A8580 Demo Note - 5 V OUT , 2.5 A, 425 KHz

Demo Note for the A8580
Evaluation Board
4.0V IN – 40V IN , 5.0V OUT, 2.5A, 425KHz
Asynchronous Buck Regulator with
Low IQ PFM Mode
Page 1 of 13
January 10th, 2013
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
4.90
−
3.12
–0.3
Nom
−
12
3.8
3.4
5.08
2.5
3.69
−
Max
40
35
4.0
3.6
5.28
−
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
January 10th, 2013
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
January 10th, 2013
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
CB
CIN5
47 or 33uF 4.7uF
50V
50V
8mm
1210
GND
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
8.0pF
0603
RZ
59K
CZ
220pF
0603
FSET
CSS
22nF
0603
RFSET
60.4K
5
13
9
3
8
VREG12
GND
GND
LO
10uH
7.6mm x 7.6mm
DRA74-100-R
A8580_LP
COMP
SS
FSET
VREG
15 SW
14
SW
SW
SW
VOUT
D1
SS2P4
CBOOT
47nF
0603
4
6
CO2
22uF
16V
1210
CO3
22uF
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
RFB1
226K
10
FB
CFB
RFB2
42.2K
SW
SLEEP
PWM/PFM
CO1
22uF
16V
1210
16
BOOT
BIAS
SW1
R4
4.99M
VIN
VIN
CVREG
1uF
0603
SLEEP
VIN_FILT
PWM/PFM
1
2
BIAS
GND
BEAD1
0 ohms
VIN
11
VIN
RPU
10K
TP3 GND
Rsnub
6.81
TP1 GND
NPOR
7
POR
TP4 GND
8.0pF
0603
TP2 GND
Csnub
330pF
0603
R6
10K
0
A8580 Evaluation PCB
12.0Vin / 5.0Vout: RFB1 = 226K, RFB2 = 42.2K
Note: CB is an optional, bulk, electrolytic capacitor for general supply filtering
DEMO BOARD BILL-OF-MATERIALS
REFERENCE DESIGNATORS
DESCRIPTION
FOOTPRINT
QTY.
MANUFACTURER
N/A
1
Allegro
MicroSystems
eTSSOP-16
1
Allegro
MicroSystems
A8580
Regulator, LDO, 3.3V/250mA
SOT23-5
1
National Semi
LP2992IM5-3.3
Digikey
LP2992IM5-3.3CT-ND
R4
R6, RPU
Resistor, 4.99MΩ, 1/10W, 1%
0603
1
Resistor, 10KΩ, 1/10W, 1%
0603
2
RFB1
Resistor, 226KΩ, 1/10W, 1%
0603
1
RFB2
Resistor, 42.2KΩ, 1/10W, 1%
0603
1
RFSET
Resistor, 60.4KΩ, 1/10W, 1%
0603
1
Rsnub
Resistor, 6.81Ω, 1/4W, 1%
Resistor, 59KΩ, 1/10W, 1%
1206
1
RZ
0603
1
BEAD1
Resistor, 0Ω, 0805
0805
1
C1, C2, C3
Capacitor, Ceramic, 4.7µF, 16V, X7R
1206
3
C53
Capacitor, Ceramic, 100nF, 25V, X7R
0603
1
CB
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
0603
4
Murata
GRM188R71H473KA61D
Digikey
490-3287-1-ND
CIN2, CIN5a, CO4
Capacitor, Ceramic, 0.47uF, 100V, 10%, X7R
0805
3
Murata
GRM21BR72A474KA73L
Digikey
490-3326-1-ND
CIN3, CIN4, CIN5
Capacitor, Ceramic, 4.7µF, 50V, X7R
1210
3
TDK
C3225X7R1H475K
C3225X7R1H475M
Digikey
445-7726-1-ND
445-7727-1-ND
CFB, CP
Capacitor, Ceramic, 8.0pF, 50V, COG
0603
2
CO1, CO2, CO3
Capacitor, Ceramic, 22µF, 16V, X7R
1210
3
TDK
C3225X7R1C226K
Digikey
445-3945-2-ND
Csnub
Capacitor, Ceramic, 330pF, 50V, X7R
0603
1
CSS
Capacitor, Ceramic, 22nF, 50V, X7R
0603
1
CVREG
Capacitor, Ceramic, 1µF, 50V, X7R
0603
1
CZ
Capacitor, Ceramic, 220pF, 50V, X7R
0603
1
Cx
Capacitor, Ceramic, 10nF, 50V, X7R
0603
1
BODE, C4, C52, CIN4, CO4, CO5,
CO6, CO7, CO8
Empty
Various
0
D1
Schottky Diode, 40V, 2A
SMP
1
Vishay
SS2P4-M3/84A
Digikey
Mouser
SS2P4-M3/84AGICT-ND
625-SS2P4-M3/84A
D2
Schottky Diode, 40V, 1A, SOD123
SOD123
1
Diodes, Inc
Diodes, Inc
B140HW-7
B140HW-7
Digikey
Mouser
B140HWDICT-ND
621-B140HW-7
283-3623-1-ND
704-DRA74-100-R
5010K-ND
PCB
A8580 PCB for eTSSOP16, Rev 0.1
U1
A8580, 2A Buck Regulator
U2
MANUFACTURER P/N
SOURCE
PURCHASE P/N
4pcb.com
7.6mm x 7.6mm x
4.35mm
1
Cooper Bussman
DRA74-100-R
Digikey
Mouser
5010
Digikey
LO
Inductor, 10uH, 2.97ASAT @ 25C, 43mΩ
3.3V, BIAS, COMP, FSET, NPOR,
PWM/PFM, SLEEP, SS, SW, VIN,
VOUT, VREG,
Test Points, Red, 0.063" diameter
0.063"
12
Keystone
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
DIP Switch, 1 position
SMT
1
C & K Components
SDA01H0SBR
Digikey
CKN9490CT-ND
Rubber Feet
Self stick rubber feet
Clear
4
3M
SJ-5303 (CLEAR)
Digikey
SJ5303-7-ND
Page 4 of 13
January 10th, 2013
DEMO BOARD PERFORMANCE
Efficiency vs IOUT (PWM Mode)
100
95
Efficiency (%)
90
85
80
8Vin
75
12Vin
16Vin
70
0
500
1000
1500
2000
2500
Iout (mA)
Efficiency vs IOUT (PFM Mode)
100
90
80
Efficiency (%)
70
60
50
40
30
20
12Vin
10
0
10
100
1000
10000
100000
Iout (µA)
Page 5 of 13
January 10th, 2013
DEMO BOARD PERFORMANCE
Load Regulation vs IOUT
0.00
8Vin
12Vin
Deviation from Vo at 100mA (%)
16Vin
-0.10
-0.20
-0.30
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
January 10th, 2013
DEMO BOARD PERFORMANCE
Bode Plot: 12Vin, 500mA Load: 0dB at 50.52kHz, PM=59.2deg, GM=13.6dB
Bode Plot: 12Vin, 2.0A Load: 0dB at 54.63kHz, PM=60.1deg, GM=11.2dB
Page 7 of 13
January 10th, 2013
DEMO BOARD PERFORMANCE
Component Temperatures: 12V IN , 5V OUT , 500mA Load, T AMB =25°C
No Airflow (still air)
Component Temperatures: 12V IN , 5V OUT , 2.5A Load, T AMB =25°C
No Airflow (still air)
Page 8 of 13
January 10th, 2013
DEMO BOARD PERFORMANCE
PWM Startup
12V IN , 2.5A (2Ω) load, PWM/PFMn=1
PWM Shutdown
12V IN , 2.5A (2Ω) 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 (2Ω) 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
January 10th, 2013
DEMO BOARD PERFORMANCE
PWM to PFM Transition
12V IN , 500mA (5Ω) load
CH1=V OUT , CH2=COMP, CH3=SW,
CH4=PWM/PFMn
PFM to PWM Transition
12V IN , 500mA (5Ω) load
CH1=V OUT , CH2=COMP, CH3=SW,
CH4=PWM/PFMn
PFM Output Voltage Ripple
12V IN , 1mA (5KΩ) load
CH1=V OUT
PFM Output Voltage Ripple
12V IN , 500mA (5Ω) load
CH1=V OUT
Page 10 of 13
January 10th, 2013
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=IOUT
January 10th, 2013
DEMO PCB LAYOUT
Top Layer and Top Silk
Layer 2 and Top Silk
Page 12 of 13
January 10th, 2013
DEMO PCB LAYOUT
Layer 3 and Top Silk
Bottom Layer and Bottom Silk
Page 13 of 13
January 10th, 2013
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