage
ON
(SLEEPn>2.1V)
< 0.8V
> 2.6V
CLK signal
Low IQ PFM mode, supports up to 500mA TYP
Normal PWM mode at 425KHz, supports up to 2.5A
Normal PWM mode, synchronized to external CLK
Note: Set SW1 to the “OFF” position before driving the SLEEPn test point by a pulse generator
or an external power supply.
Note: Continuously applying more than 5.5V to the PWM/PFMn pin may damage the A8580.
Output Load Connections:
Connect a load from V OUT to GND. The steady-state load current can be as high as 2.5A. Pulseby-pulse current limit and/or thermal shutdown will occur if the load is greater than 3.7A.
Page 2 of 13
December 18th, 2012
DEMO BOARD PICTURE
PWM/PFMn Input
> 2.6V for PWM
< 0.8V for PFM
SW1
(SLEEPn)
MODIFYING THE DEMO BOARD TO PRODUCE V OUT > 5.5V
If the demo board is modified to produce more than 5.5Vout two changes must be made:
1) Jumper J1 must be set to the “lower” position (shown below) so the on-board 3.3V LDO (U2)
will deliver the BIAS voltage to the A8580.
2) Diode D2 must be rotated 90° clockwise so it is “in circuit” and the 3.3V LDO (U2) will
operate. If U2 is operational, the Low IQ current of the EVB will increase.
Rotate D2 90° so it
connects to this pad
Move J1 to the
“lower” position
Page 3 of 13
December 18th, 2012
DEMO BOARD SCHEMATIC
Default jumper position
BIAS
BIAS
VOUT
3.3V
C53
100nF
16V
0603
C52
Empty J1
16V
0603
5
4
C1
4.7uF
16V
1206
U2
LP2992IM5-3.3
C2
4.7uF
16V
1206
C3
4.7uF
16V
1206
C4
Empty
xxV
16 or 18mm
2
Cx
10nF
D2 B140
SOD123
1
3
O In
Bp En
GND
GND
BEAD1
0 ohms
CB
CIN5
47 or 33uF 4.7uF
50V
50V
8mm
1210
CIN5a
0.47uF
100V
0805
CIN5b
47nF
50V
0603
VIN_FILT
CIN4
4.7uF
50V
1210
CIN3
4.7uF
50V
1210
CIN2
0.47uF
100V
0805
CIN1
47nF
50V
0603
COMP
SS
CP
15pF
0603
RZ
26.1K
CZ
470pF
0603
FSET
CSS
22nF
0603
1
2
5
13
9
3
8
VREG12
RFSET
60.4K
4
6
R4
4.99M
COMP
SS
FSET
VREG
RFB1
147K
10
FB
CO2
22uF
16V
1210
CO3
Empty
16V
1210
CO4
CO4a
0.47uF 47nF
100V 50V
0805
0603
CO5
Empty
16V
1210
CO6
Empty
16V
8mm
CO7
Empty
16V
8mm
CO8
Empty
16V
8mm
BODE
Empty
CFB
RFB2
47K
SW
SLEEP
PWM/PFM
CO1
22uF
16V
1210
16
BOOT
BIAS
SW1
PWM/PFM
GND
GND
VOUT
D1
SS2P4
CBOOT
47nF
0603
CVREG
1uF
0603
SLEEP
VIN_FILT
VIN
VIN
LO
8.2uH
7.6mm x 7.6mm
DR72-8R2-R
A8580_LP
SW SW
SW 15
14
SW
BIAS
VIN
11
VIN
RPU
10K
Rsnub
6.81
NPOR
7
POR
TP4 GND
10pF
0603
Csnub
330pF
0603
TP3 GND
TP1 GND
TP2 GND
R6
10K
0
A8580 Evaluation PCB
12.0Vin / 3.3Vout: RFB1 = 147K, RFB2 = 47K
Note: CB is an optional, bulk, electrolytic capacitor for general supply filtering
DEMO BOARD BILL-OF-MATERIALS
REFERENCE DESIGNATORS
FOOTPRINT
QTY.
MANUFACTURER
N/A
1
Allegro
MicroSystems
eTSSOP-16
1
Allegro
MicroSystems
A8580
SOT23-5
0603
0603
0603
0603
0603
1206
0603
0805
1
1
2
1
1
1
1
1
1
National Semi
LP2992IM5-3.3
Digikey
LP2992IM5-3.3CT-ND
1206
0603
3
1
Capacitor, Electrolytic, 33µF or 47µF, 50V, <0.5Ω,
-40°C to 125°C
Thru Hole
8mm x 11.5mm
1
Nichicon
Nichicon
Nichicon
UBW1H330MPD
UBT1H330MPD
UBT1H470MPD
DigiKey
Mouser
Mouser
UBW1H330MPD-ND
647-UBT1H330MPD
647-UBT1H470MPD
CIN1, CIN5b, CO4a, CBOOT
Capacitor, Ceramic, 47nF, 50V, 10%, X7R, -55°C
to 125°C
0603
4
Murata
GRM188R71H473KA61D
Digikey
490-3287-1-ND
CIN2, CIN5a, CO4
Capacitor, Ceramic, 0.47uF, 100V, 10%, X7R, 55°C to 125°C
0805
3
Murata
GRM21BR72A474KA73L
Digikey
490-3326-1-ND
TDK
C3225X7R1H475K
C3225X7R1H475M
Digikey
445-7726-1-ND
445-7727-1-ND
TDK
C3225X7R1C226K
Digikey
445-3945-2-ND
Digikey
Mouser
SS2P4-M3/84AGICT-ND
625-SS2P4-M3/84A
Digikey
Mouser
Digikey
Mouser
B140HWDICT-ND
621-B140HW-7
283-3644-1-ND
704-DRA74-8R2-R
5010K-ND
DESCRIPTION
PCB
A8580 PCB for eTSSOP16, Rev 0.1
U1
A8580, 2A Buck Regulator
U2
R4
R6, RPU
RFB1
RFB2
RFSET
Rsnub
RZ
BEAD1
Regulator, LDO, 3.3V/250mA
Resistor, 4.99MΩ, 1/10W, 1%
Resistor, 10KΩ, 1/10W, 1%
Resistor, 147KΩ, 1/10W, 1%
Resistor, 47KΩ, 1/10W, 1%
Resistor, 60.4KΩ, 1/10W, 1%
Resistor, 6.81Ω, 1/4W, 1%
Resistor, 26.1KΩ, 1/10W, 1%
Resistor, 0Ω, 0805
C1, C2, C3
C53
Capacitor, Ceramic, 4.7µF, 16V, X7R
Capacitor, Ceramic, 100nF, 25V, X7R
CB
MANUFACTURER P/N
SOURCE
PURCHASE P/N
4pcb.com
CIN3, CIN4, CIN5
Capacitor, Ceramic, 4.7µF, 50V, X7R
1210
3
CFB
CO1, CO2
Csnub
CSS
CVREG
CZ
CP
Capacitor, Ceramic, 10pF, 50V, COG
Capacitor, Ceramic, 22µF, 16V, X7R
Capacitor, Ceramic, 330pF, 50V, X7R
Capacitor, Ceramic, 22nF, 50V, X7R
Capacitor, Ceramic, 1µF, 50V, X7R
Capacitor, Ceramic, 560pF, 50V, X7R
Capacitor, Ceramic, 15pF, 50V, C0G
0603
1210
0603
0603
0603
0603
0603
1
2
1
1
1
1
1
Cx
Capacitor, Ceramic, 10nF, 50V, X7R
0603
1
BODE, C4, C52, CIN4, CO3, CO4,
CO5, CO6, CO7, CO8
Empty
Various
0
D1
Schottky Diode, 40V, 2A
SMP
1
Vishay
SS2P4-M3/84A
D2
Schottky Diode, 40V, 1A, SOD123
SOD123
1
Diodes, Inc
Diodes, Inc
B140HW-7
B140HW-7
7.6mm x 7.6mm
4.35mm thick
1
Cooper Bussmann
DRA74-8R2-R
LO
Inductor, 8.2uH, 3.17ASAT @ 25C, 40mΩ
3.3V, BIAS, COMP, FSET, NPOR,
PWM/PFM, SLEEP, SS, SW, VIN,
VOUT, VREG,
Test Points, Red, 0.063" diameter
0.063"
12
Keystone
5010
Digikey
GND
Test Points, Black, 0.063" diameter
0.063"
5
Keystone
5011
Digikey
5011K-ND
J1
Header, 3-pins, 0.1" spacing (Note: P/N is for a 36pin strip)
1
Sullins
PEC36SAAN
Digikey
S1012E-36-ND
SW1
Rubber Feet
DIP Switch, 1 position
Self stick rubber feet
1
4
C & K Components
3M
SDA01H0SBR
SJ-5303 (CLEAR)
Digikey
Digikey
CKN9490CT-ND
SJ5303-7-ND
Page 4 of 13
SMT
Clear
December 18th, 2012
DEMO BOARD PERFORMANCE
Efficiency vs IOUT (PWM Mode)
95
Efficiency (%)
90
85
80
8Vin
75
12Vin
16Vin
70
0
500
1000
1500
2000
2500
Iout (mA)
Efficiency vs IOUT (PFM Mode)
90
80
70
Efficiency (%)
60
50
40
30
20
10
0
10
100
1000
10000
100000
Iout (µA)
Page 5 of 13
December 18th, 2012
DEMO BOARD PERFORMANCE
Load Regulation vs IOUT
0.00
8Vin
12Vin
Deviation from Vo at 100mA (%)
16Vin
-0.10
-0.20
-0.30
-0.40
0
500
1000
1500
2000
2500
Iout (mA)
Line Regulation vs VIN at 1.0A
0.50
Line Regulation(%)
0.25
0.00
-0.25
-0.50
7
8
9
10
11
12
13
14
15
16
17
18
Vin(V)
Page 6 of 13
December 18th, 2012
DEMO BOARD PERFORMANCE
Bode Plot: 12V IN , 330mA Load: 0dB at 59.7KHz, PM=64.3deg, GM=11.3dB
Bode Plot: 12V IN , 2.5A Load: 0dB at 66.8KHz, PM=60deg, GM=8.6dB
Page 7 of 13
December 18th, 2012
DEMO BOARD PERFORMANCE
Component Temperatures: 12V IN , 3.3V OUT , 500mA Load, T AMB =25°C
No Airflow (still air)
Component Temperatures: 12V IN , 3.3V OUT , 2.5A Load, T AMB =25°C
No Airflow (still air)
Page 8 of 13
December 18th, 2012
DEMO BOARD PERFORMANCE
PWM Startup
12V IN , 2.5A (1.3Ω) load, PWM/PFMn=1
PWM Shutdown
12V IN , 2.5A (1.3Ω) load, PWM/PFMn=1
CH1=V OUT , CH2=COMP, CH3=SS, CH4=SLEEPn
CH1=V OUT , CH2=COMP, CH3=SS, CH4=SLEEPn
PWM Output Voltage Ripple
12V IN , 2.5A (1.3Ω) load, PWM/PFMn=1,
CH1=V OUT
PWM Transient Response
12V IN , 1A load step up/down,
PWM/PFMn=1
CH1=V OUT , CH2=COMP, CH4=IOUT
Page 9 of 13
December 18th, 2012
DEMO BOARD PERFORMANCE
PWM to PFM Transition
12V IN , 470mA (7Ω) load
CH1=V OUT , CH2=COMP, CH3=SW,
CH4=PWM/PFMn
PFM to PWM Transition
12V IN , 470mA (7Ω) load
CH1=V OUT , CH2=COMP, CH3=SW,
CH4=PWM/PFMn
PFM Output Voltage Ripple
12V IN , 1mA (3.3KΩ) load
CH1=V OUT
PFM Output Voltage Ripple
12V IN , 400mA (8Ω) load
CH1=V OUT
Page 10 of 13
December 18th, 2012
DEMO BOARD PERFORMANCE
SW Voltage at 12V IN , 100mA load,
PWM/PFMn=1
CH3=SW
Input Voltage Ripple at 12V IN , 2.5A load,
PWM/PFMn=1
CH1=V IN
Page 11 of 13
SW Voltage at 12V IN , 2.5A load,
PWM/PFMn=1
CH3=SW
Output Shorted, Hiccup Mode Operation,
PWM/PFMn=1
CH1=V OUT , CH2=COMP, CH3=SS, CH4=I L
December 18th, 2012
DEMO PCB LAYOUT
Top Layer and Top Silk
Layer 2 and Top Silk
Page 12 of 13
December 18th, 2012
DEMO PCB LAYOUT
Layer 3 and Top Silk
Bottom Layer and Bottom Silk
Page 13 of 13
December 18th, 2012
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