MIC22602
1 MHz, 6A Integrated Switch High Efficiency Synchronous Buck Regulator
Features
General Description
•
•
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The MIC22602 is a high efficiency 6A Integrated switch
synchronous buck (step-down) regulator. The
MIC22602 is optimized for highest efficiency, achieving
more than 95% efficiency while still switching at 1MHz
over a broad range. The device works with a small 1μH
inductor and 100 μF output capacitor. The ultra-high
speed control loop keeps the output voltage within
regulation even under extreme transient load swings
commonly found in FPGAs and low voltage ASICs. The
output voltage can be adjusted down to 0.7V to
address all low voltage power needs. The MIC22602
offers a full range of sequencing and tracking options.
The EN/DLY pin combined with the Power Good/POR
pin allows multiple outputs to be sequenced in any way
during turn-on and turn-off. The RC (Ramp Control) pin
allows the device to be connected to another product in
the MIC22xxx and/or MIC68xxx family, to keep the
output voltages within a certain ∆V on start up.
Package Type
PGND
SW
MIC22602
24-Lead 4 mm x 4 mm QFN (ML)
(Top View)
SW
High Power Density Point-of-Load Conversion
Servers and Routers
Blu-Ray/DVD Players and Recorders
Computing Peripherals
Base Stations
FPGAs, DSP, and Low Voltage ASIC Power
PGND
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The MIC22602 is available in a 24-pin 4 mm x 4 mm
QFN with a junction operating range from –40°C to
+125°C.
SW
Applications
SW
•
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Input Voltage Range: 2.6V to 5.5V
Output Voltage Adjustable Down to 0.7V
Output Current Up to 6A
Full Sequencing and Tracking Ability
Power-on-Reset/Power Good Output
Efficiency >95% Across a Broad Load Range
Ultra-Fast Transient Response, Easy RC
Compensation
100% Maximum Duty Cycle
Fully Integrated MOSFET Switches
Hiccup Mode Current Limiting
Micropower Shutdown
Thermal Shutdown and Current-Limit Protection
24-Pin 4 mm x 4 mm QFN
–40°C to +125°C Junction Temperature Range
PVIN
PVIN
EN/DLY
SVIN
DELAY
SGND
EP
RC
COMP
FB
POR/PG
PVIN
2020 Microchip Technology Inc.
PGND
SW
SW
SW
SW
PGND
PVIN
DS20006300A-page 1
MIC22602
Typical Application Circuit
MIC22602
Functional Block Diagram
DS20006300A-page 2
2020 Microchip Technology Inc.
MIC22602
1.0
ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings †
Supply Voltage (PVIN, SVIN)......................................................................................................................... –0.3V to +6V
Output Switch Voltage (VSW) ....................................................................................................................... –0.3V to +6V
Output Switch Current (ISW)...................................................................................................................Internally Limited
Logic Input Voltage (EN, POR, DLY)............................................................................................................. –0.3V to VIN
Control Voltage (RC, COMP, FB) .................................................................................................................. –0.3V to VIN
Storage Temperature (TS) ......................................................................................................................–65°C to +150°C
ESD Rating (Note 1) ..................................................................................................................................................2 kV
Lead Temperature (Soldering 10 sec.).................................................................................................................... 260°C
Operating Ratings ††
Supply Voltage (VIN) ................................................................................................................................. +2.6V to +5.5V
Junction Temperature (TJ)............................................................................................................... –40°C ≤ TJ ≤ +125°C
Thermal Resistance
4 mm x 4 mm MLF-24 (θJC) ................................................................................................................................. 14°C/W
4 mm x 4 mm MLF-24 (θJA .................................................................................................................................. 40°C/W
† 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 recommended.
ELECTRICAL CHARACTERISTICS
Electrical Characteristics: TA = +25°C with VIN = VEN = 3.3V; VOUT = 1.8V, unless otherwise specified. Bold values
indicate –40°C≤ TJ ≤ +125°C. Note 1
Parameter
Symbol
Min.
Typ.
Max.
Units
Supply Voltage Range
—
2.6
—
5.5
V
—
VIN Turn-ON Voltage Threshold
—
2.4
2.5
2.6
V
VIN Rising
UVLO Hysteresis
—
—
280
—
mV
—
Quiescent Current, PWM Mode
—
—
850
1300
μA
VEN ≥ 1.34V; VFB = 0.9V (not
switching)
Shutdown Current
ISHDN
—
5
10
μA
VEN = 0V
Feedback Voltage
VFB
0.686
0.7
0.714
V
±2% (over temperature)
—
—
1
—
nA
—
ILIM
6
10
14
A
VFB = 0.5
Output Voltage Line Regulation
—
—
0.2
—
%
VOUT = 1.8V, VIN = 2.6 to 5.5V,
ILOAD = 100 mA
Output Voltage Load Regulation
—
—
0.2
—
%
100 mA < ILOAD < 6A, VIN = 3.3V
Maximum Duty Cycle
—
100
—
—
%
VFB ≤ 0.5V
Switch ON-Resistance PFET
—
—
0.03
—
Ω
ISW = 1000 mA; VFB = 0.5V
Switch ON-Resistance NFET
—
—
0.025
—
Ω
ISW = 1000 mA; VFB = 0.9V
FB Pin Input Current
Current Limit
Note 1:
Conditions
Specification for packaged product only.
2020 Microchip Technology Inc.
DS20006300A-page 3
MIC22602
ELECTRICAL CHARACTERISTICS (CONTINUED)
Electrical Characteristics: TA = +25°C with VIN = VEN = 3.3V; VOUT = 1.8V, unless otherwise specified. Bold values
indicate –40°C≤ TJ ≤ +125°C. Note 1
Parameter
Symbol
Min.
Typ.
Max.
Units
Conditions
Oscillator Frequency
fO
0.8
1
1.2
MHz
—
EN Threshold Voltage
—
1.14
1.24
1.34
V
—
EN Source Current
—
0.6
1
1.8
μA
VIN = 2.6V to 5.5V
RC Pin Current
IRAMP
0.5
1
1.7
μA
Ramp Control current
Power-on-Reset
IPG(LEAK)
—
—
1
μA
—
—
2
μA
Power-on-Reset
VPG(LO)
—
130
—
mV
Power-on-Reset
VPG
7.5
10
12.5
%
Threshold,% of VOUT below
nominal
—
2
—
%
Hysteresis
VPORH = 5.5V; POR = High
Output Logic Low Voltage
(undervoltage condition),
IPOR = 5 mA
Overtemperature Shutdown
—
—
160
—
°C
—
Overtemperature Shutdown
Hysteresis
—
—
20
—
°C
—
Note 1:
Specification for packaged product only.
TEMPERATURE SPECIFICATIONS
Parameters
Symbol
Min.
Typ.
Max.
Units
Conditions
Junction Temperature Range
TJ
–40
—
+125
°C
Storage Temperature Range
TS
–65
—
+150
°C
—
Lead Temperature
—
—
+260
—
°C
Soldering, 10 sec.
θJC
—
14
—
°C/W
—
θJA
—
40
—
°C/W
—
Temperature Ranges
—
Package Thermal Resistance
Thermal Resistance, QFN 24-Lead
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.
DS20006300A-page 4
2020 Microchip Technology Inc.
MIC22602
TYPICAL PERFORMANCE CURVES
Note:
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.
SHUTDOWN CURRENT (μA)
10
0.701
EN = 0V
V = 3.3V
FEEDBACK VOLTAGE (V)
2.0
IN
8
6
4
2
0.700
0.699
0.698
0.697
0.696
= 3.3V
IN
-40
-25
-10
5
20
35
50
65
80
95
110
125
-40
-25
-10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
TEMPERATURE (°C)
FIGURE 2-1:
Temperature
Shutdown Current vs.‘
EN > 1.34V
V = 0.9V
FB
V
IN
ENABLE VOLTAGE (V)
900
890
880
870
860
850
840
830
820
810
800
FIGURE 2-4:
Temperature.
= 3.3V
No Switching
Feedback Voltage vs.
1.245
V = 3.3V
1.244 IN
1.243
1.242
1.241
1.24
1.239
1.238
1.237
1.236
1.235
-40
-25
-10
5
20
35
50
65
80
95
110
125
-40
-25
-10
5
20
35
50
65
80
95
110
125
QUIESCENT CURRENT (μA)
IN
0.695
0
TEMPERATURE (°C)
TEMPERATURE (C)
Quiescent Current vs.
0.6981
0.6980
2.5
FIGURE 2-3:
Voltage.
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
ENABLE HYSTERESIS (V)
0.6990
EN = VIN
0.6989
V = 3.3V
0.6988 IN
AMB = 25°C
0.6987
0.6986
0.6985
0.6984
0.6983
0.6982
Enable Voltage vs.
0.0100
V = 3.3V
0.0095 IN
0.0090
0.0085
0.0080
0.0075
0.0070
0.0065
0.0060
0.0055
0.0050
5.5
Feedback Voltage vs. Input
2020 Microchip Technology Inc.
FIGURE 2-5:
Temperature.
-40
-25
-10
5
20
35
50
65
80
95
110
125
FIGURE 2-2:
Temperature.
FEEDBACK VOLTAGE (V)
V
EN = V
TEMPERATURE (°C)
FIGURE 2-6:
Temperature.
Enable Hysteresis vs.
DS20006300A-page 5
MIC22602
FREQUENCY (kHz)
1015
1010
1200
VIN = 3.3V
QUIESCENT CURRENT (μA)
1020
EN = VIN
1005
1000
995
990
985
-40
-25
-10
5
20
35
50
65
80
95
110
125
980
1100
EN > 1.34V
VFB = 0.9V
No Switching
1000
900
800
700
600
2.5
TEMPERATURE (°C)
FIGURE 2-7:
Frequency vs. Temperature.
FIGURE 2-10:
Voltage.
1040
7.0
SHUTDOWN CURRENT (μA)
FREQUENCY (kHz)
EN = VIN
1030
1020
1010
1000
990
980
2.5
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
FIGURE 2-8:
5.5
Frequency vs. Input Voltage.
RDSON (mOhm)
40
EN = VIN
38
5.5
Quiescent Current vs. Input
EN = 0V
6.5
6.0
5.5
5.0
4.5
4.0
2.5
FIGURE 2-11:
Voltage.
100
95
36
90
34
32
30
28
85
80
75
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
5.5
Shutdown Current vs. Input
2.6VIN
3.3VIN
5.5VIN
70
65
60
26
24
22
20
2.5
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
3
3.5
4
4.5
5
INPUT VOLTAGE (V)
FIGURE 2-9:
Voltage.
DS20006300A-page 6
5.5
P-Channel RDS(ON) vs. Input
55
50
0
FIGURE 2-12:
1
2
3
4
5
OUTPUT CURRENT (A)
6
Efficiency @ 1.2VOUT.
2020 Microchip Technology Inc.
MIC22602
100
95
90
85
80
100
80
60
40
20
3.3VIN
5.5VIN
2.6VIN
75
0
70
65
60
-20
-40
-60
-80
55
50
0
FIGURE 2-13:
1
2
3
4
5
OUTPUT CURRENT (A)
6
Efficiency @ 1.8VOUT.
100
95
90
85
80
75
70
65
60
55
VIN = 5.5V
50
0
1
2
3
4
5
OUTPUT CURRENT (A)
FIGURE 2-14:
6
Efficiency @ 3.3VOUT.
100
80
60
250
200
150
40
20
0
-20
-40
-60
-80
100
50
0
-50
-100
-150
-100
100
FIGURE 2-15:
1.8V).
-100
100
FIGURE 2-16:
1.8V).
250
200
150
100
50
0
-50
-100
-150
-200
1k
10k
100k
FREQUENCY (Hz)
-250
1M
Bode Plot (VIN = 5.5V, VO =
100
80
250
200
60
40
150
100
20
0
-20
-40
-60
50
0
-50
-100
-150
-80
-100
100
FIGURE 2-17:
3.3V).
1k
10k
100k
FREQUENCY (Hz)
-200
-250
1M
Bode Plot (VIN = 5.0V, VO =
-200
1k
10k
100k
FREQUENCY (Hz)
-250
1M
Bode Plot (VIN = 3.6V, VO =
2020 Microchip Technology Inc.
DS20006300A-page 7
MIC22602
FIGURE 2-18:
10 nF).
Start-Up/Shutdown (CRC =
FIGURE 2-21:
Switching Waveforms.
FIGURE 2-19:
Start-Up (CRC = 0 nF).
FIGURE 2-22:
Transient Response.
FIGURE 2-20:
High DC Operation.
FIGURE 2-23:
Transient Response.
DS20006300A-page 8
2020 Microchip Technology Inc.
MIC22602
FIGURE 2-24:
Behavior.
Hiccup Current Limit
FIGURE 2-25:
Start-Up Into Short.
2020 Microchip Technology Inc.
DS20006300A-page 9
MIC22602
3.0
PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1:
PIN FUNCTION TABLE
Pin Number
Pin Name
Description
1, 6, 13, 18
PVIN
Power Supply Voltage (Input): Requires bypass capacitor to GND.
17
SVIN
Signal Power Supply Voltage (Input): Requires bypass capacitor to GND.
2
EN
Enable/Delay (Input): When this pin is pulled higher than the enable threshold, the part
will start up. Below this voltage, the device is in its low quiescent current mode. The pin
has a 1 μA current source charging it to VIN. By adding a capacitor to this pin, a delay
may easily be generated. The enable function will not operate with an input voltage
lower than the min specified.
4
RC
Ramp Control: A capacitor-to-ground from this pin determines the slew rate of the output voltage during start-up. This can be used for tracking capability as well as soft start.
The RC pin cannot be left floating. Use a minimum capacitor value of 470 pF or larger.
14
FB
Feedback: Input to the error amplifier. Connect to the external resistor divider network
to set the output voltage.
15
COMP
Compensation pin (Input): Place a RC network to GND to compensate the device, see
Section 5.0 “Application Information”.
5
POR/PG
Power-on-Reset (Output): Open-drain output device indicates when the output is out of
regulation and is active after the delay set by the DELAY pin.
7, 12, 19, 24
PGND
Power Ground (Signal): Ground
16
SGND
Signal Ground (Signal): Ground
3
DELAY
Delay (Input): Capacitor to ground sets internal delay timer. Timer delays power-on
reset (POR) output at turn-on and ramp down at turn-off.
8, 9, 10, 11,
20, 21, 22, 23
SW
EP
GND
DS20006300A-page 10
Switch (Output): Internal power MOSFET output switches.
Exposed Pad (Power): Must make a full connection to a GND plane for full output
power to be realized.
2020 Microchip Technology Inc.
MIC22602
4.0
FUNCTIONAL DESCRIPTION
4.1
PVIN, SVIN
PVIN is the input supply to the internal 30 mΩ
P-channel Power MOSFET. This should be connected
externally to the SVIN pin. The supply voltage range is
from 2.6V to 5.5V. A 22 μF ceramic is recommended
for bypassing each PVIN supply.
4.2
EN/DLY
This pin is internally fed with a 1 μA current source from
VIN. A delayed turn on is implemented by adding a
capacitor to this pin. The delay is proportional to the
capacitor value. The internal circuits are held off until
EN/DLY reaches the enable threshold of 1.24V.
4.3
RC
RC allows the slew rate of the output voltage to be
programmed by the addition of a capacitor from RC to
ground. RC is internally fed with a 1 μA current source
and VOUT slew rate is proportional to the capacitor and
the 1 μA source. The RC pin cannot be left floating.
Use a minimum capacitor value of 470 pF or larger.
4.4
voltage and after the delay set by CDELAY. POR is
asserted low without delay when enable is set low or
when the output goes below the –10% threshold. For a
Power Good (PG) function, the delay can be set to a
minimum. This can be done by removing the DELAY
capacitor.
4.8
SW
This is the connection to the drain of the internal
P-Channel MOSFET and drain of the N-Channel
MOSFET. This is a high frequency high power
connection; therefore traces should be kept as short
and as wide as practical.
4.9
SGND
Internal signal ground for all low power sections.
4.10
PGND
Internal ground connection to the source of the internal
N-channel MOSFETs.
DELAY
Adding a capacitor to this pin allows the delay of the
POR signal.
When VOUT reaches 90% of its nominal voltage, the
DELAY pin current source (1 μA) starts to charge the
external capacitor. At 1.24V, POR is asserted high.
4.5
COMP
The MIC22602 uses an internal compensation network
containing a fixed frequency zero (phase lead
response) and pole (phase lag response) that allows
the external compensation network to be simplified for
stability. The addition of a single capacitor and resistor
will add the necessary pole and zero for voltage mode
loop stability using low value, low ESR ceramic
capacitors.
4.6
FB
The feedback pin provides the control path to control
the output. A resistor divider connecting the feedback
to the output is used to adjust the desired output
voltage. Refer to Section 5.7 “Feedback” in
Section 5.0 “Application Information” for more
detail.
4.7
POR
This is an open-drain output. A 47.5 kΩ resistor can be
used for a pull-up to this pin. POR is asserted high
when output voltage reaches 90% of nominal set
2020 Microchip Technology Inc.
DS20006300A-page 11
MIC22602
5.0
APPLICATION INFORMATION
The MIC22602 is a 6A synchronous step-down
regulator IC with a fixed 1 MHz, voltage mode PWM
control scheme. The other features include tracking
and sequencing control for controlling multiple output
power systems, power-on-reset.
5.1
Input Capacitor
A minimum 22 μF ceramic is recommended on each of
the PVIN pins for bypassing. X5R or X7R dielectrics
are recommended for the input capacitor. Y5V
dielectric is not recommended.
5.2
Output Capacitor
The MIC22602 was designed specifically for the use of
ceramic output capacitors. Additional 100 μF can
improve transient performance. Because the
MIC22602 is voltage mode, the control loop relies on
the inductor and output capacitor for compensation.
For this reason, do not use excessively large output
capacitors. The output capacitor requires either an X7R
or X5R dielectric. Y5V and Z5U dielectric capacitors,
aside from the undesirable effect of their wide variation
in capacitance over temperature, become resistive at
high frequencies. Using Y5V or Z5U capacitors can
cause instability in the MIC22602.
5.3
Inductor Selection
Inductor selection will be determined by the following
(not necessarily in the order of importance):
•
•
•
•
Inductance
Rated current value
Size requirements
DC resistance (DCR)
The MIC22602 is designed to use a 0.47 μH to 4.7 μH
inductor.
Maximum current ratings of the inductor are generally
given in two methods: permissible DC current and
saturation current. Permissible DC current can be rated
either for a 40°C temperature rise or a 10% loss in
inductance. Ensure the inductor selected can handle
the maximum operating current. When saturation
current is specified, make sure that there is enough
margin that the peak current will not saturate the
inductor. The ripple can add as much as 1.2A to the
output current level. The RMS rating should be chosen
to be equal or greater than the current limit of the
MIC22602 to prevent overheating in a fault condition.
For best electrical performance, the inductor should be
placed very close to the SW nodes of the IC. It is
important to test all operating limits before settling on
the final inductor choice.
DS20006300A-page 12
The size requirements refer to the area and height
requirements that are necessary to fit a particular
design. Please refer to the inductor dimensions on their
data sheet.
DC resistance is also important. While DCR is inversely
proportional to size, DCR can represent a significant
efficiency loss. Refer to the Efficiency Considerations
section for a more detailed description.
5.4
EN/DLY Capacitor
EN/DLY sources 1 μA out of the IC to allow a startup
delay to be implemented. The delay time is simply the
time it takes 1 μA to charge CDLY to 1.24V. Therefore:
EQUATION 5-1:
1.24 C DLY
t DLY = -----------------------------–6
1.10
5.5
Efficiency Considerations
Efficiency is defined as the amount of useful output
power, divided by the amount of power consumed.
EQUATION 5-2:
V OUT I OUT
Efficiency % = --------------------------------- 100
V I
IN
IN
Maintaining high efficiency serves two purposes. It
decreases power dissipation in the power supply,
reducing the need for heat sinks and thermal design
considerations and it decreases consumption of
current for battery powered applications. Reduced
current drawn from a battery increases the devices
operating time, particularly in hand-held devices.
There are mainly two loss terms in switching
converters: conduction losses and switching losses.
Conduction losses are simply the power losses due to
VI or I2R. For example, power is dissipated in the high
side switch during the on cycle. The power loss is equal
to the high-side MOSFET RDS(ON) multiplied by the
RMS Switch Current squared (ISW2). During the off
cycle, the low-side N-Channel MOSFET conducts, also
dissipating power. Similarly, the inductor’s DCR and
capacitor’s ESR also contribute to the I2R losses.
Device operating current also reduces efficiency by the
product of the quiescent (operating) current and the
supply voltage. The power consumed for switching at
1 MHz frequency and power loss due to switching
transitions add up to switching losses.
2020 Microchip Technology Inc.
MIC22602
Figure 5-1 shows an efficiency curve. In the portion
from 0A to 1A, efficiency losses are dominated by
quiescent current losses, gate drive, and transition
losses. In this case, lower supply voltages yield greater
efficiency in that they require less current to drive the
MOSFETs and have reduced input power
consumption.
100
Alternatively, under lighter loads, the ripple current
becomes a significant factor. When light load
efficiencies become more critical, a larger inductor
value maybe desired. Larger inductance reduces the
peak-to-peak inductor ripple current, which minimize
losses. The following graph in Figure 3 illustrates the
effects of inductance value at light load.
95
VIN = 3.3V
VOUT = 1.8V
95
90
90
85
85
80
75
75
70
65
70
60
60
55
55
50
0
FIGURE 5-1:
L = 1μH
80
L = 4.7μH
65
1
2
3
4
5
LOAD CURRENT (A)
Efficiency Curve.
The region, 1A to 6A, efficiency loss is dominated by
MOSFET RDS(ON) and inductor DC losses. Higher
input supply voltages will increase the Gate-to-Source
voltage on the internal MOSFETs, reducing the internal
RDS(ON). This improves efficiency by decreasing
conduction loss in the device but the inductor loss is
inherent to the converter. In which case, inductor
selection becomes increasingly critical in efficiency
calculations. As the inductors are reduced in size, the
DC resistance (DCR) can become quite significant.
The DCR losses can be calculated as follows:
EQUATION 5-3:
2
L PD = I OUT DCR
From that, the loss in efficiency due to inductor
resistance can be calculated as in Equation 5-4.
EQUATION 5-4:
V OUT I OUT
EL = 1 – ------------------------------------------------------- 100
V
I
+L
OUT
OUT
50
0
6
PD
Where:
EL = Efficiency loss value in percent.
FIGURE 5-2:
5.6
200
400
600
800
OUTPUT CURRENT (mA)
Efficiency vs. Inductance.
Compensation
The MIC22602 has a combination of internal and
external stability compensation to simplify the circuit for
small, high efficiency designs. In such designs, voltage
mode conversion is often the optimum solution. Voltage
mode is achieved by creating an internal 1 MHz ramp
signal and using the output of the error amplifier to
modulate the pulse width of the switch node,
maintaining output voltage regulation. With a typical
gain bandwidth of 100 kHz to 200 kHz, the MIC22602
is capable of extremely fast transient responses.
The MIC22602 is designed to be stable with a typical
application using a 1 μH inductor and a 100 μF ceramic
(X5R) output capacitor. These values can be varied
dependent on the trade off between size, cost and
efficiency, keeping the LC natural frequency ideally
less than 26 kHz to ensure stability can be achieved.
The minimum recommended inductor value is 0.47 μH
and minimum recommended output capacitor value is
22 μF. With a larger inductor, there is a reduced
peak-to-peak current which yields a greater efficiency
at lighter loads. A larger output capacitor will improve
transient response by providing a larger hold up
reservoir of energy to the output.
The integration of one pole-zero pair within the control
loop greatly simplifies compensation. The optimum
values for CCOMP (in series with a 20 kΩ resistor) are
shown in Table 5-1.
Efficiency loss due to DCR is minimal at light loads and
gains significance as the load is increased. Inductor
selection becomes a trade-off between efficiency and
size in this case.
2020 Microchip Technology Inc.
DS20006300A-page 13
MIC22602
TABLE 5-1:
COMPENSATION CAPACITOR
SELECTION
C
L
22 μF 47 μF
47 μF 100 μF
100 μF 470 μF
0.47 μH
0 pF - 10 pF
(Note 1)
22 pF
33 pF
1 μH
0 pF - 15 pF
(Note 2)
15 pF 22 pF
33 pF
2.2 μH
15 pF 33 pF
33 pF 47 pF
100 pF 220 pF
Note 1:
2:
VOUT > 1.2V
VOUT > 1V
5.7
PWM control provides fixed-frequency operation. By
maintaining a constant switching frequency,
predictable fundamental and harmonic frequencies are
achieved.
5.9
Feedback
EQUATION 5-5:
R1
R2 = ----------------------------V
OUT
--------------- – 1
V
REF
Where:
VREF = 0.7V
VOUT = The desired output voltage.
A 10 kΩ or lower resistor value from the output to the
feedback is recommended because large feedback
resistor values increase the impedance at the feedback
pin, making the feedback node more susceptible to
noise pick-up. A small capacitor (50 pF to 100 pF)
across the lower resistor can reduce noise pick-up by
providing a low impedance path to ground.
PWM Operation
The MIC22602 is a voltage mode, pulse width
modulation (PWM) controller. By controlling the duty
cycle, a regulated DC output voltage is achieved. As
load or supply voltage changes, so does the duty cycle
to maintain a constant output voltage. In cases where
the input supply runs into a dropout condition, the
MIC22602 will run at 100% duty cycle.
Sequencing and Tracking
The MIC22602 provides additional pins to provide
up/down sequencing and tracking capability for
connecting multiple voltage regulators together.
5.9.1
The MIC22602 provides a feedback pin to adjust the
output voltage to the desired level. This pin connects
internally to an error amplifier. The error amplifier then
compares the voltage at the feedback to the internal
0.7V reference voltage and adjusts the output voltage
to maintain regulation. The resistor divider network for
a desired VOUT is given by:
5.8
Because the low-side N-Channel MOSFET provides
the current during the off cycle, very low power is
dissipated during the off period.
EN/DLY PIN
The EN pin contains a trimmed, 1 μA current source
that can be used with a capacitor to implement a fixed
desired delay in some sequenced power systems. The
threshold level for power on is 1.24V with a hysteresis
of 20 mV.
5.9.2
DELAY PIN
The DELAY pin also has a 1 μA trimmed current source
and a 1 μA current sink which acts with an external
capacitor to delay the operation of the Power-on-Reset
(POR) output. This can be used also in sequencing
outputs in a sequenced system, but with the addition of
a conditional delay between supplies; allowing a first
up, last down power sequence.
After EN is driven high, VOUT will start to rise (rate
determined by RC capacitor). As the FB voltage goes
above 90% of its nominal set voltage, DELAY begins to
rise as the 1μA source charges the external capacitor.
When the threshold of 1.24V is crossed, POR is
asserted high and DELAY continues to charge to a
voltage SVIN. When FB falls below 90% of nominal,
POR is asserted low immediately. However, if EN is
driven low, POR will fall immediately to the low state
and DELAY will begin to fall as the external capacitor is
discharged by the 1 μA current sink. When the
threshold of (VTP + 1.24V) – 1.24V is crossed (VTP is
the internal voltage clamp VTP ~ 0.9V), VOUT will begin
to fall at a rate determined by the RC capacitor. As the
voltage change in both cases is 1.24V, both rising and
falling delays are matched at:
EQUATION 5-6:
1.24 C DLY
t POR = -----------------------------–6
1.10
The MIC22602 provides constant switching at 1 MHz
with synchronous internal MOSFETs. The internal
MOSFETs include a high-side P-Channel MOSFET
from the input supply to the switch pin and an
N-Channel MOSFET from the switch pin-to-ground.
DS20006300A-page 14
2020 Microchip Technology Inc.
MIC22602
5.9.3
RC PIN
The RC pin provides a trimmed 1 μA current
source/sink similar to the DELAY pin for accurate
ramp-up (soft-start) and ramp-down control. This
allows the MIC22602 to be used in systems requiring
voltage tracking or ratio-metric voltage tracking at
startup.
There are two ways of using the RC pin:
• Externally driven from a voltage source
• Externally attached capacitor sets output ramp
up/down rate
In the first case, driving RC with a voltage from 0V to
VREF programs the output voltage between 0% and
100% of the nominal set voltage.
In the second case, the external capacitor sets the
ramp up and ramp down time of the output voltage. The
time is given by:
EQUATION 5-7:
0.7 C RC
t RAMP = -----------------------–6
1.10
Where:
tRAMP = The time from 0% to 100% nominal output
voltage.
The RC pin cannot be left floating. Use a minimum
capacitor value of 470 pF or larger.
2020 Microchip Technology Inc.
DS20006300A-page 15
MIC22602
5.9.4
SEQUENCING AND TRACKING EXAMPLES
There are four distinct variations that are easily implemented using the MIC22602. The two sequencing variations are
Delayed and Windowed. The two tracking variants are Normal and Ratio Metric. The following diagrams illustrate
methods for connecting two MIC22602’s to achieve these requirements.
Sequencing
FIGURE 5-3:
Circuit.
FIGURE 5-4:
Example.
FIGURE 5-5:
Example.
DS20006300A-page 16
Normal Tracking
Sequencing MIC22602
FIGURE 5-6:
Normal Tracking Circuit.
FIGURE 5-7:
Normal Tracking Example.
Window Sequencing
Delayed Sequencing
2020 Microchip Technology Inc.
MIC22602
Ratio Metric Tracking
DDR Memory VDD and VTT Tracking
FIGURE 5-8:
Circuit.
Ratio Metric Tracking
FIGURE 5-10:
Circuit.
DDR Memory Tracking
FIGURE 5-9:
Example.
Ratio Metric Tracking
FIGURE 5-11:
Example.
DDR Memory Tracking
An alternative method here shows an example of a VDDQ & VTT solution for a DDR memory power supply. Note that
POR is taken from VO1 as POR2 will not go high. This is because POR is set high when FB > 0.9 x VREF. In this
example, FB2 is regulated to ½VREF.
2020 Microchip Technology Inc.
DS20006300A-page 17
MIC22602
5.10
Current Limit
The MIC22602 is protected against overload in two
stages. The first is to limit the current in the P-channel
switch; the second is by overtemperature shutdown.
Current is limited by measuring the current through the
high-side MOSFET during its power stroke and
immediately switching off the driver when the preset
limit is exceeded.
The circuit in Figure 5-12 describes the operation of the
current-limit circuit. Because the actual RDS(ON) of the
P-Channel MOSFET varies part-to-part, over
temperature and with input voltage, simple IR voltage
detection is not employed. Instead, a smaller copy of
the Power MOSFET (Reference FET) is fed with a
constant current that is directly proportional to the
factory set current limit. This sets the current limit as a
current ratio and is not dependent upon the RDS(ON)
value. Current limit is set to 6A nominal. Variations in
the scale factor K between the Power PFET and the
reference PFET used to generate the limit threshold
account for a relatively small inaccuracy.
EQUATION 5-8:
T J = T A + P DISS R JA
Where:
PDISS = The power dissipated within the QFN
package and is typically 1.5W at 6A load. This has
been calculated for a 1 μH inductor and details can
be found in Table 5-2 for reference.
RθJA = A combination of junction to case thermal
resistance (RθJC) and Case-to-Ambient thermal
resistance (RθCA), since thermal resistance of the
solder connection from the ePad to the PCB is
negligible; RθCA is the thermal resistance of the
ground plane to ambient, so RθJA = RθJC + RθCA.
TA = The operating ambient temperature.
Example:
The Evaluation Board has two copper planes that
contribute to an RθJA of approximately 25°C/W. The
worst case RθJC of the QFN 4 mm x 4 mm is 14°C/W.
EQUATION 5-9:
R JA = R JC + R CA
R JA = 14C/W + 25C/W = 39C/W
To calculate the junction temperature for a 50°C
ambient:
EQUATION 5-10:
FIGURE 5-12:
5.11
Current Limit Detail.
T J = T A + P DISS R JA
Thermal Considerations
The MIC22602 is packaged in a 4 mm x 4 mm QFN, a
package that has excellent thermal performance
equaling that of the larger TSSOP packages. This
maximizes heat transfer from the junction to the
exposed pad (ePad) that connects to the ground plane.
The size of the ground plane attached to the exposed
pad determines the overall thermal resistance from the
junction to the ambient air surrounding the printed
circuit board. The junction temperature for a given
ambient temperature can be calculated using:
DS20006300A-page 18
T J = 50C + 1.5W 39C/W
T J = 108.5C
This is below the maximum of 125°C.
TABLE 5-2:
VOUT
at 6A
POWER DISSIPATION FOR 6A
OUTPUT
VIN
2.6V
3.3V
3.6V
4.5V
5V
5.5V
0.7V
1.41W
1.269W 1.209W 1.192W 1.198W 1.202W
1.2V
1.43W
1.276W 1.220W 1.206W 1.207W 1.214W
1.8V
1.48W
1.292W 1.230W 1.221W 1.218W 1.231W
2.5V
—
1.295W 1.228W 1.215W 1.224W 1.230W
3.3V
—
—
1.216W 1.208W 1.201W 1.224W
2020 Microchip Technology Inc.
MIC22602
5.12
Ripple Measurements
To properly measure ripple on either input or output of
a switching regulator, a proper ring in tip measurement
is required. Standard oscilloscope probes come with a
grounding clip, or a long wire with an alligator clip.
Unfortunately, for high frequency measurements, this
ground clip can pick up high frequency noise and
erroneously inject it into the measured output ripple.
The standard evaluation board accommodates a home
made version by providing probe points for both the
input and output supplies and their respective grounds.
This requires the removing of the oscilloscope probe
sheath and ground clip from a standard oscilloscope
probe and wrapping a non shielded bus wire around
the oscilloscope probe. If there does not happen to be
any non shielded bus wire immediately available, the
leads from axial resistors will work. By maintaining the
shortest possible ground lengths on the oscilloscope
probe, true ripple measurements can be obtained.
FIGURE 5-13:
Probe.
Standard Oscilloscope
2020 Microchip Technology Inc.
DS20006300A-page 19
MIC22602
6.0
PACKAGING INFORMATION
6.1
Package Marking Information
24-Lead QFN*
XXXXX
XXX
WNNN
Legend: XX...X
Y
YY
WW
NNN
e3
*
Example
22602
YML
7819
Product code or customer-specific information
Year code (last digit of calendar year)
Year code (last 2 digits of calendar year)
Week code (week of January 1 is week ‘01’)
Alphanumeric traceability code
Pb-free JEDEC® designator for Matte Tin (Sn)
This package is Pb-free. The Pb-free JEDEC designator ( e3 )
can be found on the outer packaging for this package.
●, ▲, ▼ Pin one index is identified by a dot, delta up, or delta down (triangle
mark).
Note:
In the event the full Microchip part number cannot be marked on one line, it will
be carried over to the next line, thus limiting the number of available
characters for customer-specific information. Package may or may not include
the corporate logo.
Underbar (_) and/or Overbar (‾) symbol may not be to scale.
DS20006300A-page 20
2020 Microchip Technology Inc.
MIC22602
24-Lead QFN 4 mm x 4 mm Package Outline and Recommended Land Pattern
Note:
For the most current package drawings, please see the Microchip Packaging Specification located at
http://www.microchip.com/packaging.
2020 Microchip Technology Inc.
DS20006300A-page 21
MIC22602
NOTES:
DS20006300A-page 22
2020 Microchip Technology Inc.
MIC22602
APPENDIX A:
REVISION HISTORY
Revision A (February 2020)
• Converted Micrel document MIC22602 to Microchip data sheet template DS20006300A.
• Minor grammatical text changes throughout.
• Evaluation Board Schematic, BOM, and PCB Layout sections from original data sheet moved to the
part’s Evaluation Board User’s Guide.
2020 Microchip Technology Inc.
DS20006300A-page 23
MIC22602
NOTES:
DS20006300A-page 24
2020 Microchip Technology Inc.
MIC22602
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, contact your local Microchip representative or sales office.
Examples:
Device
X
XX
-XX
Part No.
Junction
Temp. Range
Package
Media Type
Device:
MIC22602:
1 MHz, 6A Integrated Switch High
Efficiency Synchronous Buck Regulator
Junction
Temperature
Range:
Y
=
–40°C to +125°C, RoHS-Compliant
Package:
ML
=
24-Lead 4 mm x 4 mm QFN
Media Type:
TR
=
5,000/Reel
2020 Microchip Technology Inc.
a) MIC22602YML-TR:
Note 1:
MIC22602,
–40°C to +125°C Temperature
Range, 24-Lead QFN,
5,000/Reel
Tape and Reel identifier only appears in the
catalog part number description. This identifier is
used for ordering purposes and is not printed on
the device package. Check with your Microchip
Sales Office for package availability with the
Tape and Reel option.
DS20006300A-page 25
MIC22602
NOTES:
DS20006300A-page 26
2020 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.
Trademarks
The Microchip name and logo, the Microchip logo, Adaptec,
AnyRate, AVR, AVR logo, AVR Freaks, BesTime, BitCloud, chipKIT,
chipKIT logo, CryptoMemory, CryptoRF, dsPIC, FlashFlex,
flexPWR, HELDO, IGLOO, JukeBlox, KeeLoq, Kleer, LANCheck,
LinkMD, maXStylus, maXTouch, MediaLB, megaAVR, Microsemi,
Microsemi logo, MOST, MOST logo, MPLAB, OptoLyzer,
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Prochip Designer, QTouch, SAM-BA, SenGenuity, SpyNIC, SST,
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are registered trademarks of Microchip Technology Incorporated in
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APT, ClockWorks, The Embedded Control Solutions Company,
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TimePictra, TimeProvider, Vite, WinPath, and ZL are registered
trademarks of Microchip Technology Incorporated in the U.S.A.
Adjacent Key Suppression, AKS, Analog-for-the-Digital Age, Any
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SQTP is a service mark of Microchip Technology Incorporated in
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The Adaptec logo, Frequency on Demand, Silicon Storage
Technology, and Symmcom are registered trademarks of Microchip
Technology Inc. in other countries.
GestIC is a registered trademark of Microchip Technology Germany
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All other trademarks mentioned herein are property of their
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© 2020, Microchip Technology Incorporated, All Rights Reserved.
For information regarding Microchip’s Quality Management Systems,
please visit www.microchip.com/quality.
2020 Microchip Technology Inc.
ISBN: 978-1-5224-5579-0
DS20006300A-page 27
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05/14/19
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