2015 Microchip Technology Inc. DS20005549A-page 1
MIC2875
Features
• Up to 95% Efficiency
• Input Voltage Range: 2.5V to 5.5V
• Fully-Integrated, High-Efficiency, 2 MHz
Synchronous Boost Regulator
• Bi-Directional True Load Disconnect
• Integrated Anti-Ringing Switch
• Minimum Switching Frequency of 45 kHz
• <1 A Shutdown Current
• Bypass Mode for VIN VOUT
• Overcurrent Protection and Thermal Shutdown
• Fixed and Adjustable Output Versions
• 8-pin 2 mm × 2 mm TDFN Package
Applications
• Tablet and Smartphones
• USB OTG and HDMI Hosts
• Portable Power Reserve Supplies
• Low-Noise Audio Applications
• Portable Equipment
General Description
The MIC2875 is a compact and highly-efficient 2 MHz
synchronous boost regulator with a 4.8A switch. It
features a bi-directional load disconnect function which
prevents any leakage current between the input and
output when the device is disabled. The MIC2875
operates in bypass mode automatically when the input
voltage is greater than the target output voltage. At light
loads, the boost converter goes to the PFM mode to
improve the efficiency.
To minimize switching artifacts in the audio band, the
MIC2875 is designed to operate with a minimum
switching frequency of 45 kHz. The MIC2875 also
features an integrated anti-ringing switch to minimize
EMI.
The MIC2875 is available in a 8-pin 2 mm × 2 mm Thin
DFN (TDFN) package, with a junction temperature
range of –40°C to +125°C.
Package Type
MIC2875 (FIXED OUTPUT)
8-Pin 2x2 TDFN* (MT)
(Top View)
MIC2875 (ADJ. OUTPUT)
8-Pin 2x2 TDFN* (MT)
(Top View)
SW
PGND
IN
A
GND
OUT
/PG
EN
FB
▲
EP
1
2
3
45
6
7
8
SW
PGND
IN
A
GND
OUT
/PG
EN
OUTS
▲
EP
1
2
3
45
6
7
8
* Includes exposed thermal pad (EP), see Table 3-1.
4.8A ISW, Synchronous Boost Regulator
with Bi-Directional Load Disconnect
MIC2875
DS20005549A-page 2 2015 Microchip Technology Inc.
Typical Application Schematics
Functional Block Diagrams
AGND
SW
IN
EN
PGND
OUT
/PG
FB
V
IN
V
OUT
5.0V
L1 1μH
2.5V to 5.0V
C1
4.7μF
10V V
IN
R1
1MΩ R2
910kΩ
R3
200kΩ
C2*
22μF
10V
MIC2875 (Adjustable Output)MIC2875 (Fixed Output)
AGND
SW
V
IN
IN
EN
PGND
OUT
/PG
OUTS
V
OUT
5.0V
L1 1μH
2.5V to 5.0V
C1
4.7μF
10V V
IN
R1
1MΩ C2*
22μF
10V
* Two more 22F capacitors should be added in parallel with C2 for VIN > 5.0V.
50
60
70
80
90
100
0.001 0.010 0.100 1.000
EFFICIENCY (%)
LOAD CURRENT (A)
V
IN
= 3.6V
V
IN
= 3.0V
V
IN
= 2.5V
V
OUT
=5.0V
L = 1μH
C
OUT
= 22μF
Efficiency vs. Load Current
MIC2875 (Fixed Output) MIC2875 (Adj. Output)
EN IN SW
ANTI-
RINGING
REFERENCE
GENERATOR
2MHz
OSCILLATOR
OC
4.8A
PWM LOGIC
CONTROL
+
MINIMUM
SWITCHING
CURRENT
SENSE
+
SLOPE
COMPENSATION
VIN
OUT
BODY
DRIVER
HS
DRIVER
LS
DRIVER
/PG
PGND AGND
VREF SOFT-
START
PWM
OUTS
VIN
EN IN SW
ANTI-
RINGING
REFERENCE
GENERATOR
2MHz
OSCILLATOR
OC
4.8A
PWM LOGIC
CONTROL
+
MINIMUM
SWITCHING
CURRENT
SENSE
+
SLOPE
COMPENSATION
VIN
OUT
BODY
DRIVER
HS
DRIVER
LS
DRIVER
PGL
PGH
/PG
FB
PGND AGND
VREF SOFT-
START
PWM
2015 Microchip Technology Inc. DS20005549A-page 3
MIC2875
1.0 ELECTRICAL CHARACTERISTICS
Absolute Maximum Ratings †
IN, EN, OUT, FB, /PG to PGND ................................................................................................................... –0.3V to +6V
AGND to PGND......................................................................................................................................... –0.3V to +0.3V
Power Dissipation ....................................................................................................................Internally Limited (Note 1)
ESD Rating (Note 2) ................................................................................................................ ±1.5 kV HBM, ±200V MM
Operating Ratings ††
Supply Voltage (VIN).............................................................................................................................. +2.5V to +5.5V
Output Voltage (VOUT) ................................................................................................................................... Up to +5.5V
Enable Voltage (VEN) ....................................................................................................................................... 0V to +VIN
† Notice: Exceeding the absolute maximum ratings may damage the device.
†† Notice: The device is not guaranteed to function outside its operating ratings.
Note 1: The maximum allowable power dissipation of any TA (ambient temperature) is PD(max) = (TJ(max) – TA) / JA.
Exceeding the maximum allowable power dissipation will result in excessive die temperature, and the reg-
ulator will go into thermal shutdown
2: Devices are ESD sensitive. Handling precautions are recommended. Human body model, 1.5 k
in series with 100 pF.
MIC2875
DS20005549A-page 4 2015 Microchip Technology Inc.
TABLE 1-1: ELECTRICAL CHARACTERISTICS (Note 1)
Electrical Characteristics: VIN = 3.6V, VOUT = 5V, CIN = 4.7 F, COUT = 22 F, L = 1 H TA = 25°C, bold values are
valid for –40°C TJ +125°C Unless otherwise indicated.
Parameters Sym. Min. Typ. Max. Units Conditions
Power Supply
Supply Voltage Range VIN 2.5 —5.5 V—
UVLO Rising Threshold VUVLOR —2.32 2.49 V—
UVLO Hysteresis VUVLOH —200 —mV —
Quiescent Current IVIN —1—mA Operating at minimum
switching frequency
VIN Shutdown Current IVINSD —13AV
EN = 0V, VIN = 5.5V, VOUT =
0V
VOUT Shutdown Current IVOUTSD —25AV
EN = 0V, VIN = 0.3V, VOUT =
5.5V
Output Voltage VOUT VIN — 5.5 V —
Feedback Voltage VFB 0.8865 0.9 0.9135 V Adjustable version, IOUT = 0A
Voltage Accuracy —1.5 —+1.5 % Fixed version, IOUT = 0A
Line Regulation ——
0.3 —%/V 2.5V < VIN < 4.5V, IOUT =
500 mA
Load Regulation ——
0.2 —%/A IOUT = 200 mA to 1200 mA
Maximum Duty Cycle DMAX —92 —%—
Minimum Duty Cycle DMIN —6.5 —%—
Low-side Switch Current
Limit ILS
3.8 4.8 5.8 A VIN = 2.5V
Switch On-Resistance PMOS —79 —mVIN = 3.0V, ISW = 200 mA,
VOUT = 5.0V
NMOS —82 —mVIN = 3.0V, ISW = 200 mA,
VOUT = 5.0V
Switch Leakage Current
(Note 2)
ISW —0.2 5AV
EN = 0V, VIN = 5.5V
Minimum Switching
Frequency
FSWMIN —45 —kHz IOUT = 0 mA
Oscillator Frequency FOSC 1.6 22.4 MHz —
Overtemperature
Shutdown Threshold TSD
—155 —
°C
—
Overtemperature
Shutdown Hysteresis —15 ——
Soft-Start
Soft-Start Time TSS —1.1 —ms VOUT = 5.0V
Note 1: Specification for packaged product only.
2: Guaranteed by design and characterization.
2015 Microchip Technology Inc. DS20005549A-page 5
MIC2875
EN, /PG Control Pins
EN Threshold Voltage VEN
1.5 ——
V
Boost converter and chip logic
ON
——0.4 Boost converter and chip logic
OFF
EN Pin Current ——1.5 3AVIN = VEN = 3.6V
Power-Good Threshold
(Rising)
V/PG-THR —0.90 ×
VOUT
—V—
Power-Good Threshold
(Falling) V/PG-THF —0.83 ×
VOUT
—V—
TABLE 1-1: ELECTRICAL CHARACTERISTICS (CONTINUED)(Note 1)
Electrical Characteristics: VIN = 3.6V, VOUT = 5V, CIN = 4.7 F, COUT = 22 F, L = 1 H TA = 25°C, bold values are
valid for –40°C TJ +125°C Unless otherwise indicated.
Parameters Sym. Min. Typ. Max. Units Conditions
Note 1: Specification for packaged product only.
2: Guaranteed by design and characterization.
MIC2875
DS20005549A-page 6 2015 Microchip Technology Inc.
TEMPERATURE SPECIFICATIONS (Note 1)
Parameters Sym. Min. Typ. Max. Units Conditions
Temperature Ranges
Lead Temperature — — 260 — °C Soldering 10s
Storage Temperature Range TS–65 — +150 °C —
Junction Operating Temperature TJ–40 — +125 °C —
Package Thermal Resistances
Thermal Resistance, TDFN-22-8Ld JA — 90 — °C/W —
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.
2015 Microchip Technology Inc. DS20005549A-page 7
MIC2875
2.0 TYPICAL PERFORMANCE CURVES
FIGURE 2-1: Efficiency vs. Load Current.
FIGURE 2-2: Output Voltage vs. Load
Current.
FIGURE 2-3: Output Voltage vs. Input
Voltage.
FIGURE 2-4: Oscillator Frequency vs.
Temperature.
FIGURE 2-5: Output Shutdown Current
vs. Temperature.
FIGURE 2-6: Feedback Voltage vs.
Temperature.
50
60
70
80
90
100
0.001 0.010 0.100 1.000
EFFICIENCY (%)
LOAD CURRENT (A)
V
IN
= 3.6V
V
IN
= 3.0V
V
IN
= 2.5V
V
OUT
=5.0V
L = 1μH
C
OUT
= 22μF
4.90
4.95
5.00
5.05
5.10
0.0 0.5 1.0 1.5 2.0
OUTPUT VOLTAGE (V)
LOAD CURRENT
(
A
)
V
IN
=3.5V
V
OUT
=5.0V
L = 1μH
C
OUT
= 22μF
T
A
= 125℃
T
A
= -40℃
ADJUSTABLE
R2 = 910kΩ
R3 = 200kΩ
T
A
= 25℃
4.80
4.90
5.00
5.10
5.20
2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT VOLTAGE (V)
INPUT VOLTAGE(V)
V
OUT
=5.0V
L = 1μH
C
OUT
= 22μF
I
OUT
= 500mA
ADJUSTABLE
R2 = 910kΩ
R3 = 200kΩ
T
A
= 125℃
T
A
= 25℃
T
A
= -40℃
1.96
1.98
2.00
2.02
2.04
-50-250 255075100125150
OSCILLATOR FREQUENCY (MHz)
TEMPERATURE (
℃
)
V
IN
=3.6V
V
OUT
=5.0V
L = 1μH
C
OUT
= 22μF
I
OUT
= 0A
1.00
1.50
2.00
2.50
3.00
3.50
4.00
-50 -25 0 25 50 75 100 125 150
SHUTDOWN CURRENT (µA)
TEMPERATURE (
℃
)
V
EN
=0V
V
IN
= 0.3V
V
OUT
= 5.5V
ADJUSTABLE
R2 = 910kΩ
R3 = 200kΩ
0.896
0.898
0.900
0.902
0.904
-50 -25 0 25 50 75 100 125 150
FEEDBACK VOLTAGE (V)
TEMPERATURE
(℃)
ADJUSTABLE
VOUT = 5.0V
R2 = 910kΩ
R3 = 200kΩ
MIC2875
DS20005549A-page 8 2015 Microchip Technology Inc.
FIGURE 2-7: UVLO Threshold vs.
Temperature.
FIGURE 2-8: Enable Threshold vs.
Temperature.
FIGURE 2-9: Power Good Threshold vs.
Temperature.
FIGURE 2-10: Load Transient (0A to 1.2A).
.
FIGURE 2-11: Load Transient (1.2A to 0A).
.
FIGURE 2-12: Line Transient (2.5V to
3.5V).
2.00
2.10
2.20
2.30
2.40
-50-25 0 255075100125150
INPUT VOLTAGE (V)
TEMPERATURE (
℃
)
RISING
FALLING
0.60
0.80
1.00
1.20
-50 -25 0 25 50 75 100 125 150
ENABLE THRESHOLD VOLTAGE (V)
TEMPERATURE (
℃
)
RISING
FALLING
3.80
4.00
4.20
4.40
4.60
4.80
-50 -25 0 25 50 75 100 125 150
POWER GOOD THRESHOLD VOLTAGE (V)
TEMPERATURE (
℃
)
RISING
FALLING
ADJUSTABLE
R2 = 910kΩ
R3 = 200kΩ
V
OUT
=5.0V
V
IN
= 3.5V, V
OUT
= 5.0V
L = 1μH, I
OUT
= 0A TO 1.2A
Time (100μs/div)
I
OUT
(1A/div)
V
SW
(5V/div)
V
/PG
(2V/div)
V
OUT
(1V/div)
(AC-COUPLED)
Time (100μs/div)
I
OUT
(1A/div)
V
SW
(5V/div)
V
/PG
(2V/div)
V
OUT
(1V/div)
(AC-COUPLED) V
IN
= 3.5V, V
OUT
= 5.0V
L = 1μH, I
OUT
= 1.2A TO 0A
Time (100μs/div)
I
L
(2A/div)
V
IN
(2V/div)
V
OUT
(5V/div)
V
OUT
(500mV/div)
(AC-COUPLED)
V
IN
= 2.5V TO 3.5V
V
OUT
= 5.0V
L = 1μH
I
OUT
= 1A
2015 Microchip Technology Inc. DS20005549A-page 9
MIC2875
.
FIGURE 2-13: Line Transient (3.5V to
2.5V).
.
FIGURE 2-14: Line Transient (2.5V to
5.5V).
FIGURE 2-15: Line Transient (5.5V to
2.5V).
FIGURE 2-16: Output Ripple (Pulse Skipping
Mode).
FIGURE 2-17: Output Ripple (PWM Mode).
FIGURE 2-18: Soft–Start (Boost Mode).
Time (100μs/div)
I
L
(2A/div)
V
IN
(2V/div)
V
OUT
(5V/div)
V
OUT
(500mV/div)
(AC-COUPLED)
V
IN
= 3.5V TO 2.5V, V
OUT
= 5.0V
L = 1μH, I
OUT
= 1A
Time (100μs/div)
I
L
(5A/div)
V
IN
(2V/div)
V
OUT
(5V/div)
V
OUT
(2V/div)
(AC-COUPLED)
V
IN
= 2.5V TO 5.5V
V
OUT
= 5.0V
L = 1μH
I
OUT
= 1A
Time (100μs/div)
I
L
(5A/div)
V
IN
(2V/div)
V
OUT
(5V/div)
V
OUT
(2V/div)
(AC-COUPLED)
V
IN
= 5.5V TO 2.5V
V
OUT
= 5.0V, L = 1μH
I
OUT
= 1A
PULSE SKIPPING MODE
V
IN
= 3.5V, V
OUT
= 5.0V, I
OUT
= 50mA
Time (4μs/div)
I
L
(200mA/div)
V
SW
(2V/div)
V
OUT
(50mV/div)
(AC-COUPLED)
PWM MODE
V
IN
= 3.5V, V
OUT
= 5.0V, I
OUT
= 1.2A
Time (200ns/div)
I
L
(1A/div)
V
SW
(5V/div)
V
OUT
(50mV/div)
(AC-COUPLED)
BOOST MODE
V
IN
= 3.5V
V
OUT
= 5.0V
I
OUT
= 500mA
Time (400μs/div)
I
L
(1A/div)
V
EN
(2V/div)
V
/PG
(2V/div)
V
OUT
(5V/div)
MIC2875
DS20005549A-page 10 2015 Microchip Technology Inc.
FIGURE 2-19: Soft–Start Bypass Mode.
FIGURE 2-20: Minimum Switching.
FIGURE 2-21: Minimum Switching
(Zoom–In).
FIGURE 2-22: Bypass mode.
FIGURE 2-23: Bypass Mode.
BYPASS MODE
V
IN
= 5.5V
V
OUT
= 5.0V
I
OUT
= 500mA
Time (400μs/div)
I
L
(1A/div)
V
EN
(2V/div)
V
/PG
(5V/div)
V
OUT
(5V/div)
V
IN
= 3.5V, F
SWMIN
= 45kHz, I
OUT
= 0A
Time (20μs/div)
I
L
(200mA/div)
V
SW
(2V/div)
Time (400ns/div)
I
L
(200mA/div)
V
SW
(2V/div) V
IN
= 3.5V
F
SWMIN
= 45kHz
I
OUT
= 0A
Time (1s/div)
V
IN
(1V/div)
V
OUT
(1V/div)
BYPASS MODE – V
IN
> 5.0V
V
OUT
= V
IN
I
OUT
= 0A
V
OUT
= 5.0V V
OUT
= 5.0V
Time (1s/div)
V
IN
(1V/div)
V
OUT
(1V/div)
BYPASS MODE – V
IN
> 5.0V
V
OUT
= V
IN
I
OUT
= 500mA
V
OUT
= 5.0V V
OUT
= 5.0V
2015 Microchip Technology Inc. DS20005549A-page 11
MIC2875
3.0 PIN DESCRIPTIONS
The descriptions of the pins are listed in Table 3-1.
TABLE 3-1: PIN FUNCTION TABLE
Pin Number
Fixed Output Pin Number
Adj. Output Pin Name Description
1 1 SW Boost Converter Switch Node: Connect the inductor between
IN and SW pins.
2 2 PGND Power Ground: The power ground for the synchronous boost
DC/DC converter power stage.
3 3 IN Supply Input: Connect at least 1 F ceramic capacitor between
IN and AGND pins.
4 4 AGND Analog Ground: The analog ground for the regulator control
loop.
5 — OUTS Output Voltage Sense Pin: For output voltage regulation in fixed
voltage version. Connect to the boost converter output.
— 5 FB Feedback Pin: For output voltage regulation in adjustable
version. Connect to the feedback resistor divider.
6 6 EN Boost Converter Enable: When this pin is driven low, the IC
enters shutdown mode. The EN pin has an internal 2.5 M
pull-down resistor. The output is disabled when this pin is left
floating.
7 7 /PG Open Drain Power Good Output (Active Low): The /PG pin is
high impedance when the output voltage is below the power
good threshold and becomes low once the output is above the
power good threshold. The /PG pin has a typical RDS(ON) = 90
and requires a pull up resistor of 1 M. Connect /PG pin to
AGND when the /PG signal is not used.
8 8 OUT Boost Converter Output.
EP EP ePad Exposed Heat Sink Pad. Connect to AGND for best thermal
performance.
MIC2875
DS20005549A-page 12 2015 Microchip Technology Inc.
4.0 FUNCTIONAL DESCRIPTION
4.1 Input (IN)
The input supply provides power to the internal
MOSFETs gate drivers and control circuitry for the
boost regulator. The operating input voltage range is
from 2.5V to 5.5V. A 1 F low-ESR ceramic input
capacitor should be connected from IN to AGND as
close to MIC2875 as possible to ensure a clean supply
voltage for the device. A minimum voltage rating of 10V
is recommended for the input capacitor.
4.2 Switch Node (SW)
The MIC2875 has internal low-side and synchronous
MOSFET switches. The switch node (SW) between the
internal MOSFET switches connects directly to one
end of the inductor and provides the current path during
switching cycles. The other end of the inductor is
connected to the input supply voltage. Due to the
high-speed switching on this pin, the switch node
should be routed away from sensitive nodes wherever
possible.
4.3 Ground Path (AGND)
The ground path (AGND) is for the internal biasing and
control circuitry. AGND should be connected to the
PCB pad for the package exposed pad. The current
loop of the analog ground should be separated from
that of the power ground (PGND). AGND should be
connected to PGND and EP at a single point.
4.4 Power Ground (PGND)
The power ground (PGND) is the ground path for the
high current in the boost switches. The current loop for
the power ground should be as short as possible and
separate from the AGND loop as applicable.
4.5 Boost Converter Output (OUT)
A low-ESR ceramic capacitor of 22 F (for operation
with VIN 5.0V), or 66 F (for operation with VIN >
5.0V) should be connected from VOUT to PGND as
close as possible to the MIC2875. A minimum voltage
rating of 10V is recommended for the output capacitor.
4.6 Enable (EN)
Enable pin of the MIC2875. A logic high on this pin
enables the MIC2875. When this pin is driven low, the
MIC2875 enters the shutdown mode. When the EN pin
is left floating, it is pulled-down internally by a built-in
2.5 M resistor.
4.7 Feedback/Output Voltage Sense
(FB/OUTS)
Feedback or output voltage sense pin for the boost
converter. For the fixed voltage version, this pin should
be connected to the OUT pin. For the adjustable
version, connect a resistor divider to set the output
voltage (see “Section 5.7 “Output Voltage
Programming”” for more information).
4.8 Power Good Output (/PG)
The open-drain active-low power-good output (/PG) is
low when the output voltage is above the power-good
threshold. A pull-up resistor of 1 M is recommended.
4.9 Exposed Heat Sink Pad (EP)
The exposed heat sink pad, or ePad (EP), should be
connected to AGND for best thermal performance.
2015 Microchip Technology Inc. DS20005549A-page 13
MIC2875
5.0 APPLICATION INFORMATION
5.1 General Description
The MIC2875 is a 2 MHz, current-mode, PWM,
synchronous boost converter with an operating input
voltage range of 2.5V to 5.5V. At light load, the
converter enters pulse-skipping mode to maintain high
efficiency over a wide range of load current. The
maximum peak current in the boost switch is limited to
4.8A (typical).
5.2 Bi-Directional Output Disconnect
The power stage of the MIC2875 consists of a NMOS
transistor as the main switch and a PMOS transistor as
the synchronous rectifier. A control circuit turns off the
back gate diode of the PMOS to isolate the output from
the input supply when the chip is disabled (VEN = 0V).
An “always on” maximum supply selector switches the
cathode of the back-gate diode to either the IN or the
OUT (whichever of the two has the higher voltage). As
a result, the output of the MIC2875 is bi-directionally
isolated from the input as long as the device is
disabled. The maximum supply selector and hence the
output disconnect function requires only 0.3V at the IN
pin to operate.
5.3 Minimum Switching Frequency
When the MIC2875 enters the pulse-skipping mode for
more than 20 s, an internal control circuitry forces the
PMOS to turn on briefly to discharge VOUT to VIN
through the inductor. When the inductor current
reaches a predetermined threshold, the PMOS is
turned off and the NMOS is turned on so that the
inductor current can decrease gradually. Once the
inductor current reaches zero, the NMOS is eventually
turned off. The above cycle repeats if there is no
switching activity for another 20 s, effectively
maintaining a minimum switching frequency of 45 kHz.
The frequency control circuit is disabled when VOUT is
less than or within 200 mV of VIN. This minimum
switching frequency feature is advantageous for
applications that are sensitive to low-frequency EMI,
such as audio systems.
5.4 Integrated Anti-Ringing Switch
The MIC2875 includes an anti-ringing switch that
eliminates the ringing on the SW node of a
conventional boost converter operating in the
discontinuous conduction mode (DCM). At the end of a
switching cycle during DCM operation, both the NMOS
and PMOS are turned off. The anti-ringing switch in the
MIC2875 clamps the SW pin voltage to IN to dissipate
the remaining energy stored in the inductor and the
parasitic elements of the power switches.
5.5 Automatic Bypass Mode (when
VIN > VOUT)
The MIC2875 automatically operates in bypass mode
when the input voltage is higher than the target output
voltage. In bypass mode, the NMOS is turned off while
the PMOS is fully turned-on to provide a very low
impedance path from IN to OUT.
5.6 Soft-Start
The MIC2875 integrates an internal soft-start circuit to
limit the inrush current during start-up. When the device
is enabled, the PMOS is turned-on slowly to charge the
output capacitor to a voltage close to the input voltage.
Then, the device begins boost switching cycles to
gradually charge up the output voltage to the target
VOUT
.
5.7 Output Voltage Programming
The MIC2875 has an adjustable version that allows the
output voltage to be set by an external resistor divider
R2 and R3. The typical feedback voltage is 900 mV, the
recommended maximum and minimum output voltage
is 5.5V and 3.2V, respectively. The current through the
resistor divider should be significantly larger than the
current into the FB pin (typically 0.01 A). It is
recommended that 0.1% tolerance feedback resistors
must be used and the total resistance of R2 + R3
should be around 1 M. The appropriate R2 and R3
values for the desired output voltage are calculated as
in Equation 5-1:
EQUATION 5-1:
5.8 Current Limit Protection
The MIC2875 has a current limit feature to protect the
part against heavy loading condition. When the current
limit comparator determines that the NMOS switch has
a peak current higher than 4.8A, the NMOS is turned off
and the PMOS is turned on until the next switching
cycle. The overcurrent protection is reset cycle by cycle
R2R3VOUT
0.9V
---------------1–
=
MIC2875
DS20005549A-page 14 2015 Microchip Technology Inc.
6.0 COMPONENT SELECTION
6.1 Inductor
Inductor selection is a trade-off between efficiency,
stability, cost, size, and rated current. Because the
boost converter is compensated internally, the
recommended inductance is limited from 1 H to
2.2 H to ensure system stability and presents a good
balance between these considerations.
A large inductance value reduces the peak-to-peak
inductor ripple current hence the output ripple voltage.
This also reduces both the DC loss and the transition
loss at the same inductor’s DC resistance (DCR).
However, the DCR of an inductor usually increases
with the inductance in the same package size. This is
due to the longer windings required for an increase in
inductance. Since the majority of the input current
passes through the inductor, the higher the DCR the
lower the efficiency is, and more significantly at higher
load currents. On the other hand, inductor with smaller
DCR but the same inductance usually has a larger size.
The saturation current rating of the selected inductor
must be higher than the maximum peak inductor
current to be encountered and should be at least 20%
to 30% higher than the average inductor current at
maximum output current.
6.2 Input Capacitor to the Device
Supply
A ceramic capacitor of 1 F or larger with low ESR is
recommended to reduce the input voltage ripple to
ensure a clean supply voltage for the device. The input
capacitor should be placed as close as possible to the
MIC2875 IN pin and AGND pin with short traces to
ensure good noise performance. X5R or X7R type
ceramic capacitors are recommended for better
tolerance over temperature. The Y5V and Z5U type
temperature rating ceramic capacitors are not
recommended due to their large reduction in
capacitance over temperature and increased
resistance at high frequencies. The use of these
reduces the ability to filter out high-frequency noise.
The rated voltage of the input capacitor should be at
least 20% higher than the maximum operating input
voltage over the operating temperature range.
6.3 Input Capacitor to the Power Path
A ceramic capacitor of a 4.7 F of larger with low ESR
is recommended to reduce the input voltage fluctuation
at the voltage supply of the high current power path. An
input capacitor should be placed close to the VIN supply
to the power inductor and PGND for good device
performance at heavy load condition. X5R or X7R type
ceramic capacitors are recommended for better
tolerance overtemperature.
The Y5V and Z5U type temperature rating ceramic
capacitors are not recommended due to their large
reduction in capacitance over temperature and
increased resistance at high frequencies. These
reduce their ability to filter out high-frequency noise.
The rated voltage of the input capacitor should be at
least 20% higher than the maximum operating input
voltage over the operating temperature range.
6.4 Output Capacitor
Output capacitor selection is also a trade-off between
performance, size, and cost. Increasing output
capacitor will lead to an improved transient response,
however, the size and cost also increase. For operation
with VIN 5.0V, a minimum of 22 F output capacitor
with ESR less than 10 m is required. For operation
with VIN > 5.0V, a minimum of 66 F output capacitor
with ESR less than 10 m is required. X5R or X7R type
ceramic capacitors are recommended for better
tolerance over temperature. Additional capacitors can
be added to improve the transient response, and to
reduce the ripple of the output when the MIC2875
operates in and out of bypass mode.
The Y5V and Z5U type ceramic capacitors are not
recommended due to their wide variation in
capacitance over temperature and increased
resistance at high frequencies. The rated voltage of the
output capacitor should be at least 20% higher than the
maximum operating output voltage over the operating
temperature range. 0805 size ceramic capacitor is
recommended for smaller ESL at output capacitor
which contributes smaller voltage spike at the output
voltage of high-frequency switching boost converter.
2015 Microchip Technology Inc. DS20005549A-page 15
MIC2875
7.0 POWER DISSIPATION
As with all power devices, the ultimate current rating of
the output is limited by the thermal properties of the
device package and the PCB on which the device is
mounted. There is a simple, Ohm’s law-type
relationship between thermal resistance, power
dissipation, and temperature which are analogous to
an electrical circuit (see Figure 7-1):
FIGURE 7-1: Series Electrical Resistance
Circuit.
From this simple circuit we can calculate VX if we know
ISOURCE, VZ, and the resistor values, RXY and RYZ
using Equation 7-1:
EQUATION 7-1:
Thermal circuits can be considered using this same
rule and can be drawn similarly by replacing current
sources with power dissipation (in watts), resistance
with thermal resistance (in °C/W) and voltage sources
with temperature (in °C).
FIGURE 7-2: Series Thermal Resistance
Circuit.
Now replacing the variables in the equation for VX, we
can find the junction temperature (TJ) from the power
dissipation, ambient temperature and the known
thermal resistance of the PCB (CA) and the package
(JC).
EQUATION 7-2:
As can be seen in the diagram, total thermal resistance
JA = JC + CA. This can also be written as in
Equation 7-3:
EQUATION 7-3:
Given that all of the power losses (minus the inductor
losses) are effectively in the converter are dissipated
within the MIC2875 package, PDISS can be calculated
thusly:
EQUATION 7-4: LINEAR MODE
EQUATION 7-5: BOOST MODE
EQUATION 7-6: DUTY CYCLE (BOOST)
In the equations above, is the efficiency taken from
the efficiency curves and DCR represents the inductor
DCR. JC and JA are found in the temperature
specifications section of the data sheet.
Where the real board area differs from 1” square, CA
(the PCB thermal resistance), values for various PCB
copper areas can be taken from Figure 7-3.
VXISOURCE RXY RYZ
+VZ
+=
TJPDISS JC CA
+TA
+=
TJPDISS JA
TA
+=
PDISS POUT 1
--- 1–
IOUT2
–DCR=
PDISS POUT 1
--- 1–
IOUT
1D–
-------------
2
–DCR=
DVOUT VIN
–
VOUT
-------------------------------+
MIC2875
DS20005549A-page 16 2015 Microchip Technology Inc.
FIGURE 7-3: Determining PCB Area for a
Given PCB Thermal Resistance.
Figure 7-3 shows the total area of a round or square
pad, centered on the device. The solid trace represents
the area of a square, single-sided, horizontal, solder
masked, copper PC board trace heat sink, measured in
square millimeters. No airflow is assumed. The dashed
line shows the PC board’s trace heat sink covered in
black oil-based paint and with 1.3 m/sec (250 feet per
minute) airflow. This approaches a “best case” pad
heat sink. Conservative design dictates using the solid
trace data, which indicates that a maximum pad size of
5000 mm2 is needed. This is a pad 71 mm × 71 mm
(2.8 inches per side).
2015 Microchip Technology Inc. DS20005549A-page 17
MIC2875
8.0 PCB LAYOUT GUIDELINES
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 guidelines
should be followed to ensure proper operation of the
device. Please refer to the MIC2875 evaluation board
document for the recommended components
placement and layouts.
8.1 Integrated Circuit (IC)
• Place the IC close to the point-of-load.
• Use fat traces to route the input and output power
lines.
• Analog grounds and power ground should be kept
separate and connected at a single location at the
PCB pad for exposed pad of the IC.
• Place as much as thermal vias on the PCB pad
for exposed pad and connected it to the ground
plane to ensure a good PCB thermal resistance
can be achieved.
8.2 IN Decoupling Capacitor
• The IN decoupling capacitor must be placed close
to the IN pin of the IC and preferably connected
directly to the pin and not through any via. The
capacitor must be located right at the IC.
• The IN decoupling capacitor should be connected
as close as possible to AGND.
• The IN terminal is noise sensitive and the
placement of capacitor is very critical.
8.3 VIN Power Path Bulk Capacitor
• The VIN power path bulk capacitor should be
placed and connected close to the VIN supply to
the power inductor and the PGND of the IC.
• Use either X5R or X7R temperature rating
ceramic capacitors. Do not use Y5V or Z5U type
ceramic capacitors.
8.4 Inductor
• Keep both the inductor connections to the switch
node (SW) and input power line short and wide
enough to handle the switching current. Keep the
areas of the switching current loops small to
minimize the EMI problem.
• Do not route any digital lines underneath or close
to the inductor.
• Keep the switch node (SW) away from the noise
sensitive pins.
• To minimize noise, place a ground plane
underneath the inductor.
8.5 Output Capacitor
• Use wide and short traces to connect the output
capacitor as close as possible to the OUT and
PGND pins without going through via holes to
minimize the switching current loop during the
main switch off cycle and the switching noise.
• Use either X5R or X7R temperature rating
ceramic capacitors. Do not use Y5V or Z5U type
ceramic capacitors.
MIC2875
DS20005549A-page 18 2015 Microchip Technology Inc.
9.0 PACKAGING INFORMATION
8-Lead TDFN 2 mm x 2 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
2015 Microchip Technology Inc. DS20005549A-page 19
MIC2875
APPENDIX A: REVISION HISTORY
Revision A (May 2016)
• Converted Micrel document DSC2875 to Micro-
chip data sheet template DS20005549A.
• •Minor text changes throughout.
MIC2875
DS20005549A-page 20 2015 Microchip Technology Inc.
NOTES:
2016 Microchip Technology Inc. DS20005549A-page 21
MIC2875
PRODUCT IDENTIFICATION SYSTEM
To order or obtain information, e.g., on pricing or delivery, contact your local Microchip representative or sales office.
Examples:
a) MIC2875-4.75YMT: 4.8A ISW, Synchronous
Boost Regulator with Bi-
Directional Load Discon-
nect, 4.75V Output Voltage,
–40°C to +125°C Temp.
Range, 8-Pin TDFN
b) MIC2875-5.0YMT: 4.8A ISW, Synchronous
Boost Regulator with Bi-
Directional Load Discon-
nect, 5.00V Output Voltage,
–40°C to +125°C Temp.
Range, 8-Pin TDFN
c) MIC2875-5.25YMT: 4.8A ISW, Synchronous
Boost Regulator with Bi-
Directional Load Discon-
nect, 5.25V Output Voltage,
–40°C to +125°C Temp.
Range, 8-Pin TDFN
d) MIC2875-5.5YMT: 4.8A ISW, Synchronous
Boost Regulator with Bi-
Directional Load Discon-
nect, 5.50V Output Voltage,
–40°C to +125°C Temp.
Range, 8-Pin TDFN
e) MIC2875-AYMT: 4.8A ISW, Synchronous
Boost Regulator with Bi-
Directional Load Discon-
nect, Adjustable Output
Voltage, –40°C to +125°C
Temp. Range, 8-Pin TDFN
PART NO. XX
Package
Device
Device: MIC2875: 4.8A ISW, Synchronous Boost Regulator
with Bi-Directional Load Disconnect
Output Voltage: 4.75 = 4.75V
5.0 = 5.00V
5.25 = 5.25V
5.5 = 5.50V
A = Adjustable
Temperature: Y = –40°C to +125°C
Package: MT = 8-Pin 2 mm x 2 mm TDFN (Note 1)
XX
Output
–
Voltage
X
Temperature
Note 1: Thin DFN is an RoHS-compliant package. Lead finish is Pb-free
and Matte Tin. Mold compound is Halogen free.
= TDFN Pin 1 identifier
MIC2875
DS20005549A-page 22 2016 Microchip Technology Inc.
NOTES:
2016 Microchip Technology Inc. DS20005549A-page 23
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, AnyRate,
dsPIC, FlashFlex, flexPWR, Heldo, JukeBlox, KeeLoq,
KeeLoq logo, Kleer, LANCheck, LINK MD, MediaLB, MOST,
MOST logo, MPLAB, OptoLyzer, PIC, PICSTART, PIC32 logo,
RightTouch, SpyNIC, SST, SST Logo, SuperFlash and UNI/O
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.
Analog-for-the-Digital Age, Any Capacitor, AnyIn, AnyOut,
BodyCom, chipKIT, chipKIT logo, CodeGuard, dsPICDEM,
dsPICDEM.net, Dynamic Average Matching, DAM, ECAN,
EtherGREEN, In-Circuit Serial Programming, ICSP, Inter-Chip
Connectivity, JitterBlocker, KleerNet, KleerNet logo, MiWi,
motorBench, MPASM, MPF, MPLAB Certified logo, MPLIB,
MPLINK, MultiTRAK, NetDetach, Omniscient Code
Generation, PICDEM, PICDEM.net, PICkit, PICtail,
PureSilicon, RightTouch logo, REAL ICE, Ripple Blocker,
Serial Quad I/O, 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 trademarks 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.
© 2016, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
ISBN: 978-1-5224-0572-6
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.
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.
DS20005549A-page 24 2015 Microchip Technology Inc.
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