MIC28303
50V, 3A Power Module
Features
General Description
• Easy to Use
- Stable with Low-Equivalent Series Resistance
(ESR) Ceramic Output Capacitor
- No Inductor and No Compensation to
Choose
• 4.5V to 50V Input Voltage
• Single-Supply Operation
• Power Good (PG) Output
• Low Radiated Emission (EMI) per EN55022, Class B
• Adjustable Current Limit
• Adjustable Output Voltage from 0.9V to 24V (Also
Limited by Duty Cycle)
• 200 kHz to 600 kHz, Programmable Switching
Frequency
• Supports Safe Start-Up into a Prebiased Output
• –40°C to +125°C Junction Temperature Range
• Available in 64-pin, 12 mm × 12 mm × 3 mm QFN
Package
MIC28303 is synchronous step-down regulator
module, featuring a unique adaptive ON-time control
architecture. The module incorporates a DC/DC
controller, power MOSFETs, bootstrap diode, bootstrap
capacitor and an inductor in a single package. The
MIC28303 operates over an input supply range from
4.5V-50V and can be used to supply up to 3A of output
current. The output voltage is adjustable down to 0.8V
with an accuracy of ±1%. The device operates with
programmable switching frequency from 200 kHz-600
kHz.
The MIC28303-1 uses HyperLight Load® architecture
for improved efficiency at light loads. The MIC28303-2
uses Hyper Speed Control® for ultra-fast transient
response.
The MIC28303 offers a full suite of protection features.
These include undervoltage lockout, internal soft-start,
foldback current limit, hiccup mode short-circuit
protection and thermal shutdown.
Applications
•
•
•
•
•
Distributed Power Systems
Industrial
Medical
Telecom
Automotive
Typical Application Circuit
MIC28303
12x12 QFN
VIN
4.5V to 50V
PVDD ANODE BSTC BSTR
PVIN
VIN
EN
C2,C3
2.2μF
VOUT
5V/3A
EN
VOUT
MIC28303
R3
16.5kΩ
SW
FREQ
ILIM
R19
75kΩ
PG
C1
100μF
R1
10kΩ
R15
3.57kΩ C10
0.1μF
C12
2.2nF
C14
47μF
FB
C6
10pF
PGOOD
R11
1.91kΩ
GND PGND
GND
2017 Microchip Technology Inc.
DS20005464B-page 1
MIC28303
Functional Block Diagram
100μF
2x2.2μF
CIN
CVIN
PVDD
BST
DH
CVDD
CONTROLLER
CBST
LIN
VOUT
ILIM-ADJ
DL
EN
N1
SW
2.2nF
16.5k
COUT
0.1μF
47μF
C10
FREQ
FB
FB
PGOOD
PGOOD
VOUT
5V/3A
C12
R3
FREQ
PVDD
R1
R15
2.7k 10k
ILIM
EN
R19
DNP
N2
SW
RFREQ
100k
ANODE
RBST
PVDD
49.9k
BSTC
DBST
VIN
VIN
VIN
PVIN
BSTR
VIN
4.5V to 50V
GND
PGND
R11
1.91k
PGND
GND
DS20005464B-page 2
2017 Microchip Technology Inc.
MIC28303
1.0
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings †
PVIN, VIN to PGND ...................................................................................................................................... –0.3V to +56V
PVDD, VANODE to PGND ................................................................................................................................ –0.3V to +6V
VSW, VFREQ, VILIM, VEN ................................................................................................................. –0.3V to (PVIN +0.3V)
VBSTC/BSTR to VSW......................................................................................................................................... –0.3V to 6V
VBSTC/BSTR to PGND ..................................................................................................................................... –0.3V to 56V
VFB, VPG to PGND ......................................................................................................................... –0.3V to (PVDD + 0.3V)
PGND to AGND ........................................................................................................................................... –0.3V to +0.3V
ESD Rating(1) ............................................................................................................................................. ESD Sensitive
Operating Ratings ‡
Supply Voltage (PVIN, VIN)............................................................................................................................. 4.5V to 50V
Enable Input (VEN) ..............................................................................................................................................0V to VIN
VSW, VFREQ, VILIM, VEN ......................................................................................................................................0V to VIN
Power Good (VPGOOD).................................................................................................................................... 0V to PVDD
† Notice: Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device.
This is a stress rating only and functional operation of the device at those or any other conditions above those indicated
in the operational sections of this specification is not intended. Exposure to maximum rating conditions for extended
periods may affect device reliability.
‡ Notice: The device is not guaranteed to function outside its operating ratings.
Note 1: Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5 kΩ in series
with 100 pF.
2017 Microchip Technology Inc.
DS20005464B-page 3
MIC28303
TABLE 1-1:
ELECTRICAL CHARACTERISTICS
Electrical Characteristics: PVIN = VIN = 12V, VOUT = 5V, VBST – VSW = 5V; TA = 25°C, unless noted. Bold values
indicate –40°C ≤ TJ ≤ +125°C. (Note 1).
Parameters
Min.
Typ.
Max.
Units
Conditions
Input Voltage Range (PVIN,
VIN)
4.5
—
50
V
Controller Supply Current
—
0.4
0.75
mA
—
2.1
3.0
—
0.1
10
µA
Current into Pin 60; VEN = 0V
—
0.7
—
mA
IOUT = 0A (MIC28303-1)
—
27
—
—
4.0
—
µA
PVIN = VIN = 12V, VEN = 0V
PVDD Output Voltage
4.8
5.2
5.4
V
VIN = 7V-50V, IPVDD = 10mA
PVDD UVLO Threshold
3.8
4.2
4.7
PVDD UVLO Hysteresis
—
400
—
mV
—
Load Regulation
0.6
2.0
3.6
%
IPVDD = 0 to 40mA
V
TJ = 25°C (±1.0%)
Power Supply Input
Operating Current
Shutdown Supply Current
—
Current into Pin 60; VFB = 1.5V
(MIC28303-1)
Current into Pin 60; VFB = 1.5V
(MIC28303-2)
IOUT = 0A (MIC28303-2)
PVDD Supply
PVDD rising
Reference
Feedback Reference Voltage
0.792
0.8
0.808
0.784
0.8
0.816
—
5
500
nA
VFB = 0.8V
EN Logic Level High
1.8
—
—
V
—
EN Logic Level Low
—
—
0.6
EN Hysteresis
—
200
—
mV
—
EN Bias Current
—
5
20
µA
VEN = 12V
400
600
750
kHz
FREQ pin = open
—
300
—
—
85
—
FB Bias Current
–40°C ≤ TJ ≤ 125°C (±2%)
Enable Control
—
Oscillator
Switching Frequency
Maximum Duty Cycle
Minimum Duty Cycle
RFREQ = 100 kΩ (FREQ pin-to-GND)
%
—
—
0
—
140
200
260
ns
—
—
5
—
ms
—
Current Limit Protection (VCL)
–30
–14
0
mV
VFB = 0.79V
Short-Circuit Threshold
–23
–7
9
mV
VFB = 0V
Minimum Off-Time
VFB > 0.8V
Soft-Start
Soft-Start Time
Short-Circuit Protection
Note 1:
Specification for packaged product only.
DS20005464B-page 4
2017 Microchip Technology Inc.
MIC28303
TABLE 1-1:
ELECTRICAL CHARACTERISTICS (CONTINUED)
Electrical Characteristics: PVIN = VIN = 12V, VOUT = 5V, VBST – VSW = 5V; TA = 25°C, unless noted. Bold values
indicate –40°C ≤ TJ ≤ +125°C. (Note 1).
Parameters
Min.
Typ.
Max.
Units
Conditions
Current-Limit Source Current
60
80
100
µA
Short-Circuit Source Current
27
36
47
—
—
50
µA
Power Good Threshold
Voltage
85
90
95
%VOUT
Power Good Hysteresis
—
6
—
Power Good Delay Time
—
100
—
µs
Sweep VFB from low-to-high
Power Good Low Voltage
—
70
200
mV
VFB < 90% x VNOM, IPG = 1 mA
Overtemperature Shutdown
—
160
—
°C
TJ rising
Overtemperature Shutdown
Hysteresis
—
4
—
Output Voltage Ripple
—
16
—
mV
IOUT = 3A
Line Regulation
—
0.36
—
%
PVIN = VIN = 7V to 50V, IOUT = 3A
Load Regulation
—
0.75
—
%
IOUT = 0A to 3A PVIN= VIN =12V
(MIC28303-1)
—
0.05
—
—
400
—
—
500
—
IOUT from 3A to 0A at 5 A/µs
(MIC28303-1)
—
400
—
IOUT from 0A to 3A at 5 A/µs
(MIC28303-2)
—
500
—
IOUT from 3A to 0A at 5 A/µs
(MIC28303-2)
VFB = 0.79V
VFB = 0V
Leakage
SW, BSTR Leakage Current
—
Power Good
Sweep VFB from low-to-high
Sweep VFB from high-to-low
Thermal Protection
—
Output Characteristic
Output Voltage Deviation from
Load Step
Note 1:
IOUT = 0A to 3A PVIN= VIN =12V
(MIC28303-2)
mV
IOUT from 0A to 3A at 5 A/µs
(MIC28303-1)
Specification for packaged product only.
2017 Microchip Technology Inc.
DS20005464B-page 5
MIC28303
TEMPERATURE SPECIFICATIONS
Parameters
Sym.
Min.
Typ.
Max.
Units
Conditions
Junction Operating Temperature
TJ
–40
—
+125
°C
Note 1
Temperature Ranges
Storage Temperature Range
TS
–65
—
+150
°C
—
Junction Temperature
TJ
—
—
+150
°C
—
Lead Temperature
—
—
—
+260
°C
Soldering, 10s
JA
—
20
—
°C/W
—
JC
—
5
—
°C/W
—
Package Thermal Resistances
Thermal Resistance 12 mm x 12 mm
QFN-64LD
Note 1:
The maximum allowable power dissipation is a function of ambient temperature, the maximum allowable
junction temperature and the thermal resistance from junction to air (i.e., TA, TJ, JA). Exceeding the
maximum allowable power dissipation will cause the device operating junction temperature to exceed the
maximum +125°C rating. Sustained junction temperatures above +125°C can impact the device reliability.
DS20005464B-page 6
2017 Microchip Technology Inc.
MIC28303
2.0
Note:
TYPICAL PERFORMANCE CURVES
The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
FIGURE 2-3:
(MIC28303-2).
FIGURE 2-1:
Efficiency vs. Output
Current (MIC28303-1).
Thermal Derating
FIGURE 2-2:
Efficiency vs. Output
Current (MIC28303-2).
TABLE 2-1:
RECOMMENDED COMPONENT VALUES FOR 275KHZ SWITCHING FREQUENCY
R1
(Top
Feedback
Resistor)
R11
(Bottom
Feedback
Resistor)
VIN
R3
(Rinj)
5V
7V-18V
16.5 kΩ
75 kΩ 3.57 kΩ
10 kΩ
1.9 kΩ
0.1 µF
2.2 nF
2 x 47 µF/6.3V
5V
18V-50V
39.2 kΩ
75 kΩ 3.57 kΩ
10 kΩ
1.9 kΩ
0.1 µF
2.2 nF
2 x 47 µF/6.3V
3.3V
5V-18V
16.5 kΩ
75 kΩ 3.57 kΩ
10 kΩ
3.24 kΩ
0.1 µF
2.2 nF
2 x 47 µF/6.3V
3.3V
18V-50V
39.2 kΩ
75 kΩ 3.57 kΩ
10 kΩ
3.24 kΩ
0.1 µF
2.2 nF
2 x 47 µF/6.3V
VOUT
2017 Microchip Technology Inc.
R19
R15
C10
(Cinj)
C12
(Cff)
COUT
DS20005464B-page 7
MIC28303
FIGURE 2-4:
VIN Operating Supply vs.
Input Voltage (MIC28303-1).
FIGURE 2-7:
VIN Operating Supply
Current vs. Temperature (MIC28303-1).
FIGURE 2-5:
Output Regulation vs. Input
Voltage (MIC28303-1).
FIGURE 2-8:
Load Regulation vs.
Temperature (MIC28303-1).
FIGURE 2-6:
Output Voltage vs. Input
Voltage (MIC28303-1).
FIGURE 2-9:
Line Regulation vs.
Temperature (MIC28303-1).
DS20005464B-page 8
2017 Microchip Technology Inc.
MIC28303
.
FIGURE 2-10:
Line Regulation vs.
Temperature (MIC28303-1).
FIGURE 2-13:
FIGURE 2-11:
Line Regulation vs. Output
Current (MIC28303-1).
FIGURE 2-14:
Efficiency vs. Output
Current (MIC28303-1).
FIGURE 2-12:
Efficiency (VIN = 12V) vs.
Output Current (MIC28303-1).
FIGURE 2-15:
VIN Operating Supply
Current vs. Input Voltage (MIC28303-2).
2017 Microchip Technology Inc.
Efficiency (VIN = 24V) vs.
Output Current (MIC28303-1).
DS20005464B-page 9
MIC28303
FIGURE 2-16:
Output Regulation vs. Input
Voltage (MIC28303-2).
FIGURE 2-19:
Input Voltage.
ENABLE THRESHOLD (V)
1.50
Switching Frequency vs.
Rising
1.20
Falling
0.90
0.60
Hyst
0.30
0.00
10 15 20 25 30 35 40 45 50 55 60 65 70 75
INPUT VOLTAGE (V)
FIGURE 2-17:
Input Voltage.
VIN Shutdown Current vs.
FIGURE 2-20:
Voltage.
Enable Threshold vs. Input
FIGURE 2-18:
vs. Input Voltage.
Output Peak Current Limit
FIGURE 2-21:
Temperature.
VIN Shutdown Current vs.
DS20005464B-page 10
2017 Microchip Technology Inc.
MIC28303
FIGURE 2-22:
vs. Temperature.
Output Peak Current Limit
FIGURE 2-25:
VIN Operating Supply
Current vs. Temperature (MIC28303-2).
FIGURE 2-23:
Temperature.
EN Bias Current vs.
FIGURE 2-26:
Load Regulation vs.
Temperature (MIC28303-2).
FIGURE 2-24:
Temperature.
Enable Threshold vs.
FIGURE 2-27:
Line Regulation vs.
Temperature (MIC28303-2).
2017 Microchip Technology Inc.
DS20005464B-page 11
MIC28303
FIGURE 2-28:
Line Regulation vs.
Temperature (MIC28303-2).
FIGURE 2-31:
Efficiency (VIN = 12V) vs.
Output Current (MIC28303-2).
FIGURE 2-29:
Switching Frequency vs.
Temperature (MIC28303-2).
FIGURE 2-32:
Efficiency (VIN = 24V) vs.
Output Current (MIC28303-2).
FIGURE 2-30:
Line Regulation vs. Output
Current (MIC28303-2).
FIGURE 2-33:
Efficiency (VIN = 38V) vs.
Output Current (MIC28303-2).
DS20005464B-page 12
2017 Microchip Technology Inc.
MIC28303
FIGURE 2-34:
Switching Frequency.
FIGURE 2-37:
(MIC28303-2).
Thermal Derating
FIGURE 2-35:
(MIC28303-2).
Thermal Derating
FIGURE 2-38:
(MIC28303-2)
Thermal Derating
FIGURE 2-36:
(MIC28303-2).
Thermal Derating
2017 Microchip Technology Inc.
DS20005464B-page 13
MIC28303
T.
TABLE 2-2:
RECOMMENDED COMPONENT VALUES FOR 600 KHZ SWITCHING FREQUENCY
R1
R11
(Top
(Bottom
Feedback Feedback
Resistor) Resistor)
VOUT
VIN
R3
(Rinj)
R19
C10
(Cinj)
C12
(Cff)
0.9V
5V-50V
16.5 kΩ
10 kΩ
80.6 kΩ
DNP
0.1 µF
2.2 nF
47 µF/6.3V
or 2 x 22 µF
1.2V
5V-50V
16.5 kΩ
10 kΩ
20 kΩ
DNP
0.1 µF
2.2 nF
47 µF/6.3V
or 2 x 22 µF
1.8V
5V-50V
16.5 kΩ
10 kΩ
8.06 kΩ
DNP
0.1 µF
2.2 nF
47 µF/6.3V
or 2 x 22 µF
2.5V
5V-50V
16.5 kΩ
10 kΩ
4.75 kΩ
DNP
0.1 µF
2.2 nF
47 µF/6.3V
or 2 x 22 µF
3.3V
5V-50V
16.5 kΩ
10 kΩ
3.24 kΩ
DNP
0.1 µF
2.2 nF
47 µF/6.3V
or 2 x 22 µF
5V
7V-50V
16.5 kΩ
10 kΩ
1.9 kΩ
DNP
0.1 µF
2.2 nF
47 µF/6.3V
or 2 x 22 µF
12V
18V-50V
23.2 kΩ
10 kΩ
715 kΩ
DNP
0.1 µF
2.2 nF
47 µF/16V
or 2 x 22 µF
VEN
(2V/div)
VIN
(10V/div)
VIN = 12V
VOUT = 5V
IOUT = 3A
VOUT
(2V/div)
VSW
(10V/div)
VOUT
(2V/div)
Time (4.0ms/div)
Enable Turn-On Delay and
FIGURE 2-41:
MIC28303-2 VIN Start-Up
with Pre-Biased Output.
VIN
(10V/div)
VEN
(2V/div)
VIN = 12V
VOUT = 5V
IOUT = 3A
VOUT
(2V/div)
VOUT
(2V/div)
VSW
(10V/div)
VSW
(10V/div)
Time (1.0ms/div)
FIGURE 2-40:
Fall Time.
DS20005464B-page 14
VIN = 12V
VOUT = 5V
IOUT = 0A
VPRE-BIAS = 1.5V
VSW
(10V/div)
Time (2.0ms/div)
FIGURE 2-39:
Rise Time.
COUT
Enable Turn-Off Delay and
VIN = 12V
VOUT = 5V
IOUT = 0A
VPRE-BIAS = 1.5V
Time (4.0ms/div)
FIGURE 2-42:
MIC28303-1 VIN Start-Up
with Pre-Biased Output.
2017 Microchip Technology Inc.
MIC28303
VEN
(2V/div)
VIN = 12V
VOUT = 5V
IOUT = SHORT
VIN
(10V/div)
VIN = 12V
VOUT = 5V
IOUT = 3A
VOUT
(20mV/div)
VOUT
(2V/div)
VSW
(10V/div)
VSW
(10V/div)
Time (10ms/div)
FIGURE 2-43:
Time (2.0ms/div)
Enable Turn-On/Turn-Off.
FIGURE 2-46:
Power-Up into Short-Circuit.
VEN
(2V/div)
VEN
(1V/div)
VIN = 12V
VOUT = 5V
IOUT = SHORT
VOUT
(20mV/div)
VIN = 12V
VOUT = 5V
IOUT = 3A
VOUT
(2V/div)
VSW
(10V/div)
Time (10ms/div)
FIGURE 2-44:
Time (400μs/div)
Enable Thresholds.
VOUT = 3.3V
IOUT = 1.0A
FIGURE 2-47:
Enabled into Short.
VOUT
(5V/div)
VIN = 12V
VOUT = 5V
VIN
(1V/div)
VOUT
(2V/div)
IOUT
(5A/div)
Time (20ms/div)
FIGURE 2-45:
UVLO Thresholds.
2017 Microchip Technology Inc.
Time (40ms/div)
FIGURE 2-48:
Threshold.
Output Peak Current-Limit
DS20005464B-page 15
MIC28303
VIN = 12V
VOUT = 5V
VOUT
(AC-COUPLED)
(100mV/div)
VOUT
(2V/div)
VIN = 12V
VOUT = 5V
IOUT = 10mA TO 500mA
IOUT
(5A/div)
IOUT
(500mA/div)
Time (100μs/div)
Time (100μs/div)
FIGURE 2-49:
Short Circuit.
FIGURE 2-52:
Response.
MIC28303-2 Transient
FIGURE 2-53:
Response.
MIC28303-2 Transient
VIN = 12V
VOUT = 5V
IOUT = 1A
VOUT
(2V/div)
VSW
(10V/div)
Time (2.0ms/div)
FIGURE 2-50:
Output Recovery from
Thermal Shutdown.
VOUT
(AC-COUPLED)
(20mV/div)
VIN = 12V
VOUT = 5V
IOUT = 3A
VSW
(10V/div)
VOUT
(AC-COUPLED)
(100mV/div)
VIN = 12V
VOUT = 5V
IOUT = 10mA TO 500mA
IOUT
(500mA/div)
Time (1.0μs/div)
FIGURE 2-51:
MIC28303-2 Switching
Waveforms (IOUT = 3A).
DS20005464B-page 16
Time (100μs/div)
FIGURE 2-54:
Response.
MIC28303-1 Transient
2017 Microchip Technology Inc.
MIC28303
VOUT
(AC-COUPLED)
(200mV/div)
VOUT
(AC-COUPLED)
(500mV/div)
VIN = 12V
VOUT = 5V
IOUT = 500mA TO 2A
IOUT
(1A/div)
VIN = 12V
VOUT = 5V
IOUT = 1A TO 3A
IOUT
(2A/div)
Time (100μs/div)
FIGURE 2-55:
Response.
MIC28303-2 Transient
VOUT
(AC-COUPLED)
(200mV/div)
Time (100μs/div)
FIGURE 2-58:
Response.
VIN
(10V/div)
VIN = 12V
VOUT = 5V
IOUT = 500mA TO 2A
IOUT
(1A/div)
VIN = 12V
VOUT = 5V
IOUT = 0A
VOUT
(5V/div)
VPG
(5V/div)
Time (2.0ms/div)
Time (100μs/div)
FIGURE 2-56:
Response.
MIC28303-1 Transient
MIC28303-1 Transient
VOUT
(AC-COUPLED)
(500mV/div)
FIGURE 2-59:
Turn-On.
Power Good at VIN Soft
VIN
(10V/div)
VIN = 12V
VOUT = 5V
IOUT = 1A TO 3A
VIN = 12V
VOUT = 5V
IOUT = 0A
VOUT
(5V/div)
IOUT
(2A/div)
VPG
(5V/div)
Time (100μs/div)
FIGURE 2-57:
Response.
MIC28303-2 Transient
2017 Microchip Technology Inc.
Time (20ms/div)
FIGURE 2-60:
Turn-Off.
Power Good at VIN Soft
DS20005464B-page 17
MIC28303
FIGURE 2-61:
Radiated Emissions –
30 MHz to 1000 MHz (VIN = 12V/IOUT = 2A).
FIGURE 2-62:
Radiated Emissions –
30 MHz to 1000 MHz (VIN = 36V/IOUT = 2A).
FIGURE 2-63:
Radiated Emissions –
30 MHz to 1000 MHz (VIN = 12V/IOUT = 3A).
DS20005464B-page 18
2017 Microchip Technology Inc.
MIC28303
3.0
PIN DESCRIPTIONS
Package Type
BSTC
SW
BSTR
56
51
FB
57
BSTC
PGOOD
58
53
EN
59
52
VIN
60
BSTR
PVDD
61
GND
PVDD
62
54
NC
63
55
GND
64
MIC28303
64-Pin 12 mm x 12 mm QFN (MP)
39
NC
PGND
13
38
VOUT
PVIN
14
37
VOUT
PVIN
15
36
VOUT
PVIN
16
35
VOUT
PVIN
17
34
VOUT
PVIN
18
33
VOUT
32
12
VOUT
SW
PGND
31
40
30
11
VOUT
SW
PGND
VOUT
41
29
10
VOUT
SW
PGND
28
42
VOUT
9
27
SW
PGND
VOUT
43
26
8
VOUT
SW
FREQ
25
44
VOUT
7
24
SW
FREQ
VOUT
45
23
6
VOUT
SW
SW
22
46
PVIN
5
21
SW
VIN
PVIN
SW
47
20
48
4
GND
ILIM
19
3
2
PVIN
ANODE
ANODE
1
GND
PVIN
49
GND
50
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1:
PIN FUNCTION TABLE
Pin Number
Symbol
Description
1, 2, 3, 54, 64
GND
Analog Ground. Ground for internal controller and feedback resistor network. The
analog ground return path should be separate from the power ground (PGND) return
path.
4
ILIM
Current Limit Setting. Connect a resistor from SW (Pin 6) to ILIM to set the
overcurrent threshold for the converter.
5, 60
VIN
Supply Voltage for Controller. The VIN operating voltage range is from 4.5V-50V. A
0.47 μF ceramic capacitor from VIN (pin 60) to GND is required for decoupling. Pin
5 should be externally connected to either PVIN or Pin 60 on PCB.
6, 40 to 48, 51
SW
Switch Node and Current-Sense Input. High current output driver return. The SW
pin connects directly to the switch node. Due to the high-speed switching on this
pin, the SW pin should be routed away from sensitive nodes. The SW pin also
senses the current by monitoring the voltage across the low-side MOSFET during
OFF time.
7, 8
FREQ
Switching Frequency Adjust Input. Leaving this pin open will set the switching
frequency to 600 kHz. Alternatively, a resistor from this pin to ground can be used
to lower the switching frequency.
9 to 13
PGND
Power Ground. PGND is the return path for the buck converter power stage. The
PGND pin connects to the sources of low-side N-Channel external MOSFET, the
negative terminals of input capacitors and the negative terminals of output
capacitors. The return path for the power ground should be as small as possible
and separate from the analog ground (GND) return path.
14 to 22
PVIN
Power Input Voltage. Connection to the drain of the internal high-side power
MOSFET.
23 to 38
VOUT
Output Voltage. Connection with the internal inductor, the output capacitor should
be connected from this pin to PGND as close to the module as possible.
39
NC
2017 Microchip Technology Inc.
No Connection. Leave it floating.
DS20005464B-page 19
MIC28303
TABLE 3-1:
PIN FUNCTION TABLE (CONTINUED)
Pin Number
Symbol
49, 50
ANODE
52, 53
BSTC
Bootstrap Capacitor. Connection to the internal bootstrap capacitor. Leave floating,
no connection.
55, 56
BSTR
Bootstrap Resistor. Connection to the internal bootstrap resistor and high-side
power MOSFET drive circuitry. Leave floating, no connect.
57
FB
58
PGOOD
59
EN
Enable Input. A logic signal to enable or disable the buck converter operation. The
EN pin is CMOS compatible. Logic high enables the device, logic low shuts down
the regulator. In the disable mode, the input supply current for the device is
minimized to 4 µA typically. Do not pull EN to PVDD.
61, 62
PVDD
Internal +5V Linear Regulator Output. PVDD is the internal supply bus for the
device. In the applications with VIN < +5.5V, PVDD should be tied to VIN to bypass
the linear regulator.
63
NC
DS20005464B-page 20
Description
Anode Bootstrap Diode Input. Anode connection of internal bootstrap diode. This
pin should be connected to the PVDD pin.
Feedback Input. Input to the transconductance amplifier of the control loop. The FB
pin is regulated to 0.8V. A resistor divider connecting the feedback to the output is
used to set the desired output voltage.
Power Good Output. Open-drain output. An external pull-up resistor to external
power rails is required.
No Connection. Leave it floating.
2017 Microchip Technology Inc.
MIC28303
4.0
FUNCTIONAL DESCRIPTION
The MIC28303 is an adaptive on-time synchronous
buck regulator module built for high-input voltage to
low-output voltage conversion applications. The
MIC28303 is designed to operate over a wide input
voltage range, from 4.5V-50V, and the output is
adjustable with an external resistor divider. An adaptive
ON-time control scheme is employed to obtain a
constant switching frequency and to simplify the control
compensation. Hiccup mode overcurrent protection is
implemented by sensing low-side MOSFET’s RDS(ON).
The device features internal soft-start, enable, UVLO
and thermal shutdown. The module has integrated
switching FETs, as well as an inductor, bootstrap diode,
resistor and capacitor.
4.1
Theory of Operation
Per the Functional Diagram of the MIC28303 module,
the output voltage is sensed by the MIC28303
feedback pin FB via the voltage divider R1 and R11,
and compared to a 0.8V reference voltage VREF at the
error comparator through a low-gain transconductance
(gm) amplifier. If the feedback voltage decreases and
the amplifier output is below 0.8V, then the error
comparator will trigger the control logic and generate
an ON-time period. The ON-time period length is
predetermined by the Fixed tON Estimator circuitry:
EQUATION 4-1:
V OUT
t ON ESTIMATED = ---------------------V IN f SW
Where:
VOUT
Output Voltage
VIN
Power Stage Input Voltage
fSW
Switching Frequency
At the end of the ON-time period, the internal high-side
driver turns off the high-side MOSFET and the low-side
driver turns on the low-side MOSFET. The OFF-time
period length depends on the feedback voltage in most
cases. When the feedback voltage decreases and the
output of the gm amplifier is below 0.8V, the ON-time
period is triggered and the OFF-time period ends. If the
OFF-time period determined by the feedback voltage is
less than the minimum OFF-time tOFF(MIN), which is
about 200 ns, the MIC28303 control logic will apply the
tOFF(MIN) instead. tOFF(MIN) is required to maintain
enough energy in the boost capacitor (CBST) to drive
the high-side MOSFET.
The maximum duty cycle is obtained from the 200 ns
tOFF(MIN):
2017 Microchip Technology Inc.
EQUATION 4-2:
Where:
t S – t OFF MIN
D MAX = ---------------------------------- = 1 – 200ns
--------------tS
tS
1/fSW
tS
It is not recommended to use MIC28303 with an
OFF-time close to tOFF(MIN) during steady-state
operation.
The adaptive ON-time control scheme results in a
constant switching frequency in the MIC28303. The
actual ON-time and resulting switching frequency will
vary with the different rising and falling times of the
external MOSFETs. Also, the minimum tON results in a
lower switching frequency in high VIN to VOUT
applications. During load transients, the switching
frequency is changed due to the varying OFF-time.
To illustrate the control loop operation, both the
steady-state and load transient scenarios were
analyzed. For easy analysis, the gain of the gm
amplifier is assumed to be 1. With this assumption, the
inverting input of the error comparator is the same as
the feedback voltage.
Figure 4-1 shows the MIC28303 control loop timing
during steady-state operation. During steady state, the
gm amplifier senses the feedback voltage ripple, which
is proportional to the output voltage ripple plus injected
voltage ripple, to trigger the ON-time period. The
ON-time is predetermined by the tON estimator. The
termination of the OFF-time is controlled by the
feedback voltage. At the valley of the feedback voltage
ripple, which occurs when VFB falls below VREF, the
OFF period ends and the next ON-time period is
triggered through the control logic circuitry.
IL
ΔIL(PP)
IOUT
VOUT
ΔVOUT(PP) = ESRCOUT × ΔIL(PP)
VFB
ΔVFB(PP) = ΔVOUT(PP) ×
VREF
R2
R1+R2
TRIGGER ON-TIME IF VFB IS BELOW VREF
DH
ESTIMATED ON-TIME
FIGURE 4-1:
Timing
MIC28303 Control Loop
Figure 4-2 shows the operation of the MIC28303 during
a load transient. The output voltage drops due to the
sudden load increase, which causes the VFB to be less
than VREF. This will cause the error comparator to
trigger an ON-time period. At the end of the ON-time
period, a minimum OFF-time tOFF(MIN) is generated to
DS20005464B-page 21
MIC28303
charge the bootstrap capacitor (CBST) because the
feedback voltage is still below VREF. Then, the next
ON-time period is triggered due to the low feedback
voltage. Therefore, the switching frequency changes
during the load transient, but returns to the nominal
fixed frequency once the output has stabilized at the
new load current level. With the varying duty cycle and
switching frequency, the output recovery time is fast
and the output voltage deviation is small.
FULL LOAD
IOUT
NO LOAD
VOUT
VREF
VFB
DH
TOFF(min)
FIGURE 4-2:
Response
MIC28303 Load Transient
Unlike true current-mode control, the MIC28303 uses
the output voltage ripple to trigger an ON-time period.
The output voltage ripple is proportional to the inductor
current ripple if the ESR of the output capacitor is large
enough.
In order to meet the stability requirements, the
MIC28303 feedback voltage ripple should be in phase
with the inductor current ripple and be large enough to
be sensed by the gm amplifier and the error
comparator. The recommended feedback voltage
ripple is 20 mV ~ 100 mV over the full input voltage
range. If a low ESR output capacitor is selected, then
the feedback voltage ripple may be too small to be
sensed by the gm amplifier and the error comparator.
Also, the output voltage ripple and the feedback
voltage ripple are not necessarily in phase with the
inductor current ripple if the ESR of the output capacitor
is very low. In these cases, ripple injection is required
to ensure proper operation. Please refer to
“Section 5.6, Ripple Injection” for more details about
the ripple injection technique.
4.2
Discontinuous Mode (MIC28303-1
Only)
In continuous mode, the inductor current is always
greater than zero; however, at light loads, the
MIC28303-1 is able to force the inductor current to
operate in discontinuous mode. Discontinuous mode is
where the inductor current falls to zero, as indicated by
trace (IL) shown in Figure 4-3. During this period, the
efficiency is optimized by shutting down all the
non-essential circuits and minimizing the supply
current. The MIC28303-1 wakes up and turns on the
high-side MOSFET when the feedback voltage VFB
drops below 0.8V.
The MIC28303-1 has a zero crossing comparator (ZC)
that monitors the inductor current by sensing the
voltage drop across the low-side MOSFET during its
ON-time. If the VFB > 0.8V and the inductor current
goes slightly negative, then the MIC28303-1
automatically powers down most of the IC’s circuitry
and goes into a low-power mode.
Once the MIC28303-1 goes into discontinuous mode,
both DL and DH are low, which turns off the high-side
and low-side MOSFETs. The load current is supplied
by the output capacitors and VOUT drops. If the drop of
VOUT causes VFB to go below VREF, then all the circuits
will wake up into normal continuous mode. First, the
bias currents of most circuits reduced during the
discontinuous mode are restored, and then a tON pulse
is triggered before the drivers are turned on to avoid
any possible glitches. Finally, the high-side driver is
turned on. Figure 4-3 shows the control loop timing in
discontinuous mode.
IL CROSSES 0 and VFB > 0.8
DISCONTINUOUS MODE STARTS
VFB < 0.8. WAKE UP FROM
DISCONTINUOUS MODE
DH
DL
ESTIMATED ON-TIME
FIGURE 4-3:
MIC28303-1 Control Loop
Timing (Discontinuous Mode)
DS20005464B-page 22
2017 Microchip Technology Inc.
MIC28303
During discontinuous mode, the bias current of most
circuits is substantially reduced. As a result, the total
power supply current during discontinuous mode is
only about 400 μA, allowing the MIC28303-1 to achieve
high efficiency in light load applications.
4.3
Soft-Start
Soft-start reduces the input power supply surge current
at start-up by controlling the output voltage rise time.
The input surge appears while the output capacitor is
charged up. A slower output rise time will draw a lower
input surge current.
The MIC28303 implements an internal digital soft-start
by making the 0.8V reference voltage VREF ramp from
0 to 100% in about 5 ms with 9.7 mV steps. Therefore,
the output voltage is controlled to increase slowly by a
staircase VFB ramp. Once the soft-start cycle ends, the
related circuitry is disabled to reduce current
consumption. PVDD must be powered up at the same
time or after VIN to make the soft-start function
correctly.
4.4
Current Limit
The MIC28303 uses the RDS(ON) of the low side
MOSFET and external resistor connected from ILIM pin
to SW node to decide the current limit.
The VCL drop allows short-limit programming through
the value of the resistor (R15), if the absolute value of
the voltage drop on the bottom FET is greater than VCL.
In that case, the V(ILIM) is lower than PGND and a short
circuit event is triggered. A hiccup cycle to treat the
short event is generated. The hiccup sequence,
including the soft-start, reduces the stress on the
switching FETs and protects the load and supply for
severe short conditions.
The short-circuit current limit can be programmed by
using Equation 4-3.
EQUATION 4-3:
I CLIM – I L PP 0.5 R DS ON + V CL
R15 = ---------------------------------------------------------------------------------------------------I CL
Where:
ICLIM
Desired Current Limit
RDS(ON)
On-Resistance of Low-Side Power
MOSFET, 57 mΩ Typically
VCL
Current-Limit Threshold (Typical
Absolute Value is 14 mV per Table 1-1)
ICL
Current-Limit Source Current (Typical
Value is 80 µA, per Table 1-1)
∆IL(PP)
Inductor Current Peak-to-Peak.
Because the inductor is integrated, use Equation 4-4 to
calculate the peak-to-peak inductor ripple current.
MIC28303
VIN
EQUATION 4-4:
VIN
BST
2.2μF
x3
V OUT V IN MAX – V OUT
I L PP = ------------------------------------------------------------------V IN MAX f SW L
SW
SW
CS
R15
ILIM
C6
FB
PGND
FIGURE 4-4:
Current-Limiting Circuit
In each switching cycle of the MIC28303, the inductor
current is sensed by monitoring the low-side MOSFET
in the OFF period. The sensed voltage V(ILIM) is
compared with the power ground (PGND) after a
blanking time of 150 ns. In this way, the drop voltage
over the resistor R15 (VCL) is compared with the drop
over the bottom FET, generating the short current limit.
The small capacitor (C6) connected from the ILIM pin to
PGND filters the switching node ringing during the
OFF-time, allowing a better short limit measurement.
The time constant created by R15 and C6 should be
much less than the minimum OFF-time.
2017 Microchip Technology Inc.
The MIC28303 has 4.7 µH inductor integrated into the
module. The typical value of RWINDING(DCR) of this
particular inductor is in the range of 45 mΩ.
In case of hard short, the short limit is folded down to
allow an indefinite hard short on the output without any
destructive effect. It is mandatory to make sure that the
inductor current used to charge the output capacitance
during soft start is under the folded short limit;
otherwise, the supply will go into hiccup mode and may
not finish the soft-start successfully.
The MOSFET RDS(ON) varies 30%-40% with
temperature; therefore, it is recommended to add a
50% margin to ICLIM in Equation 4-3 to avoid false
current limiting due to increased MOSFET junction
temperature rise. Table 4-1 shows typical output
current limit value for a given R15 with C6 = 10 pF.
TABLE 4-1:
TYPICAL OUTPUT
CURRENT-LIMIT VALUES
R15
Typical Output Current-Limit
1.81 kΩ
3A
2.7 kΩ
6.3A
DS20005464B-page 23
MIC28303
5.0
APPLICATION INFORMATION
5.1
Simplified Input Transient
Circuitry
EQUATION 5-1:
R19
f SW ADJ = f O --------------------------------R19 + 100k
Where:
The 56V absolute maximum rating of the MIC28303
allows simplifying the transient voltage suppressor on
the input supply side, which is very common in
industrial applications. The input supply voltage VIN
(Figure 5-1) may be operating at 12V input rail most of
the time, but can encounter a noise spike of 50V for a
short duration. By using MIC28303, which has 56V
absolute maximum voltage rating, the input transient
suppressor is not needed. This saves on component
count and form factor, and ultimately the system
becomes less expensive.
Switching Frequency When R19 is
Open
fO
For more precise setting, it is recommended to use
Figure 5-3:
50V
12V
VIN
FIGURE 5-1:
Circuitry.
5.2
MIC28303
MODULE
VOUT
Simplified Input Transient
Setting the Switching Frequency
The MIC28303 switching frequency can be adjusted by
changing the value of resistor R19. The top resistor of
100 kΩ is internal to module and is connected between
VIN and FREQ pin, so the value of R19 sets the
switching frequency. The switching frequency also
depends on VIN, VOUT and load conditions.
MIC28303
BST
VIN
VIN
2.2μF
x3
RFREQ
FREQ 100kΩ
R19
SW
CS
FB
PGND
FIGURE 5-2:
Adjustment.
Switching Frequency
Equation 5-1 gives the estimated switching frequency:
DS20005464B-page 24
FIGURE 5-3:
R19
5.3
Switching Frequency vs.
Output Capacitor Selection
The type of the output capacitor is usually determined
by the application and its equivalent series resistance
(ESR). Voltage and RMS current capability are two
other important factors for selecting the output
capacitor. Recommended capacitor types are MLCC,
tantalum, low-ESR aluminum electrolytic, OS-CON and
POSCAP. The output capacitor’s ESR is usually the
main cause of the output ripple. The MIC28303
requires ripple injection and the output capacitor ESR
effects the control loop from a stability point of view.
The maximum value of ESR is calculated as in
Equation 5-2:
EQUATION 5-2:
ESR C
OUT
V OUT PP
--------------------------I L PP
Where:
∆VOUT(PP)
Peak-to-Peak Output Voltage Ripple
∆IL(PP)
Peak-to-Peak Inductor Current Ripple
2017 Microchip Technology Inc.
MIC28303
The total output ripple is a combination of the ESR and
output capacitance. The total ripple is calculated in
Equation 5-3:
derating. The input voltage ripple will primarily depend
on the input capacitor’s ESR. The peak input current is
equal to the peak inductor current, so that:
EQUATION 5-3:
EQUATION 5-6:
V IN = I L pk ESR CIN
V OUT PP =
2
I L PP
2
-------------------------------------
C OUT f SW 8 + I L PP ESR C OUT
Where:
D
Duty Cycle
COUT
Output Capacitance Value
fSW
Switching Frequency
As described in Section 4.1, Theory of Operation, the
MIC28303 requires at least 20 mV peak-to-peak ripple
at the FB pin to make the gm amplifier and the error
comparator behave properly. Also, the output voltage
ripple should be in phase with the inductor current.
Therefore, the output voltage ripple caused by the
output capacitors value should be much smaller than
the ripple caused by the output capacitor ESR. If
low-ESR capacitors such as ceramic capacitors are
selected as the output capacitors, a ripple injection
method should be applied to provide enough feedback
voltage ripple. Please refer to Section 5.6, Ripple
Injection for more details.
The voltage rating of the capacitor should be twice the
output voltage for a tantalum and 20% greater for
aluminum electrolytic or OS-CON.
The output capacitor RMS current is calculated in
Equation 5-4:
The input capacitor must be rated for the input current
ripple. The RMS value of input capacitor current is
determined at the maximum output current. Assuming
the peak-to-peak inductor current ripple is low:
EQUATION 5-7:
I CIN RMS I OUT MAX D 1 – D
The power dissipated in the input capacitor is:
EQUATION 5-8:
2
P DISS CIN = I CIN RMS ESR CIN
The general rule is to pick the capacitor with a ripple
current rating equal to or greater than the calculated
worst (VIN_MAX) case RMS capacitor current. Its
voltage rating should be 20%-50% higher than the
maximum input voltage. Typically the input ripple (dV)
needs to be kept down to less than ±10% of input
voltage. The ESR also increases the input ripple.
Equation 5-9 should be used to calculate the input
capacitor. Also it is recommended to keep some margin
on the calculated value:
EQUATION 5-9:
I OUT MAX 1 – D
C IN --------------------------------------------------f SW dV
EQUATION 5-4:
IC
OUT RMS
I L PP
= ----------------12
Where:
The power dissipated in the output capacitor is:
dV
Input Ripple
fSW
Switching Frequency
EQUATION 5-5:
P DISS C
5.4
OUT
= IC
2
OUT RMS
ESR C
OUT
Input Capacitor Selection
The input capacitor for the power stage input PVIN
should be selected for ripple current rating and voltage
rating. Tantalum input capacitors may fail when
subjected to high inrush currents, caused by turning the
input supply on. A tantalum input capacitor’s voltage
rating should be at least two times the maximum input
voltage to maximize reliability. Aluminum electrolytic,
OS-CON, and multilayer polymer film capacitors can
handle the higher inrush currents without voltage
2017 Microchip Technology Inc.
DS20005464B-page 25
MIC28303
5.5
Output Voltage Setting
Components
The MIC28303 requires two resistors to set the output
voltage, as shown in Figure 5-4:
injection method is applied for low output voltage ripple
applications. Table 2-2 summarizes the ripple injection
component values for ceramic output capacitor.
The applications are divided into three situations
according to the amount of the feedback voltage ripple:
• Enough ripple at the feedback voltage due to the
large ESR of the output capacitors (Figure 5-5):
R1
VOUT
FB
gm Amp
R11
MIC28303
R1
COUT
FB
R11
ESR
VREF
FIGURE 5-5:
Enough Ripple at FB.
As shown in Figure 5-6, the converter is stable
without any ripple injection.
FIGURE 5-4:
Configuration.
Voltage-Divider
VOUT
The output voltage is determined by Equation 5-10:
MIC28303
EQUATION 5-10:
R1
FB
Cff
R11
R1-
V OUT = V FB 1 + --------
R11
COUT
ESR
Where:
VFB
0.8V
A typical value of R1 used on the standard evaluation
board is 10 kΩ. If R1 is too large, it may allow noise to
be introduced into the voltage feedback loop. If R1 is
too small in value, it will decrease the efficiency of the
power supply, especially at light loads. Once R1 is
selected, R11 can be calculated using Equation 5-11:
EQUATION 5-11:
V FB R1
R11 = ----------------------------V OUT – V FB
5.6
Ripple Injection
The VFB ripple required for proper operation of the
MIC28303 gm amplifier and error comparator is 20 mV
to 100 mV. However, the output voltage ripple is
generally designed as 1%-2% of the output voltage.
For a low output voltage, such as a 1V, the output
voltage ripple is only 10 mV-20 mV, and the feedback
voltage ripple is less than 20 mV. If the feedback
voltage ripple is so small that the gm amplifier and error
comparator cannot sense it, then the MIC28303 will
lose control and the output voltage is not regulated. In
order to have some amount of VFB ripple, a ripple
DS20005464B-page 26
FIGURE 5-6:
Inadequate Ripple at FB.
The feedback voltage ripple is:
EQUATION 5-12:
R11
V FB PP = ----------------------- ESR C I L PP
OUT
R1 + R11
Where:
∆IL(PP)
Peak-to-Peak Value of the Inductor
Current Ripple
• Inadequate ripple at the feedback voltage due to
the small ESR of the output capacitors, such is
the case with ceramic output capacitor.
The output voltage ripple is fed into the FB pin
through a feed-forward capacitor, Cff in this situation,
as shown in Figure 5-7. The typical Cff value is
between 1 nF and 100 nF.
2017 Microchip Technology Inc.
MIC28303
1.
VOUT
SW
MIC28303
Cinj
Rinj
R1
Cff
COUT
FB
R11
FIGURE 5-7:
ESR
Invisible Ripple at FB.
2.
EQUATION 5-17:
With the feed-forward capacitor, the feedback
voltage ripple is very close to the output voltage
ripple.
f SW
V FB PP
K div = ----------------------- ---------------------------V IN
D 1 – D
Then the value of Rinj is obtained as:
EQUATION 5-13:
V FB PP ESR I L PP
EQUATION 5-18:
1 - – 1
R inj = R1 R11 --------K div
• Virtually no ripple at the FB pin voltage due to the
very low ESR of the output capacitors.
In this situation, the output voltage ripple is less than
20 mV. Therefore, additional ripple is injected into the
FB pin from the switching node SW via a resistor Rinj
and a capacitor Cinj, as shown in Figure 5-7. The
injected ripple is:
EQUATION 5-14:
V FB PP
Select Cff to feed all output ripples into the feedback pin and make sure the large time constant
assumption is satisfied. Typical choice of Cff is
1 nF to 100 nF if R1 and R11 are in the kΩ
range.
Select Rinj according to the expected feedback
voltage ripple using Equation 5-17:
3.
Table 2-2 summarizes the typical value of components
for particular input and output voltage, and 600 kHz
switching frequency design.
5.7
1
= V IN K div D 1 – D ----------------f SW
EQUATION 5-15:
R1 R11 K div = ------------------------------------R inj + R1 R11
Where:
VIN
Power Stage Input Voltage
D
Duty Cycle
fSW
Switching Frequency
(R1||R11||Rinj) x Cff
In Equation 5-14 and Equation 5-15, it is assumed that
the time constant associated with Cff must be much
greater than the switching period:
EQUATION 5-16:
1 - = T
------------------ « 1
f SW
If the voltage divider resistors R1 and R11 are in the kΩ
range, then a Cff of 1 nF to 100 nF can easily satisfy the
large time constant requirements. Also, a 100 nF
injection capacitor Cinj is used in order to be considered
as short for a wide range of the frequencies.
The process of sizing the ripple injection resistor and
capacitors is:
2017 Microchip Technology Inc.
Select Cinj as 100 nF, which could be considered
as short for a wide range of the frequencies.
Thermal Measurements and Safe
Operating Area
Measuring the IC’s case temperature is recommended
to ensure it is within its operating limits. Although this
may seem like a very elementary task, it is easy to get
erroneous results. The most common mistake is to use
the standard thermal couple that comes with a thermal
meter. This thermal couple wire gauge is large, typically
22-gauge, and behaves like a heat sink, resulting in a
lower case measurement.
Two methods of temperature measurement use a
smaller thermal couple wire or an infrared
thermometer. If a thermal couple wire is used, it must
be constructed of 36-gauge wire or higher (smaller wire
size) to minimize the wire heat-sinking effect. In
addition, the thermal couple tip must be covered in
either thermal grease or thermal glue to make sure that
the thermal couple junction makes good contact with
the case of the IC. Omega brand thermal couple
(5SC-TT-K-36-36) is adequate for most applications.
Wherever possible, an infrared thermometer is
recommended. The measurement spot size of most
infrared thermometers is too large for an accurate
reading on small form factor ICs.
However, an IR thermometer from Optris has a 1 mm
spot size, which makes it a good choice for measuring
the hottest point on the case. An optional stand makes
it easy to hold the beam on the IC for long periods of
time.
DS20005464B-page 27
MIC28303
The safe operating area (SOA) of the MIC28303 is
shown in the first three graphs of the Typical
Characteristics section. These thermal measurements
were taken on the MIC28303 evaluation board.
Because the MIC28303 is an entire system comprised
of switching regulator controller, MOSFETs and
inductor, the part needs to be considered a system.
The SOA curves will provide guidance for reasonable
use of the MIC28303.
5.8
Emission Characteristics of
MIC28303
The MIC28303 integrates switching components in a
single package, so the MIC28303 has reduced
emission compared to a standard buck regulator with
external MOSFETS and inductors. The radiated EMI
scans for MIC28303 are shown in Section 2.0, Typical
Performance Curves. The limit on the graph is per
EN55022 Class B standard.
DS20005464B-page 28
2017 Microchip Technology Inc.
MIC28303
6.0
PCB LAYOUT GUIDELINES
To minimize EMI and output noise, follow these layout
recommendations.
PCB layout is critical to achieve reliable, stable and
efficient performance. A ground plane is required to
control EMI and minimize the inductance in power,
signal and return paths.
The following figures optimized from small form factor
point of view show top and bottom layers of a four-layer
PCB. It is recommended to use mid-layer 1 as a
continuous ground plane.
The following guidelines should be followed to ensure
proper operation of the MIC28303 converter:
6.1
6.3
RC Snubber
• Place the RC snubber on the same side of the
board and as close to the SW pin as possible.
IC
• The analog ground pin (GND) must be connected
directly to the ground planes. Do not route the
GND pin to the PGND pin on the top layer.
• Place the IC close to the point-of-load (POL).
• Use fat traces to route the input and output power
lines.
• Analog and power grounds should be kept
separate and connected at only one location.
6.2
• Do not replace the ceramic input capacitor with
any other type of capacitor. Any type of capacitor
can be placed in parallel with the input capacitor.
• If a Tantalum input capacitor is placed in parallel
with the input capacitor, it must be recommended
for switching regulator applications and the
operating voltage must be derated by 50%.
• In “Hot-Plug” applications, a Tantalum or
Electrolytic bypass capacitor must be used to limit
the over-voltage spike seen on the input supply
with power is suddenly applied.
Input Capacitor
• Place the input capacitors on the same side of the
board and as close to the IC as possible.
• Place several vias to the ground plane close to
the input capacitor ground terminal.
• Use either X7R or X5R dielectric input capacitors.
Do not use Y5V or Z5U type capacitors.
FIGURE 6-1:
6.4
SW Node
• Do not route any digital lines underneath or close
to the SW node.
• Keep the switch node (SW) away from the
feedback (FB) pin.
6.5
Output Capacitor
• Use a wide trace to connect the output capacitor
ground terminal to the input capacitor ground
terminal.
• Phase margin will change as the output capacitor
value and ESR changes.
• The feedback trace should be separate from the
power trace and connected as close as possible
to the output capacitor. Sensing a long
high-current load trace can degrade the DC load
regulation.
Top and Bottom Layer of a Four-Layer Board.
2017 Microchip Technology Inc.
DS20005464B-page 29
MIC28303
7.0
PACKAGING INFORMATION
64-Lead H3QFN 12 mm x 12 mm Package
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
DS20005464B-page 30
2017 Microchip Technology Inc.
MIC28303
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
2017 Microchip Technology Inc.
DS20005464B-page 31
MIC28303
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging
DS20005464B-page 32
2017 Microchip Technology Inc.
MIC28303
APPENDIX A:
REVISION HISTORY
Revision B (October 2017)
• Minor text changes throughout.
Revision A (June 2016)
• Converted Micrel document MIC28303 to Microchip
data sheet.
• Minor text changes throughout.
2017 Microchip Technology Inc.
DS2005464B-page 33
MIC28303
NOTES:
DS2005464B-page 34
2017 Microchip Technology Inc.
MIC28303
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, contact your local Microchip representative or sales office.
PART NO.
-X
X
XX
Examples:
a)
MIC28303-1YMP:
b)
MIC28303-2YMP:
Device Features Temperature Package
Device:
MIC28303:
Features:
1
2
=
=
Temperature:
Y
=
Package:
MP =
50V, 3A Power Module
HyperLight Load
Hyper Speed Control
50V 3A Power Module,
HyperLight Load,
–40°C to +125°C junction
temperature range,
64LD QFN
50V 3A Power Module,
Hyper Speed Control,
–40°C to +125°C junction
temperature range,
64LD QFN
–40°C to +125°C
64-Pin 12 mm x 12 mm QFN
2017 Microchip Technology Inc.
DS20005464B-page 35
MIC28303
NOTES:
DS20005464B-page 36
2017 Microchip Technology Inc.
Note the following details of the code protection feature on Microchip devices:
•
Microchip products meet the specification contained in their particular Microchip Data Sheet.
•
Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the
intended manner and under normal conditions.
•
There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our
knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data
Sheets. Most likely, the person doing so is engaged in theft of intellectual property.
•
Microchip is willing to work with the customer who is concerned about the integrity of their code.
•
Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not
mean that we are guaranteeing the product as “unbreakable.”
Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our
products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts
allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act.
Information contained in this publication regarding device
applications and the like is provided only for your convenience
and may be superseded by updates. It is your responsibility to
ensure that your application meets with your specifications.
MICROCHIP MAKES NO REPRESENTATIONS OR
WARRANTIES OF ANY KIND WHETHER EXPRESS OR
IMPLIED, WRITTEN OR ORAL, STATUTORY OR
OTHERWISE, RELATED TO THE INFORMATION,
INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR
FITNESS FOR PURPOSE. Microchip disclaims all liability
arising from this information and its use. Use of Microchip
devices in life support and/or safety applications is entirely at
the buyer’s risk, and the buyer agrees to defend, indemnify and
hold harmless Microchip from any and all damages, claims,
suits, or expenses resulting from such use. No licenses are
conveyed, implicitly or otherwise, under any Microchip
intellectual property rights unless otherwise stated.
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile memory and
analog products. In addition, Microchip’s quality system for the design
and manufacture of development systems is ISO 9001:2000 certified.
QUALITY MANAGEMENT SYSTEM
CERTIFIED BY DNV
Trademarks
The Microchip name and logo, the Microchip logo, AnyRate, AVR,
AVR logo, AVR Freaks, BeaconThings, BitCloud, CryptoMemory,
CryptoRF, dsPIC, FlashFlex, flexPWR, Heldo, JukeBlox, KEELOQ,
KEELOQ logo, Kleer, LANCheck, LINK MD, maXStylus,
maXTouch, MediaLB, megaAVR, MOST, MOST logo, MPLAB,
OptoLyzer, PIC, picoPower, PICSTART, PIC32 logo, Prochip
Designer, QTouch, RightTouch, SAM-BA, SpyNIC, SST, SST
Logo, SuperFlash, tinyAVR, UNI/O, and XMEGA are registered
trademarks of Microchip Technology Incorporated in the U.S.A.
and other countries.
ClockWorks, The Embedded Control Solutions Company,
EtherSynch, Hyper Speed Control, HyperLight Load, IntelliMOS,
mTouch, Precision Edge, and Quiet-Wire are registered
trademarks of Microchip Technology Incorporated in the U.S.A.
Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any
Capacitor, AnyIn, AnyOut, BodyCom, chipKIT, chipKIT logo,
CodeGuard, CryptoAuthentication, CryptoCompanion,
CryptoController, dsPICDEM, dsPICDEM.net, Dynamic Average
Matching, DAM, ECAN, EtherGREEN, In-Circuit Serial
Programming, ICSP, Inter-Chip Connectivity, JitterBlocker,
KleerNet, KleerNet logo, Mindi, MiWi, motorBench, MPASM, MPF,
MPLAB Certified logo, MPLIB, MPLINK, MultiTRAK, NetDetach,
Omniscient Code Generation, PICDEM, PICDEM.net, PICkit,
PICtail, PureSilicon, QMatrix, RightTouch logo, REAL ICE, Ripple
Blocker, SAM-ICE, Serial Quad I/O, SMART-I.S., SQI,
SuperSwitcher, SuperSwitcher II, Total Endurance, TSHARC,
USBCheck, VariSense, ViewSpan, WiperLock, Wireless DNA, and
ZENA are trademarks of Microchip Technology Incorporated in the
U.S.A. and other countries.
SQTP is a service mark of Microchip Technology Incorporated in
the U.S.A.
Silicon Storage Technology is a registered trademark of Microchip
Technology Inc. in other countries.
GestIC is a registered trademark of Microchip Technology
Germany II GmbH & Co. KG, a subsidiary of Microchip Technology
Inc., in other countries.
All other trademarks mentioned herein are property of their
respective companies.
© 2017, Microchip Technology Incorporated, All Rights Reserved.
ISBN: 978-1-5224-2260-0
== ISO/TS 16949 ==
2017 Microchip Technology Inc.
DS20005464B-page 37
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DS20005878A-page 30
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10/10/17
