September 2014 Altera Corporation
DS-1041 Datasheet
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Enpirion® Power Datasheet
ER3105DI 500mA Wide VIN
Synchronous Buck Regulator
The Altera® Enpirion® ER3105DI is a 500mA
Synchronous buck regulator with an input range of 3V to
36V. It provides an easy to use, high efficiency low BOM
count solution for a variety of applications.
The ER3105DI integrates both high-side and low-side
NMOS FET's and features a PFM mode for improved
efficiency at light loads. This feature can be disabled if
forced PWM mode is desired. The part switches at a
default frequency of 500kHz but may also be
programmed using an external resistor from 300kHz to
2MHz. The ER3105DI has the ability to utilize internal or
external compensation. By integrating both NMOS
devices and providing internal configuration options,
minimal external components are required, reducing
BOM count and complexity of design.
With the wide VIN
range and reduced BOM the part
provides an easy to implement design solution for a
variety of applications while giving superior
performance. It provides a very robust design for
industrial, battery, and FPGA power applications.
The part is available in a small Pb free 4mmx3mm DFN
plastic package with an operation temperature range of
-40°C to +125°C
Features
• Wide input voltage range 3V to 36V
• Synchronous Operation for high efficiency
• No compensation required
• Integrated High-side and Low-side NMOS devices
• Selectable PFM or forced PWM mode at light loads
• Internal fixed (500kHz) or adjustable Switching
frequency 300kHz to 2MHz
• Continuous output current up to 500mA
• Internal or external Soft-start
• Minimal external components required
• Power-good and enable functions available.
Applications
•FPGA power
• Digital processor power
• Mixed-signal ASIC power
• Industrial control
• Medical devices
• Portable instrumentation
• Distributed Power supplies
• Cloud Infrastructure
FIGURE 1. TYPICAL APPLICATION FIGURE 2. EFFICIENCY vs LOAD, PFM, VOUT = 3.3V
GND
CBOOT
100nF
CFB
R3
R2
SW
SS
SYNC
BOOT
PVIN
PGND
FSW
COM P
FB
AVI N O
POK
EN
CAVINO
1µF
CVIN
10µF
L1
22µH
CO U T
10µF
1
2
3
4
5
6
9
10
11
12
INTERNAL DEFAULT PARAMETER SELECTION
CO U T
10µF
VOUT
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V VIN = 33V
VIN = 12V
09616 September 3, 2014 Rev B
Page 2
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
Ordering Information
PART NUMBER
(Notes 1, 2, 3)
PART
MARKING
TEMP. RANGE
(°C)
PACKAGE
(Pb-Free)
PKG.
DWG. #
ER3105DI 3105 -40 to +125 12 Ld DFN L12.4x3
EVB-ER3105DI Evaluation Board
NOTES:
1. Add “T” suffix for Tape and Reel.
2. These Altera Enpirion Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach
materials, and 100% matte tin plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb
and Pb-free soldering operations). Altera Enpirion Pb-free products are MSL classified at Pb-free peak reflow temperatures that
meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
09616 September 3, 2014 Rev B
Page 3
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Pin Configuration
ER3105DI
(12 LD 4X3 DFN)
TOP VIEW
Pin Descriptions
PIN NUMBER SYMBOL PIN DESCRIPTION
1 SS The SS pin controls the soft-start ramp time of the output. A single capacitor from the SS pin to ground
determines the output ramp rate. See “Soft Start” on page 16 for soft-start details. If the SS pin is tied
to AVINO, an internal soft-start of 2ms will be used.
2 SYNC Synchronization and light load operational mode selection input. Connect to logic high or AVINO for
PWM mode. Connect to logic low or ground for PFM mode. Logic ground enables the IC to automatically
choose PFM or PWM operation. Connect to an external clock source for synchronization with positive
edge trigger. Sync source must be higher than the programmed IC frequency. There is an internal 5MΩ
pull-down resistor to prevent an undefined logic state if SYNC is left floating.
3 BOOT Floating bootstrap supply pin for the power MOSFET gate driver. The bootstrap capacitor provides the
necessary charge to turn on the internal N-Channel MOSFET. Connect an external 100nF capacitor from
this pin to SW.
4 PVIN The input supply for the power stage of the regulator and the source for the internal linear bias regulator.
Place a minimum of 4.7µF ceramic capacitance from PVIN to GND and close to the IC for decoupling.
5 SW Switch node output. It connects the switching FET’s with the external output inductor.
6 PGND Power ground connection. Connect directly to the system GND plane.
7 EN Regulator enable input. The regulator and bias LDO are held off when the pin is pulled to ground. When
the voltage on this pin rises above 1V, the chip is enabled. Connect this pin to PVIN for automatic start-
up. Do not connect EN pin to AVINO since the LDO is controlled by EN voltage.
8 POK Open drain power-good output that is pulled to ground when the output voltage is below regulation limits
or during the soft-start interval. There is an internal 5MΩ internal pull-up resistor.
9 AVINO Output of the internal 5V linear bias regulator. Decouple to PGND with a 1µF ceramic capacitor at the pin.
10 FB Feedback pin for the regulator. FB is the inverting input to the voltage loop error amplifier. COMP is the
output of the error amplifier. The output voltage is set by an external resistor divider connected to FB. In
addition, the PWM regulator’s power-good and UVLO circuits use FB to monitor the regulator output
voltage.
11 COMP COMP is the output of the error amplifier. When it is tied to AVINO, internal compensation is used. When
only an RC network is connected from COMP to GND, external compensation is used. See “Loop
Compensation Design” on page 21 for more details.
12 FSW Frequency selection pin. Tie to AVINO for 500kHz switching frequency. Connect a resistor to GND for
adjustable frequency from 300kHz to 2MHz.
EPAD GND Signal ground connections. Connect to application board GND plane with at least 5 vias. All voltage levels
are measured with respect to this pin. The EPAD MUST not float.
AVINO
EN
PVIN
FB
SW
BOOT
COMP
1
2
3
4
5
12
11
10
9
8POK
SS FSW
PGND 6GND 7
SYNC
09616 September 3, 2014 Rev B
Page 4
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
Typical Application Schematics
FIGURE 3. INTERNAL DEFAULT PARAMETER SELECTION
FIGURE 4. USER PROGRAMMABLE PARAMETER SELECTION
TABLE 1. EXTERNAL COMPONENT SELECTION
VOUT
(V)
L1
(µH)
COUT
(µF)
R2
(kΩ)
R3
(kΩ)
CFB
(pF)
RFSW
(kΩ)
RCOMP
(kΩ)
CCOMP
(pF)
12 45 10 90.9 4.75 22 115 100 470
5 22 2 x 22 90.9 12.4 100 120 100 470
3.3 22 2 x 22 90.9 20 100 120 100 470
2.5 22 2 x 22 90.9 28.7 100 120 100 470
1.8 22 22 100 50 22 120 50 470
GND
CBOOT
100nF
CFB
R3
R2
SW
SS
SYNC
BOOT
PVIN
PGND
FSW
COMP
FB
AVINO
POK
EN
CAVINO
1µF
CVIN
10µF
L1
22µH
COUT
10µF
1
2
3
4
5
6
9
10
11
12
VOUT
GND
CBOOT
100nF
CFB
R3
R2
CSS
CCOMP
RCOMP
RFSW
SW
SS
SYNC
BOOT
PVIN
PGND
FSW
COMP
FB
AVINO
POK
EN
CVIN
10µF
L1
22µH
COUT
10µF
1
2
3
4
5
6
9
10
11
12
VOUT
CAVINO
1µF
09616 September 3, 2014 Rev B
Page 5
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Absolute Maximum Ratings Thermal Information
VIN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +42V
SW to GND. . . . . . . . . . . . . . . . . . . . . . . -0.3V to VIN+0.3V (DC)
SW to GND. . . . . . . . . . . . . . . . . . . . . . . . . . . . . -2V to 43V (20ns)
EN to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +42V
BOOT to SW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +5.5V
COMP, FSW, POK, SYNC, SS, AVINO to GND -0.3V to +5.9V
FB to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to +2.95V
ESD Rating
Human Body Model (Tested per JESD22-A114) . . . . . . . .3kV
Charged Device Model (Tested per JESD22-C101E) . . 1.5kV
Machine Model (Tested per JESD22-A115) . . . . . . . . . . .200V
Latch Up (Tested per JESD-78A; Class 2, Level A). . . . .100mA
Thermal Resistance θJA (°C/W) θJC (°C/W)
DFN Package (Notes 3, 4) . . . . . 44 5.5
Maximum Junction Temperature (Plastic Package) . . . +150°C
Maximum Storage Temperature Range . . . . . . -65°C to +150°C
Ambient Temperature Range . . . . . . . . . . . . . . -40°C to +125°C
Operating Junction Temperature Range . . . . . -40°C to +125°C
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . —
Recommended Operating Conditions
Temperature. . . . . . . . . . . . . . . . . . . . . . . . . . . . . -40°C to +125°C
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3V to 36V
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely
impact product reliability and result in failures not covered by warranty.
NOTES:
3. θJA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach”
features.
4. For θJC, the “case temp” location is the center of the exposed metal pad on the package underside.
Electrical Specifications TA = -40°C to +125°C, VIN
= 3V to 36V, unless otherwise noted. Typical values are at TA=+25°C.
Boldface limits apply over the junction temperature range, -40°C to +125°C
PARAMETER SYMBOL TEST CONDITIONS
MIN
(Note 7) TYP
MAX
(Note 7) UNITS
SUPPLY VOLTAGE
VIN Voltage Range VIN 336V
VIN Quiescent Supply Current IQVFB = 0.7V, SYNC = 0V, FSW
= AVINO 80 µA
VIN Shutdown Supply Current ISD EN = 0V, VIN=36V (Note 5) 1.8 2.5 µA
AVINO Voltage AVINO IOUT = 0mA 4.8 5.15 5.5 V
VIN = 6V; IOUT = 10mA 4.65 55.35 V
POWER-ON RESET
AVINO POR Threshold Rising Edge 2.75 2.95 V
Falling Edge 2.4 2.6 V
OSCILLATOR
Nominal Switching Frequency FSW FSW = AVINO 440 500 560 kHz
Resistor from FSW to GND = 340kΩ240 300 360 kHz
Resistor from FSW to GND = 32.4kΩ2000 kHz
Minimum Off-Time tOFF VIN = 3V 150 ns
Minimum On-Time tON (Note 8) 90 ns
FSW
Voltage VFSW RFSW = 100kΩ0.39 0.4 0.41 V
Synchronization Frequency SYNC 300 2000 kHz
SYNC Pulse Width 100 ns
ERROR AMPLIFIER
Error Amplifier Transconductance
Gain
gm External Compensation 165 230 295 µA/V
Internal Compensation 50 µA/V
FB Leakage Current VFB = 0.6V 1100 nA
Current Sense Amplifier Gain RT0.54 0.6 0.66 V/A
FB Voltage TA = -40°C to +85°C 0.589 0.599 0.606 V
TA = -40°C to +125°C 0.589 0.599 0.609 V
09616 September 3, 2014 Rev B
Page 6
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
POWER-GOOD
Lower POK Threshold - VFB
Rising
90 94 %
Lower POK Threshold - VFB
Falling
82.5 86 %
Upper POK Threshold - VFB
Rising
116.5 120 %
Upper POK Threshold - VFB
Falling
107 112 %
POK Propagation Delay Percentage of the soft-start time 10 %
POK Low Voltage ISINK
= 3mA, EN = AVINO, VFB = 0V 0.05 0.3 V
TRACKING AND SOFT-START
Soft-Start Charging Current ISS 1.5 22.5 µA
Internal Soft-Start Ramp Time EN/SS = AVINO 1.7 2.4 3.1 ms
FAULT PROTECTION
Thermal Shutdown Temperature TSD Rising Threshold 150 °C
THYS Hysteresis 20 °C
Current Limit Blanking Time tOCON 17 Clock
pulses
Overcurrent and Auto Restart
Period
tOCOFF 8 SS cycle
Positive Peak Current Limit IPLIMIT (Note 6) 0.8 0.9 1A
PFM Peak Current Limit IPK _PFM 0.26 0.3 0.34 A
Zero Cross Threshold 10 mA
Negative Current Limit INLIMIT (Note 6) -0.46 -0.40 -0.34 A
POWER MOSFET
High-side RHDS ISW = 100mA, AVINO = 5V 450 600 mΩ
Low-side RLDS ISW = 100mA, AVINO = 5V 250 330 mΩ
SW Leakage Current EN = SW = 0V 300 nA
SW Rise Time tRISE VIN = 36V 10 ns
EN/SYNC
Input Threshold Falling Edge, Logic Low 0.4 1V
Rising Edge, Logic High 1.2 1.4 V
EN Logic Input Leakage Current EN = 0V/36V -0.5 0.5 µA
SYNC Logic Input Leakage
Current
SYNC = 0V 10 100 nA
SYNC = 5V 1.0 1.3 µA
NOTES:
5. Test Condition: VIN = 36V, FB forced above regulation point (0.6V), no switching, and power MOSFET gate charging current
not included.
6. Established by both current sense amplifier gain test and current sense amplifier output test @ IL = 0A.
7. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established
by characterization and are not production tested.
8. Minimum On-Time required to maintain loop stability.
Electrical Specifications TA = -40°C to +125°C, VIN
= 3V to 36V, unless otherwise noted. Typical values are at TA=+25°C.
Boldface limits apply over the junction temperature range, -40°C to +125°C (Continued)
PARAMETER SYMBOL TEST CONDITIONS
MIN
(Note 7) TYP
MAX
(Note 7) UNITS
09616 September 3, 2014 Rev B
Page 7
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Efficiency Curves
FSW = 800kHz, TA = +25°C
FIGURE 5. EFFICIENCY vs LOAD, PFM, VOUT = 5V FIGURE 6. EFFICIENCY vs LOAD, PWM, VOUT = 5V
FIGURE 7. EFFICIENCY vs LOAD, PFM, VOUT = 3.3V FIGURE 8. EFFICIENCY vs LOAD, PWM, VOUT
= 3.3V
FIGURE 9. EFFICIENCY vs LOAD, PFM, VOUT = 1.8V FIGURE 10. EFFICIENCY vs LOAD, PWM, VOUT
= 1.8V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
V
V
V
V
V
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V VIN = 6V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 6V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V VIN = 33V
VIN = 12V
09616 September 3, 2014 Rev B
Page 8
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
FIGURE 11. VOUT REGULATION vs LOAD, PWM, VOUT = 5V FIGURE 12. VOUT REGULATION vs LOAD, PFM, VOUT = 5V
FIGURE 13. VOUT REGULATION vs LOAD, PWM, VOUT = 3.3V FIGURE 14. VOUT
REGULATION vs LOAD, PFM, VOUT
= 3.3V
FIGURE 15. VOUT REGULATION vs LOAD, PWM, VOUT = 1.8V FIGURE 16. VOUT
REGULATION vs LOAD, PFM, VOUT
= 1.8V
Efficiency Curves
FSW = 800kHz, TA = +25°C (Continued)
5.004
5.006
5.008
5.010
5.012
5.014
5.016
5.018
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 6V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
4.975
4.980
4.985
4.990
4.995
5.000
5.005
5.010
5.015
5.020
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
VIN = 6V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
3.322
3.324
3.326
3.328
3.330
3.332
3.334
3.336
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
3.310
3.315
3.320
3.325
3.330
3.335
3.340
3.345
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 12V
VIN = 15V
VIN = 24V
VIN = 33V
1.769
1.770
1.771
1.772
1.773
1.774
1.775
1.776
1.777
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
1.755
1.760
1.765
1.770
1.775
1.780
1.785
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
VIN = 5V
09616 September 3, 2014 Rev B
Page 9
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Efficiency Curves
FSW = 500kHz, TA = +25°C
FIGURE 17. EFFICIENCY vs LOAD, PFM, VOUT = 5V FIGURE 18. EFFICIENCY vs LOAD, PWM, VOUT = 5V
FIGURE 19. EFFICIENCY vs LOAD, PFM, VOUT = 3.3V FIGURE 20. EFFICIENCY vs LOAD, PWM, VOUT
= 3.3V
FIGURE 21. EFFICIENCY vs LOAD, PFM, VOUT = 1.8V FIGURE 22. EFFICIENCY vs LOAD, PWM, VOUT
= 1.8V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 6V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 6V
VIN = 15V VIN = 24V
VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
50
55
60
65
70
75
80
85
90
95
100
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
09616 September 3, 2014 Rev B
Page 10
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
FIGURE 23. EFFICIENCY vs LOAD, PFM, VOU T = 1.8V FIGURE 24. EFFICIENCY vs LOAD, PFM, VOU T = 3.3V
FIGURE 25. EFFICIENCY vs LOAD, PFM, VOUT = 5V FIGURE 26. VOUT REGULATION vs LOAD, PWM, VOUT = 5V
FIGURE 27. VOUT REGULATION vs LOAD, PFM, VOUT = 5V
Efficiency Curves
FSW = 500kHz, TA = +25°C (Continued)
50
55
60
65
70
75
80
85
90
95
100
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 24V
50
55
60
65
70
75
80
85
90
95
100
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 24V
50
55
60
65
70
75
80
85
90
95
100
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1
OUTPUT LOAD (A)
EFFICIENCY (%)
VIN = 24V
5.006
5.008
5.010
5.012
5.014
5.016
5.018
5.020
5.022
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 6V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
4.970
4.980
4.990
5.000
5.010
5.020
5.030
5.040
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 6V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
09616 September 3, 2014 Rev B
Page 11
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
FIGURE 28. VOUT REGULATION vs LOAD, PWM, VOUT = 3.3V FIGURE 29. VOUT
REGULATION vs LOAD, PFM, VOUT
= 3.3V
FIGURE 30. VOUT REGULATION vs LOAD, PWM, VOUT = 1.8V FIGURE 31. VOUT
REGULATION vs LOAD, PFM, VOUT
= 1.8V
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C.
FIGURE 32. START-UP AT NO LOAD, PFM FIGURE 33. START-UP AT NO LOAD, PWM
Efficiency Curves
FSW = 500kHz, TA = +25°C (Continued)
3.336
3.338
3.340
3.342
3.344
3.346
3.348
3.350
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
3.335
3.340
3.345
3.350
3.355
3.360
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
1.803
1.804
1.805
1.806
1.807
1.808
1.809
1.810
1.811
1.812
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
1.802
1.804
1.806
1.808
1.810
1.812
1.814
1.816
1.818
1.820
0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50
OUTPUT LOAD (A)
OUTPUT VOLTAGE (V)
VIN = 5V
VIN = 15V
VIN = 24V
VIN = 33V
VIN = 12V
SW 20V/DIV
VOUT 2V/DIV
EN 20V/DIV
POK 2V/DIV
5ms/DIV
VOUT 2V/DIV
EN 20V/DIV
POK 2V/DIV
5ms/DIV
SW 20V/DIV
09616 September 3, 2014 Rev B
Page 12
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
FIGURE 34. SHUTDOWN IN NO LOAD, PFM FIGURE 35. SHUTDOWN AT NO LOAD, PWM
FIGURE 36. START-UP AT 500mA, PWM FIGURE 37. SHUTDOWN AT 500mA, PWM
FIGURE 38. START-UP AT 500mA, PFM FIGURE 39. SHUTDOWN AT 500mA, PFM
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
VOUT 2V/DIV
EN 20V/DIV
POK 2V/DIV
500ms/DIV
SW 20V/DIV
VOUT 2V/DIV
EN 20V/DIV
POK 2V/DIV
500ms/DIV
SW 20V/DIV
VOUT
2V/DIV
IL 500mA/DIV
POK 2V/DIV
5ms/DIV
SW 20V/DIV
VOUT
2V/DIV
IL 500mA/DIV
POK 2V/DIV
50µs/DIV
SW 20V/DIV
VOUT
2V/DIV
IL 500mA/DIV
POK 2V/DIV
5ms/DIV
SW 20V/DIV
VOUT
2V/DIV
IL 500mA/DIV
POK 2V/DIV
50µs/DIV
SW 20V/DIV
09616 September 3, 2014 Rev B
Page 13
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
FIGURE 40. JITTER AT NO LOAD, PWM FIGURE 41. JITTER AT 500mA, PWM
FIGURE 42. STEADY STATE AT NO LOAD, PFM FIGURE 43. STEADY STATE AT NO LOAD, PWM
FIGURE 44. STEADY STATE AT 500mA LOAD, PWM FIGURE 45. LIGHT LOAD OPERATION AT 20mA, PFM
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
SW 5V/DIV
50n s/DIV
50ns/DIV
SW 5V/DIV
VOUT
10mV/DIV
IL 200mA/DIV
5ms/DIV
SW 20V/DIV
VOUT
10mV/DIV
IL 100mA/DIV
500ns/DIV
SW 20V/DIV
VOUT 10mV/DIV
IL 500mA/DIV
1µs/DIV
SW 20V/DIV
10µs/DIV
VOUT 50mV/DIV
IL 200mA/DIV
SW 20V/DIV
09616 September 3, 2014 Rev B
Page 14
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
FIGURE 46. LIGHT LOAD OPERATION AT 20mA, PWM FIGURE 47. LOAD TRANSIENT, PFM
FIGURE 48. LOAD TRANSIENT, PWM FIGURE 49. PFM TO PWM TRANSITION
FIGURE 50. OVERCURRENT PROTECTION, PWM FIGURE 51. OVERCURRENT PROTECTION HICCUP, PWM
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
VOUT 10mV/DIV
IL 100mA/DIV
1µs/DIV
SW 20V/DIV
VOUT 100mV/DIV
IL 500mA/DIV
200µs/DIV
VOUT
50mV/DIV
IL 500mA/DIV
200µs/DIV
VOUT 10mV/DIV
IL 1A/DIV
2µs/DIV
SW 20V/DIV
VOUT 2V/DIV
IL 500mA/DIV
POK 2V/DIV
20µs/DIV
SW 20V/DIV
50ms/DIV
VOUT 2V/DIV
IL 1A/DIV
POK 2V/DIV
SW 20V/DIV
09616 September 3, 2014 Rev B
Page 15
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
FIGURE 52. SYNC AT 500mA LOAD, PWM FIGURE 53. NEGATIVE CURRENT LIMIT, PWM
FIGURE 54. NEGATIVE CURRENT LIMIT RECOVERY, PWM FIGURE 55. OVER-TEMPERATURE PROTECTION, PWM
Typical Performance Curves
VIN = 24V, VOUT = 3.3V, FSW = 800kHz, TA = +25°C. (Continued)
SYNC 2V/D IV
200ns/DIV
SW 20V/DIV
VOUT 5V/DIV
IL 0.5A/DIV
POK 2V/DIV
10µs/DIV
SW 20V/DIV
VOUT 5V/DIV
POK 2V/DIV
200µs/DIV
IL 0.5A/DIV
SW 20V/DIV
VOUT 2V/DIV
POK 2V/DIV
500µs/DIV
09616 September 3, 2014 Rev B
Page 16
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
Functional Block Diagram
Functional Description
The ER3105DI combines a synchronous buck PWM controller with integrated power switches. The buck controller
drives internal high-side and low-side N-channel MOSFETs to deliver load current up to 500mA. The buck regulator
can operate from an unregulated DC source, such as a battery, with a voltage ranging from +3V to +36V. An internal
LDO provides bias to the low voltage portions of the IC.
Peak current mode control is utilized to simplify feedback loop compensation and reject input voltage variation. User
selectable internal feedback loop compensation further simplifies design. The ER3105DI switches at a default 500kHz.
The buck regulator is equipped with an internal current sensing circuit and the peak current limit threshold is typically
set at 0.9A.
Power-On Reset
The ER3105DI automatically initializes upon receipt of the input power supply and continually monitors the EN pin
state. If EN is held below its logic rising threshold the IC is held in shutdown and consumes typically 1µA from the
PVIN supply. If EN exceeds its logic rising threshold, the regulator will enable the bias LDO and begin to monitor the
AVINO pin voltage. When the AVINO pin voltage clears its rising POR threshold the controller will initialize the
switching regulator circuits. If AVINO never clears the rising POR threshold, the controller will not allow the
switching regulator to operate. If AVINO falls below its falling POR threshold while the switching regulator is
operating, the switching regulator will be shut down until AVINO returns.
Soft Start
To avoid large in-rush current, VOUT is slowly increased at startup to its final regulated value. Soft-start time is
determined by the SS pin connection. If SS is pulled to AVINO, an internal 2ms timer is selected for soft-start. For other
soft-start times, simply connect a capacitor from SS to GND. In this case, a 2µA current pulls up the SS voltage and the
GATE
DRIVE
AND
DEADTIME
BIAS
LDO
OSCILLATOR
PFM
CURRENT
SET
FAULT
LOGIC
450mV/T Slope
Compensation
(PWM only)
600mV/Amp
Current Sense
PWM/PFM
SELECT LOGIC
EN/SOFT
START
Zero Current
Detection
PWM
PWM
600mV VREF
gm
150k
54pF
Internal
Compensation
s
R
Q
Q
POWER
GOOD
LOGIC
FB
Internal = 50µs
External = 230µs
5M
5M
PGND
SW
BOOT
AVINO
PVI N
EN
FB
FS W
SYNC
COMP
POK
GND
PACKAGE
PADDLE
SS
FB
09616 September 3, 2014 Rev B
Page 17
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
FB pin will follow this ramp until it reaches the 600mV reference level. Soft-start time for this case is described by
Equation 1:
Power-OK
POK is the open-drain output of a window comparator that continuously monitors the buck regulator output voltage
via the FB pin. POK is actively held low when EN is low and during the buck regulator soft-start period. After the soft-
start period completes, POK becomes high impedance provided the FB pin is within the range specified in the
“Electrical Specifications” on page 3. Should FB exit the specified window, POK will be pulled low until FB returns.
Over-temperature faults also force POK low until the fault condition is cleared by an attempt to soft-start. There is an
internal 5MΩ internal pull-up resistor.
PWM Control Scheme
The ER3105DI employs peak current-mode pulse-width modulation (PWM) control for fast transient response and
pulse-by-pulse current limiting, as shown in the “Functional Block Diagram” on page 16. The current loop consists of
the current sensing circuit, slope compensation ramp, PWM comparator, oscillator and latch. Current sense trans-
resistance is typically 600mV/A and slope compensation rate, Se, is typically 450mV/T where T is the switching cycle
period. The control reference for the current loop comes from the error amplifier’s output (VCOMP).
A PWM cycle begins when a clock pulse sets the PWM latch and the upper FET is turned on. Current begins to ramp up
in the upper FET and inductor. This current is sensed (VCSA), converted to a voltage and summed with the slope
compensation signal. This combined signal is compared to VCOMP
and when the signal is equal to VCOMP
, the latch is reset.
Upon latch reset the upper FET is turned off and the lower FET turned on allowing current to ramp down in the inductor.
The lower FET will remain on until the clock initiates another PWM cycle. Figure 56 shows the typical operating
waveforms during the PWM operation. The dotted lines illustrate the sum of the current sense and slope compensation
signal.
Output voltage is regulated as the error amplifier varies VCOMP and thus output inductor current. The error amplifier
is a trans-conductance type and its output (COMP) is terminated with a series RC network to GND. This termination is
internal (150k/54pF) if the COMP pin is tied to AVINO. Additionally, the trans-conductance for COMP = AVINO is
50µs vs 220µs for external RC connection. Its non-inverting input is internally connected to a 600mV reference voltage
and its inverting input is connected to the output voltage via the FB pin and its associated divider network.
Light Load Operation
At light loads, converter efficiency may be improved by enabling variable frequency operation (PFM). Connecting the
SYNC pin to GND will allow the controller to choose such operation automatically when the load current is low.
Figure 57 shows the DCM operation. The IC enters the DCM mode of operation when 8 consecutive cycles of inductor
current crossing zero are detected. This corresponds to a load current equal to 1/2 the peak-to-peak inductor ripple
current and set by the following Equation 2:
Time ms()CnF()
∗0.3=(EQ. 1)
FIGURE 56. PWM OPERATION WAVEFORMS
VCOMP
VCSA
DUTY
CYCLE
IL
VOUT
IOUT
VOUT 1D–()
2LFSW
-----------------------------------
=(EQ. 2)
09616 September 3, 2014 Rev B
Page 18
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
where D = duty cycle, FSW = switching frequency, L = inductor value, IOUT = output loading current, VOUT = output
voltage.
While operating in PFM mode, the regulator controls the output voltage with a simple comparator and pulsed FET
current. A comparator signals the point at which FB is equal to the 600mV reference at which time the regulator begins
providing pulses of current until FB is moved above the 600mV reference by 1%. The current pulses are approximately
300mA and are issued at a frequency equal to the converters programmed PWM operating frequency.
Due to the pulsed current nature of PFM mode, the converter can supply limited current to the load. Should load
current rise beyond the limit, VOUT will begin to decline. A second comparator signals an FB voltage 1% lower than
the 600mV reference and forces the converter to return to PWM operation.
Output Voltage Selection
The regulator output voltage is easily programmed using an external resistor divider to scale VOUT relative to the
internal reference voltage. The scaled voltage is applied to the inverting input of the error amplifier; refer to Figure 57.
The output voltage programming resistor, R3, depends on the value chosen for the feedback resistor, R2, and the
desired output voltage, VOUT
, of the regulator. Equation 3 describes the relationship between VOUT and resistor values.
If the desired output voltage is 0.6V, then R3 is left unpopulated and R2 is 0?.
Protection Features
The ER3105DI is protected from overcurrent, negative overcurrent and over-temperature. The protection circuits
operate automatically.
FIGURE 57. DCM MODE OPERATION WAVEFORMS
OC K
IL
VOUT
0
8 CYCLES
PWM DCM PWM
LOAD CURRENT
PULSE SKIP DCM
R3
R2x0.6V
VOUT 0.6V–
----------------------------------
=(EQ. 3)
R2
R3
0.6V
EA
REFERENCE
+
-
VOUT
FIGURE 58. EXTERNAL RESISTOR DIVIDER
FB
09616 September 3, 2014 Rev B
Page 19
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Overcurrent Protection
During PWM on-time, current through the upper FET is monitored and compared to a nominal 0.9A peak overcurrent
limit. In the event that current reaches the limit, the upper FET will be turned off until the next switching cycle. In this
way, FET peak current is always well limited.
If the overcurrent condition persists for 17 sequential clock cycles, the regulator will begin its hiccup sequence. In this
case, both FETS will be turned off and POK will be pulled low. This condition will be maintained for 8 soft-start
periods after which, the regulator will attempt a normal soft-start.
Should the output fault persist, the regulator will repeat the hiccup sequence indefinitely. There is no danger even if
the output is shorted during soft-start.
If VOUT is shorted very quickly, FB may collapse below 5/8ths of its target value before 17 cycles of overcurrent are
detected. The ER3105DI recognizes this condition and will begin to lower its switching frequency proportional to the
FB pin voltage. This insures that under no circumstance (even with VOUT near 0V) will the inductor current run away.
Negative Current Limit
Should an external source somehow drive current into VOUT
, the controller will attempt to regulate VOUT by reversing its
inductor current to absorb the externally sourced current. In the event that the external source is low impedance, current
may be reversed to unacceptable levels and the controller will initiate its negative current limit protection. Similar to
normal overcurrent, the negative current protection is realized by monitoring the current through the lower FET. When
the valley point of the inductor current reaches negative current limit, the lower FET is turned off and the upper FET is
forced on until current reaches the POSITIVE current limit or an internal clock signal is issued. At this point, the lower
FET is allowed to operate. Should the current again be pulled to the negative limit on the next cycle, the upper FET will
again be forced on and current will be forced to 1/6th of the positive current limit. At this point the controller will turn off
both FET’s and wait for COMP to indicate return to normal operation. During this time, the controller will apply a 100Ω
load from SW to PGND and attempt to discharge the output. Negative current limit is a pulse-by-pulse style operation
and recovery is automatic. Negative current limit protection is disabled in PFM operating mode because reverse current
is not allowed to build due to the diode emulation behavior of the lower FET.
Over-Temperature Protection
Over-temperature protection limits maximum junction temperature in the ER3105DI. When junction temperature (TJ)
exceeds +150°C, both FET’s are turned off and the controller waits for temperature to decrease by approximately 20°C.
During this time POK is pulled low. When temperature is within an acceptable range, the controller will initiate a
normal soft-start sequence. For continuous operation, the +125°C junction temperature rating should not be exceeded.
Boot Undervoltage Protection
If the Boot capacitor voltage falls below 1.8V, the Boot undervoltage protection circuit will turn on the lower FET for
400ns to recharge the capacitor. This operation may arise during long periods of no switching such as PFM no load
situations. In PWM operation near dropout (VIN near VOUT), the regulator may hold the upper FET on for multiple
clock cycles. To prevent the boot capacitor from discharging, the lower FET is forced on for approximately 200ns every
10 clock cycles.
Application Guidelines
Simplifying the Design
While the ER3105DI offers user programmed options for most parameters, the easiest implementation with fewest
components involves selecting internal settings for SS, COMP and FSW. Table 1 on page 4 provides component value
selections for a variety of output voltages and will allow the designer to implement solutions with a minimum of
effort.
Operating Frequency
The ER3105DI operates at a default switching frequency of 500kHz if FSW is tied to AVINO. Tie a resistor from FSW to
GND to program the switching frequency from 300kHz to 2MHz, as shown in Equation 4.
RFSW kΩ[] 108.75kΩ∗t(0.2μs)1μs⁄–= (EQ. 4)
09616 September 3, 2014 Rev B
Page 20
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
Where:
t is the switching period in µs.
Synchronization Control
The frequency of operation can be synchronized up to 2MHz by an external signal applied to the SYNC pin. The rising
edge on the SYNC triggers the rising edge of SW. To properly sync, the external source must be at least 10% greater
than the programmed free running IC frequency.
Output Inductor Selection
The inductor value determines the converter’s ripple current. Choosing an inductor current requires a somewhat
arbitrary choice of ripple current, ΔI. A reasonable starting point is 30% of total load current. The inductor value can
then be calculated using Equation 5:
Increasing the value of inductance reduces the ripple current and thus, the ripple voltage. However, the larger
inductance value may reduce the converter’s response time to a load transient. The inductor current rating should be
such that it will not saturate in overcurrent conditions. For typical ER3105DI applications, inductor values generally
lies in the 10µH to 47µH range. In general, higher VOUT will mean higher inductance.
Buck Regulator Output Capacitor Selection
An output capacitor is required to filter the inductor current. The current mode control loop allows the use of low ESR
ceramic capacitors and thus supports very small circuit implementations on the PC board. Electrolytic and polymer
capacitors may also be used.
While ceramic capacitors offer excellent overall performance and reliability, the actual in-circuit capacitance must be
considered. Ceramic capacitors are rated using large peak-to-peak voltage swings and with no DC bias. In the DC/DC
converter application, these conditions do not reflect reality. As a result, the actual capacitance may be considerably
lower than the advertised value. Consult the manufacturers data sheet to determine the actual in-application
capacitance. Most manufacturers publish capacitance vs DC bias so that this effect can be easily accommodated. The
effects of AC voltage are not frequently published, but an assumption of ~20% further reduction will generally suffice.
The result of these considerations may mean an effective capacitance 50% lower than nominal and this value should be
used in all design calculations. Nonetheless, ceramic capacitors are a very good choice in many applications due to
their reliability and extremely low ESR.
The following equations allow calculation of the required capacitance to meet a desired ripple voltage level.
Additional capacitance may be used.
FIGURE 59. RFSW SELECTION vs FSW
300
200
100
0
500 750 1000 1250 1500 1750 2000
FSW (kHz)
RFSW (kΩ)
L= VIN - VOUT
FSW x DI
VOUT
VIN
x(EQ. 5)
09616 September 3, 2014 Rev B
Page 21
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
For the ceramic capacitors (low ESR):
where ΔI is the inductor’s peak-to-peak ripple current, FSW is the switching frequency and COUT is the output capacitor.
If using electrolytic capacitors then:
Loop Compensation Design
When COMP is not connected to AVINO, the COMP pin is active for external loop compensation. The ER3105DI uses
constant frequency peak current mode control architecture to achieve a fast loop transient response. An accurate
current sensing pilot device in parallel with the upper MOSFET is used for peak current control signal and overcurrent
protection. The inductor is not considered as a state variable since its peak current is constant, and the system becomes
a single order system. It is much easier to design a type II compensator to stabilize the loop than to implement voltage
mode control. Peak current mode control has an inherent input voltage feed-forward function to achieve good line
regulation. Figure 60 shows the small signal model of the synchronous buck regulator.
Figure 61 shows the type II compensator and its transfer function is expressed, as shown in Equation 8:
VOUTripple ΔI
8∗FSW∗COUT
----------------------------------------
=(EQ. 6)
VOUTripple ΔI*ESR=(EQ. 7)
dVin
dIL
in
in
iL
+
1:D
+
L
i
Co
Rc
-Av(S)
d
comp
v
RT
Fm
He(S)
+
Ti
(S)
K
o
v
T
v(S)
I
LP
+
1:D
+
Rc
Ro
-Av(S)
RT
Fm
He(S)
Ti
(S)
K
o
T(S)
^^
V
^^
^
^
^
^
FIGURE 60. SMALL SIGNAL MODEL OF SYNCHRONOUS BUCK REGULATOR
RLP
GAIN (VLOOP (S(fi))
-
+
R6
V
V
Vo
GM
V
C7
-
+
C6
VREF
VFB
Vo
VCOMP
FIGURE 61. TYPE II COMPENSATOR
C3R2
R3
AvS() v
ˆCOMP
v
ˆFB
--------------------GM R3
⋅
C6C7
+()R2R3
+()⋅
-----------------------------------------------------------
1S
ωcz1
------------
+
⎝⎠
⎛⎞
1S
ω
cz2
------------
+
⎝⎠
⎛⎞
S1 S
ωcp1
------------
+
⎝⎠
⎛⎞
1S
ω
cp2
------------
+
⎝⎠
⎛⎞
------------------------------------------------------------
== (EQ. 8)
09616 September 3, 2014 Rev B
Page 22
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
where,
Compensator design goal:
High DC gain
Choose Loop bandwidth fc less than 100kHz
Gain margin: >10dB
Phase margin: >40°
The compensator design procedure is as follows:
The loop gain at crossover frequency of fc has a unity gain. Therefore, the compensator resistance R6 is determined by
Equation 9.
Where GM is the trans-conductance, gm, of the voltage error amplifier in each phase. Compensator capacitor C6 is then
given by Equation 10.
Put one compensator pole at zero frequency to achieve high DC gain, and put another compensator pole at either ESR
zero frequency or half switching frequency, whichever is lower in Equation 10. An optional zero can boost the phase
margin. ω
CZ2 is a zero due to R2 and C3.
Put compensator zero 2 to 5 times fc
Example: VIN
= 12V, VO = 5V, IO = 500mA, fSW = 500kHz, R2= 90.9kΩ, Co= 22µF/5m?, L = 39µH, fc = 50kHz, then
compensator resistance R6:
It is acceptable to use 150kΩ as the closest standard value for R6.
It is also acceptable to use the closest standard values for C6 and C7. There is approximately 3pF parasitic capacitance from
VCOMP to GND; Therefore, C7 is optional. Use C6 = 1500pF and C7 = OPEN.
ω
cz1 1
R6C6
---------------ωcz2 1
R2C3
---------------
=ω
cp1
,C6C7
+
R6C6C7
-----------------------ω
cp2
R2R3
+
C3R2R3
-----------------------
=,=,=
R6
2πfcVoCoRt
GM VFB
⋅
--------------------------------- 27.3 3
×10 fcVoCo
⋅== (EQ. 9)
C6
RoCo
R6
---------------VoCo
IoR6
---------------C7max RcCo
R6
---------------1
πfSWR6
----------------------(, )=,== (EQ. 10)
C31
πfcR2
----------------
=(EQ. 11)
R627.3 3
×10 50kHz 5V 22μF⋅⋅⋅ 150.2kΩ==
(EQ. 12)
C65V 22⋅μF
500mA 150kΩ⋅
---------------------------------------------1.46nF== (EQ. 13)
C7max 5mΩ22 μF⋅
150kΩ
---------------------------------- 1
π500kHz 150kΩ⋅⋅
---------------------------------------------------------(, )0.7pF 4.2pF(,)== (EQ. 14)
09616 September 3, 2014 Rev B
Page 23
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Use C3 = 68pF. Note that C3 may increase the loop bandwidth from previous estimated value. Figure 62 shows the
simulated voltage loop gain. It is shown that it has a 75kHz loop bandwidth with a 61° phase margin and 6dB gain
margin. It may be more desirable to achieve an increased gain margin. This can be accomplished by lowering R6 by
20% to 30%. In practice, ceramic capacitors have significant derating on voltage and temperature, depending on the
type. Please refer to the ceramic capacitor datasheet for more details.
Layout Considerations
Proper layout of the power converter will minimize EMI and noise and insure first pass success of the design. PCB
layouts are available from Altera. In addition, Figure 63 will make clear the important points in PCB layout. In reality,
PCB layout of the ER3105DI is quite simple.
A multi-layer printed circuit board with GND plane is recommended. Figure 63 shows the connections of the critical
components in the converter. Note that capacitors CIN and COUT could each represent multiple physical capacitors. The
most critical connections are to tie the PGND pin to the package GND pad and then use vias to directly connect the
GND pad to the system GND plane. This connection of the GND pad to system plane insures a low impedance path
for all return current, as well as an excellent thermal path to dissipate heat. With this connection made, place the high
frequency MLCC input capacitor near the PVIN pin and use vias directly at the capacitor pad to tie the capacitor to the
system GND plane.
The boot capacitor is easily placed on the PCB side opposite the controller IC and 2 vias directly connect the capacitor
to BOOT and SW.
Place a 1µF MLCC near the AVINO pin and directly connect its return with a via to the system GND plane.
C31
π50kHz 90.9kΩ⋅⋅
-------------------------------------------------------
=70pF=(EQ. 15)
FIGURE 62. SIMULATED LOOP GAIN
60
45
30
15
0
-15
-30
100 1k 10k 100k 1M
FREQUENCY (Hz)
180
150
120
90
60
30
0
100 1k 10k 100k 1M
FREQUENCY (Hz)
PHASE (°)GAIN (dB)
09616 September 3, 2014 Rev B
Page 24
ER3105DI 500mA Wide VIN Synchronous Buck Regulator September 2014 Altera Corporation
Place the feedback divider close to the FB pin and do not route any feedback components near SW or BOOT. If external
components are used for SS, COMP or FSW the same advice applies.
Document Revision History
The table lists the revision history for this document.
Date Version Changes
September 2014 1.1 Corrected y-axis label on Figures 17--22 inclusive.
March 2014 1.0 Initial release.
FIGURE 63. PRINTED CIRCUIT BOARD POWER PLANES AND ISLANDS
RFSW
C A V I N O
09616 September 3, 2014 Rev B
Page 25
ER3105DI 500mA Wide VIN Synchronous Buck RegulatorSeptember 2014 Altera Corporation
Package Outline Drawing
L12.4x3
12 LEAD DUAL FLAT NO-LEAD PLASTIC PACKAGE
Rev 2, 7/10
1.70 +0.10/-0.15
12 X 0.40 ±0.10
12 0.10
12 x 0.23 +0.07/-0.054
7ABCM
PIN #1 INDEX AREA
61
2X 2.50
6
10X 0.50
3.30 +0.10/-0.15
TYPICAL RECOMMENDED LAND PATTERN
DETAIL "X"
TOP VIEW
BOTTOM VIEW
SIDE VIEW
located within the zone indicated. The pin #1 identifier may be
Unless otherwise specified, tolerance : Decimal ± 0.05
Tiebar shown (if present) is a non-functional feature.
The configuration of the pin #1 identifier is optional, but must be
between 0.15mm and 0.30mm from the terminal tip.
Dimension applies to the metallized terminal and is measured
Dimensions in ( ) for Reference Only.
Dimensioning and tolerancing conform to AMSE Y14.5m-1994.
6.
either a mold or mark feature.
3.
5.
4.
2.
Dimensions are in millimeters.1.
NOTES:
(4X) 0.15
3.00
INDEX AREA
6
PIN 1
4.00
B
A
1.00 MAX
SEE DETAIL "X"
C
SEATING PLANE
0.08C
0.10 C
( 3.30)
2.80
( 10X 0 . 5 )
( 12X 0.23 )
( 1.70 )
12 X 0.60
0.2 REF
C
0 . 05 MAX.
0 . 00 MIN.
5
Compliant to JEDEC MO-229 V4030D-4 issue E.7.
16
712
09616 September 3, 2014 Rev B
