MP2276
The Future of Analog IC Technology
8A, 2.7-16V Input, High-Efficiency Synchronous
Step-down Converter with Programmable Current
Limit and Soft Start Time Selectable Frequency
and Mode of Operation
DESCRIPTION
FEATURES
The MP2276 is a fully integrated, highfrequency, synchronous, rectified, step-down,
switch-mode converter. It offers a very compact
solution that achieves up to 8A of continuous
output current with excellent load and line
regulation over a wide input supply range. The
MP2276 operates at high efficiency over a wide
output current load range.
The MP2276 uses constant-on-time (COT)
control for fast transient response and eased
loop stabilization.
Output voltage start-up is controlled by an
internal 1.7ms timer, which can be increased by
adding a capacitor on SS/TRK. An open-drain
power good (PG) signal indicates when the
output is within its nominal voltage range.
Full protection features include over-current
protection (OCP), over-voltage protection
(OVP), under-voltage protection (UVP), and
over-temperature protection (OTP).
The MP2276 requires a minimal number of
readily
available,
standard,
external
components and is available in a QFN-14
(2mmx3mm) package.
Wide 2.7V to 16V Input Voltage Range
8A Continuous Output Current
24mΩ/10mΩ Low RDS(ON) Integrated Power
MOSFETs
Adaptive Constant-On-Time (COT) for
Ultrafast Transient Response
Stable with Zero ESR Output Capacitor
Programmable Current Limit
Selectable Forced CCM or Pulse-Skip
Operation at Light Load
Excellent Load Regulation
Programmable Soft-Start Time from 1.7ms
Pre-Bias Start-Up
Selectable 600kHz, 1100kHz, or 2000kHz
Switching Frequency
Hiccup Over-Current Protection (OCP)
Auto-Retry Over-Voltage Protection (OVP)
and Thermal Shutdown
Output Adjustable from 0.8V
Available in a QFN-14 (2mmx3mm)
Package
APPLICATIONS
Digital Set-Top Boxes
Flat-Panel TV and Monitors
Distributed Power Systems
All MPS parts are lead-free, halogen-free, and adhere to the RoHS
directive. For MPS green status, please visit the MPS website under
Quality Assurance. “MPS” and “The Future of Analog IC Technology” are
registered trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
Efficiency vs. Output Current
VOUT = 1V, L = 1µH (DCR = 4.6mΩ)
100
Efficiency(%)
90
80
70
60
Vin=5V
Vin=12V
Vin=16V
50
40
0.01
MP2276 Rev.1.1
5/30/2018
0.10
1.00
Output Current(A)
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10.00
1
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
ORDERING INFORMATION
Part Number*
MP2276GD
Package
QFN-14 (2mmx3mm)
Top Marking
See Below
* For Tape & Reel, add suffix –Z (e.g. MP2276GD–Z)
TOP MARKING
AUM: Product code of MP2276GD
Y: Year code
WW: Week code
LLL: Lot number
PACKAGE REFERENCE
TOP VIEW
QFN-14 (2mmx3mm)
MP2276 Rev.1.1
5/30/2018
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2
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
ABSOLUTE MAXIMUM RATINGS (1)
Supply voltage (VIN) .................................... 18V
VSW (DC) ..............................-0.3V to VIN + 0.3V
VSW (25ns).......................................... -5V to 25V
VBST ...................................................... VSW + 4V
VCC .............................................................. 4V
EN current (IEN) ....................................... 300μA
All other pins ...................... -0.3V to VCC + 0.3V
(2)
Continuous power dissipation (TA = +25°C)
................................................................... 2.7W
Junction temperature ................................150°C
Lead temperature .....................................260°C
Storage temperature ................ -65°C to +150°C
Recommended Operating Conditions
(3)
Thermal Resistance
QFN-14 (2mmx3mm)
θJA
θJC
EV2276-D-00A ..................... 40 ....... 10 .... °C/W
JESD51-7 ............................. 46 ........ 9 ..... °C/W
NOTES:
1) Exceeding these ratings may damage the device.
2) The maximum allowable power dissipation is a function of the
maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature
TA. The maximum allowable continuous power dissipation at
any ambient temperature is calculated by PD (MAX) = (TJ
(MAX)-TA)/θJA. Exceeding the maximum allowable power
dissipation produces an excessive die temperature.
3) The device is not guaranteed to function outside of its
operating conditions.
4) For VIN≤3.3V application, please connect VIN to VCC
directly. And 2.7V is only a typical value for minimum supply
voltage at VIN falling.
Supply voltage (VIN) ..................... 2.7V to 16V(4)
Output voltage (VOUT) ......................... 0.8V to 6V
EN current (IEN) ....................................... 100μA
Operating junction temp. (TJ). .. -40°C to +125°C
MP2276 Rev.1.1
5/30/2018
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3
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
VIN = 12V, TJ = -40°C to +125°C (5), typical value is tested at TJ = +25°C, unless otherwise noted.
Parameters
VIN Supply Current
Supply current (shutdown)
Supply current (quiescent)
MOSFETs
HS switch on resistance
LS switch on resistance
Current Limit
Current limit threshold
IILIM to IOUT ratio
Low-side negative current limit
Negative current limit timeout (6)
Timer
Switching frequency
Symbol
IIN
IIN
HSRDS-ON
LSRDS-ON
VLIM
IILIM/IOUT
Condition
Typ
Max
Units
VEN = 0V
VEN = 2V, VFB = 0.82V
0
600
1
μA
μA
VBST-SW = 3.3V
VCC = 3V
24
10
mΩ
mΩ
1.2
40
-4
80
V
μA/A
A
ns
IOUT ≥ 2A
36
FREQ/MODE = AGND
FREQ/MODE = 60.4kΩ to
AGND
900
1100
1300
kHz
530
600
790
kHz
50
180
ns
ns
121%
85%
VREF
VREF
ILIM NEG 10
tNCL Timer
fSW
Minimum on time (6)
TON MIN
(6)
Minimum off time
TOFF MIN
Over-Voltage (OVP) and Under-Voltage Protection (UVP)
OVP threshold
VOVP
UVP threshold
VUVP
Soft Start (SS)
CSS = 3.3nF, VOUT from
Soft-start time
tSS
10% to 90%
Error Amplifier (EA)
Feedback voltage
VFB
TA = 25°C
Enable (EN)
Enable input rising threshold
VIHEN
Enable hysteresis
VEN-HYS
Enable input current
IEN
VEN = 2V
Soft shutdown discharge FET
RON DISCH
VCC Regulator
VCC under-voltage lockout
VCCVth
threshold rising
VCC under-voltage lockout
VCCHYS
threshold hysteresis
VCC output voltage
VCC
VCC load regulation
ICC = 5mA
MP2276 Rev.1.1
5/30/2018
Min
111%
75%
116%
80%
44
1.7
ms
792
800
808
mV
1.15
1.21
220
0
80
1.27
V
mV
μA
Ω
2.65
2.8
2.95
V
280
mV
3.00
0.5
V
%
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4
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 12V, TJ = -40°C to +125°C (5), typical value is tested at TJ = +25°C, unless otherwise noted.
Parameters
Thermal Protection
Thermal shutdown (6)
Thermal shutdown hysteresis (6)
Power Good (PG)
Power good high threshold
Power good low threshold
Power good low to high delay
Power good sink current
capability
Power good leakage current
Symbol
Condition
Min
TSD
TSD HYS
PGVth Hi Rise
PGVth Lo Rise
PGVth Lo Fall
PGTd
VPG
IPG
LEAK
VOL_100
Power good low-level output
voltage
VOL_10
Typ
Max
150
20
FB from low to high
FB from low to high
FB from high to low
87.5%
111%
75%
0.7
92.5%
116%
80%
1.0
IPG = 10mA
VPG = 3V
VIN = 0V, pull PG up to
3.3V through a 100kΩ
resistor
VIN = 0V, pull PG up to
3.3V through a 10kΩ
resistor
650
Units
°C
°C
97.5%
121%
85%
1.3
VREF
VREF
VREF
ms
0.4
V
3
µA
900
mV
800
1050
NOTES:
5) Not tested in production, guaranteed by over-temperature correlation.
6) Guaranteed by engineering sample characterization.
MP2276 Rev.1.1
5/30/2018
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5
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL CHARACTERISTICS
VIN = 12V, VOUT = 1V, L = 1µH, FSW = 600kHz, pulse-skip mode, TA = +25°C, unless otherwise
noted.
Efficiency vs. Output Current
Efficiency vs. Output Current
VOUT = 1.2V, L = 1µH (DCR = 4.6mΩ)
100
100
90
90
80
80
Efficiency(%)
Efficiency(%)
VOUT = 1V, L = 1µH (DCR = 4.6mΩ)
70
60
Vin=5V
Vin=12V
Vin=16V
50
40
70
60
Vin=5V
Vin=12V
Vin=16V
50
40
0.01
0.10
1.00
Output Current(A)
10.00
0.01
VOUT = 1.8V, L = 1.5µH (DCR = 4.3mΩ)
VOUT = 2.5V, L = 1.5µH (DCR = 4.3mΩ)
100
100
90
95
90
80
Efficiency(%)
Efficiency(%)
10.00
Efficiency vs. Output Current
Efficiency vs. Output Current
70
60
Vin=5V
Vin=12V
Vin=16V
50
40
85
80
75
Vin=5V
Vin=12V
Vin=16V
70
65
60
0.01
0.10
1.00
Output Current(A)
10.00
0.01
Efficiency vs. Output Current
95
95
90
90
Efficiency(%)
100
85
80
75
MP2276 Rev.1.1
5/30/2018
0.10
1.00
Output Current(A)
80
75
Vin=9V
Vin=12V
Vin=16V
65
60
60
0.01
85
70
Vin=5V
Vin=12V
Vin=16V
65
10.00
VOUT = 5V, L = 2.2µH (DCR = 11.4mΩ)
100
70
0.10
1.00
Output Current(A)
Efficiency vs. Output Current
VOUT = 3.3V, L = 2.2µH (DCR = 11.4mΩ)
Efficiency(%)
0.10
1.00
Output Current(A)
10.00
0.01
0.10
1.00
Output Current(A)
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6
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL CHARACTERISTICS (continued)
VIN = 12V, VOUT = 1V, L = 1µH, FSW = 600kHz, pulse-skip mode, TA = +25°C, unless otherwise
noted.
Line Regulation
0.10
0.1
0.06
0.06
Line Regulation(%)
Load Regulation(%)
Load Regulation
0.02
‐0.02
Vin=5V
Vin=12V
Vin=16V
‐0.06
0.02
‐0.02
Iout = 0.01 A
Iout = 4 A
Iout = 8 A
‐0.06
‐0.1
‐0.10
0
1
2
3
4
5
6
7
4
8
Output Current(A)
Case Temperature Rise
vs. Output Current
4-Layer PCB, Size is 7.75cmx8.13cm
Forced CCM, No Load
Frequency (kHz)
Case Temperature Rise (⁰C)
30
20
10
0
1
2
3
4
5
6
Output Current (A)
16
Switching Frequency
vs. Temperature
40
0
8
12
Input Voltage(V)
7
2400
2200
2000
1800
1600
1400
1200
1000
800
600
400
600kHz
1100kHz
2000kHz
‐40 ‐20
8
FB Voltage vs. Temperature
0 20 40 60 80 100 120 140
Ambient Temperature (˚C)
Enable Supply Current vs. Input
Voltage
800
830
750
Enable Supply Current (uA)
Feedback Voltage (mV)
VFB = 0.82V, VEN = 2V
840
820
810
800
790
780
770
760
700
650
600
550
500
450
400
‐40 ‐20
MP2276 Rev.1.1
5/30/2018
0 20 40 60 80 100 120 140
Ambience Temperature (˚C)
4
8
12
Input Voltage (V)
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7
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL CHARACTERISTICS (continued)
VIN = 12V, VOUT = 1V, L = 1µH, FSW = 600kHz, pulse-skip mode, TA = +25°C, unless otherwise
noted.
Disabled Supply Current
vs. Input Voltage
Efficiency vs. Output Current
VIN=3.3V, VCC=VIN, L=0.68µH (DCR=3.1mΩ)
VEN = 0V
200
100
150
EFFICIENCY (%)
Disable Supply Current (nA)
95
100
50
90
85
80
75
Vout=1V
Vout=1.2V
Vout=1.8V
Vout=2.5V
70
65
0
4
MP2276 Rev.1.1
5/30/2018
8
12
Input Voltage (V)
16
60
0.01
0.1
1
10
LOAD CURRENT (A)
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
Performance waveforms are tested on the evaluation board in the Design Example section.
VIN = 12V, VOUT = 1V, L = 1µH, FSW = 600kHz, pulse-skip mode, TA = +25°C, unless otherwise
noted.
Start-Up through Input Voltage
Shutdown through Input Voltage
IOUT = 0A
IOUT = 0A
CH1: VOUT
500mV/div.
CH1: VOUT
500mV/div.
CH2: VIN
10V/div.
CHR1: VPG
5V/div
CH3: VSW
10V/div.
CH4: IL
2A/div.
CHR1: VPG
5V/div
CH2: VIN
10V/div.
CH3: VSW
10V/div.
CH4: IL
2A/div.
1ms/div.
200ms/div.
Start-Up through Input Voltage
Shutdown through Input Voltage
IOUT = 8A
IOUT = 8A
CH1: VOUT
500mV/div.
CH1: VOUT
500mV/div.
CH2: VIN
10V/div.
CHR1: VPG
5V/div
CH3: VSW
10V/div.
CH4: IL
10A/div.
CH2: VIN
10V/div.
CHR1: VPG
5V/div.
CH3: VSW
5V/div.
CH4: IL
10A/div.
1ms/div.
100µs/div.
Start-Up through Enable
Shutdown through Enable
IOUT = 0A
IOUT = 0A
CH1: VOUT
500mV/div.
CH1: VOUT
500mV/div.
CHR1: VPG
5V/div.
CH2: VEN
5V/div.
CH3: VSW
10V/div.
CH4: IL
2A/div.
CHR1: VPG
5V/div.
CH2: VEN
5V/div.
CH3: VSW
10V/div.
CH4: IL
1A/div.
1ms/div.
MP2276 Rev.1.1
5/30/2018
5ms/div.
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Performance waveforms are tested on the evaluation board in the Design Example section.
VIN = 12V, VOUT = 1V, L = 1µH, FSW = 600kHz, pulse-skip mode, TA = +25°C, unless otherwise
noted.
Start-Up through Enable
Shutdown through Enable
IOUT = 8A
IOUT = 8A
CH1: VOUT
500mV/div.
CHR1: VPG
5V/div
CH2: VEN
5V/div.
CH3: VSW
10V/div.
CH4: IL
10A/div.
CH1: VOUT
500mV/div.
CHR1: VPG
5V/div
CH2: VEN
5V/div.
CH3: VSW
10V/div.
CH4: IL
10A/div.
1ms/div.
20µs/div.
Input/Output Ripple
Input/Output Ripple
IOUT = 0A
IOUT = 8A
CH1:
VOUT/AC
50mV/div.
CH1:
VOUT/AC
50mV/div.
CH2: VIN/AC
50mV/div.
CH2:
VIN/AC
100mV/div.
CH3: VSW
10V/div.
CH3: VSW
10V/div.
CH4: IL
2A/div.
CH4: IL
5A/div.
20ms/div.
1µs/div.
Transient Response
Short-Circuit Entry
IOUT = 4A - 8A, Slew Rate = 2.5A/µs by Eload
IOUT = 0A
CH1:
VOUT/AC
50mV/div.
CH1: VOUT
1V/div.
CH2: VPG
5V/div.
CH3: VSW
10V/div.
CH4: IOUT
2A/div.
CH4: IL
10A/div.
100µs/div.
MP2276 Rev.1.1
5/30/2018
10ms/div.
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Performance waveforms are tested on the evaluation board in the Design Example section.
VIN = 12V, VOUT = 1V, L = 1µH, FSW = 600kHz, pulse-skip mode, TA = +25°C, unless otherwise
noted.
Short-Circuit Recovery
IOUT = 0A
CH1: VOUT
1V/div.
CH2: VPG
5V/div.
CH3: VSW
10V/div.
CH4: IL
10A/div.
10ms/div.
MP2276 Rev.1.1
5/30/2018
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11
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
PIN FUNCTIONS
Pin #
1, 14
2, 11
3
4
5
6
7
8
9
10
12
13
MP2276 Rev.1.1
5/30/2018
Name
Description
System ground. PGND is the reference ground of the regulated output voltage.
PGND
PGND requires careful consideration during PCB layout. Connect using wide PCB
traces.
Switch output. Connect SW to the inductor and bootstrap capacitor. SW is driven
up to VIN by the high-side switch during the on-time of the PWM duty cycle. The
SW
inductor current drives SW negative during the off-time. Connect using wide PCB
traces.
Supply voltage. VIN supplies power to the internal MOSFET and regulator.
VIN
Decouple the input rail with an input capacitor. Connect using wide PCB traces and
multiple vias.
Current limit. Connect a resistor from ILIM to ground to set the current limit trip
ILIM
point.
Enable. EN is a digital input that turns the regulator on or off. Drive EN high to turn
on the regulator; drive EN low to turn off the regulator. Connect EN to VIN through
EN
a pull-up resistor or a resistive voltage divider for automatic start-up. Do not float
EN.
Feedback. An external resistor divider from the output to GND tapped to FB sets
FB
the output voltage. Place the resistor divider as close to FB as possible. Vias
should be avoided on the FB traces.
AGND
Analog ground. Select AGND as the control circuit reference point.
External tracking voltage input. The output voltage tracks this input signal.
Decouple SS/TRK with a ceramic capacitor as close to it as possible. Ceramic
SS/TRK
capacitors with X7R or X5R grade dielectrics are recommended for their stable
temperature characteristics. The capacitance of this capacitor determines the softstart time. See the Soft Start section on page 15 for details.
Power good output. PG is an open-drain signal. A pull-up resistor connected to a
PG
DC voltage is required to indicate high if the output voltage is within regulation.
There is a delay of about 1ms from the time FB ≥ 92.5% to PG pulling high.
Bootstrap. Connect a capacitor between SW and BST to form a floating supply
BST
across the high-side switch driver.
Operation mode selection. Program FREQ/MODE to select CCM or pulse-skip
FREQ/MODE
mode and the operating switching frequency. See Table 1 on page 15 for details.
Internal 3V LDO output. VCC supplies power to the driver and control circuits.
Decouple VCC with a minimum 1µF ceramic capacitor as close to it as possible.
VCC
Ceramic capacitors with X7R or X5R grade dielectrics are recommended for their
stable temperature characteristics.
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12
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
BLOCK DIAGRAM
Figure 1: Functional Block Diagram
MP2276 Rev.1.1
5/30/2018
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13
MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
OPERATION
Constant-On-Time (COT) Control
The MP2276 employs constant-on-time (COT)
control to achieve a fast load transient response.
Figure 2 shows details of the control stage of
the MP2276.
A dead short occurs between VIN and PGND if
both the HS-FET and the LS-FET are turned on
at the same time. This is called shoot-through.
To avoid shoot-through, a dead time (DT) is
generated internally between the HS-FET off
and the LS-FET on period or the LS-FET off
and the HS-FET on period.
The operational amplifier (AMP) corrects any
error voltage between FB and VREF. The
MP2276 can use AMP to provide excellent load
regulation over the entire load range, whether it
is operating in forced continuous conduction
mode (CCM) or pulse-skip mode.
The MP2276 has internal RAMP compensation
to support low ESR MLCC output capacitor
solutions. The adaptive internal RAMP is
optimized so that the MP2276 is stable in the
entire operating input/output voltage range with
a proper design of the output L/C filter.
Figure 3: Heavy-Load Operation (PWM)
Figure 2: COT Control
Pulse-Width Modulation (PWM) Operation
Figure 3 shows how the pulse-width modulation
(PWM) signal is generated. AMP corrects any
error between FB and REF and generates a
fairly smooth DC voltage (COMP). The internal
RAMP is superimposed onto COMP. The
superimposed COMP is compared with the FB
signal. Whenever FB drops below the
superimposed COMP, the integrated high-side
MOSFET (HS-FET) turns on and remains on for
a fixed turn-on time. The fixed on time is
determined by the input voltage, output voltage,
and selected switching frequency. After the on
period elapses, the HS-FET turns off. The HSFET turns on again when FB drops below the
superimposed COMP. By repeating this
operation, the MP2276 regulates the output
voltage. The integrated low-side MOSFET (LSFET) turns on when the HS-FET is in its off
state to minimize conduction loss.
MP2276 Rev.1.1
5/30/2018
Continuous
Conduction
Mode
(CCM)
Operation
Continuous conduction mode (CCM) occurs
when the output current is high and the inductor
current is always above zero amps (see Figure
3). The MP2276 can also be configured to
operate in forced CCM operation when the
output current is low. See the FREQ/MODE
Selection section on page 15 for details.
In CCM operation, the switching frequency is
fairly constant (PWM mode), so the output
ripple remains almost constant throughout the
entire load range.
Pulse-Skip Operation
At light-load condition, the MP2276 can be
configured to work in pulse-skip mode to
optimize efficiency. When the load decreases,
the inductor current decreases as well. Once
the inductor current reaches zero, the MP2276
transitions from CCM to pulse-skip mode if the
MP2276
is
configured
so.
See
the
FREQ/MODE Selection section on page 15 for
details.
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
Figure 4 shows pulse-skip mode operation at
light-load condition. When FB drops below the
superimposed COMP, the HS-FET turns on for
a fixed interval. When the HS-FET turns off, the
LS-FET turns on until the inductor current
reaches zero. In pulse-skip mode operation, FB
does not reach the superimposed COMP when
the inductor current approaches zero. The LSFET driver turns into tri-state (Hi-Z) when the
inductor current reaches zero. Therefore, the
output capacitors discharge slowly to PGND
through the FB resistors (R1 and R2). At lightload condition, the HS-FET is not turned on as
frequently in pulse-skip mode as it is in forced
CCM. As a result, the efficiency in pulse-skip
mode is improved greatly compared to that in
forced CCM operation.
The MP2276 enters PWM mode once the
output current exceeds the critical level.
Afterward, the switching frequency remains
fairly constant over the output current range.
The MP2276 can be configured to operate in
forced CCM even in light-load condition (see
Table 1).
FREQ/MODE Selection
The MP2276 provides both forced CCM
operation and pulse-skip operation in light-load
condition. The MP2276 has three options for
switching
frequency
selection:
600kHz,
1100kHz, and 2000kHz. Select the operation
mode under light-load condition and the
switching frequency by choosing the resistance
value of the resistor connected between MODE
and AGND or VCC (see Table 1).
Table 1: FREQ/MODE Selection
MODE
AGND
30.1kΩ (±20%)
to AGND
60.4kΩ (±20%)
to AGND
121kΩ (±20%)
to AGND
243kΩ (±20%)
to AGND
VCC
Figure 4: Pulse Skip in Light Load
As the output current increases from the lightload condition, the time period the current
modulator regulates in becomes shorter. The
HS-FET is turned on more frequently, and the
switching frequency increases accordingly. The
output current reaches the critical level when
the current modulator time is zero. The critical
level of the output current is determined with
Equation (1):
IOUT
( V VOUT ) VOUT
IN
2 L FSW VIN
(1)
Light-Load
Mode
Forced CCM
Switching
Frequency
1100kHz
Forced CCM
2000kHz
Forced CCM
600kHz
Pulse Skip
600kHz
Pulse Skip
2000kHz
Pulse Skip
1100kHz
Soft Start (SS)
The minimum soft-start time is limited to 1.7ms.
This can be increased by choosing the
capacitor between SS/TRK and AGND. A
minimum value of 3.3nF for this capacitor is
always required to stabilize the reference
voltage.
The capacitance of this capacitor can be
determined with Equation (2) and Equation (3):
C SS (nF ) 3.3 22
(tSS = 1.7ms) (2)
t ss (ms ) x10 A
0.8V
(tSS > 1.7ms) (3)
C SS (nF )
Where FSW is the switching frequency.
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
Output Voltage External Reference
SS/TRK can be used as an analog input pin to
accept an external reference. When an external
voltage signal is connected to SS/TRK, it acts
as a reference for the MP2276 output voltage.
The FB voltage (VFB) follows this external
voltage signal exactly. The soft-start settings
are ignored. The SS/TRK input signal can be in
the range of 0.3V to 1.4V. During the initial
start-up, SS/TRK must first reach 800mV or
above to ensure proper operation. Afterward,
SS/TRK can be any value between 0.3V and
1.4V. If the external reference is added before
start-up, it should be no more than 1.2V to
avoid triggering under-voltage protection (UVP).
Pre-Bias Start-Up
The MP2276 is designed for monotonic start-up
into pre-biased loads. If the output is pre-biased
to a certain voltage during start-up, the IC
disables switching for both the high-side and
low-side switches until the internal soft-start
voltage exceeds the sensed output voltage at
FB.
Output Voltage Discharge
When the MP2276 is disabled through EN, the
output voltage discharge mode is enabled. Both
the HS-FET and the LS-FET are latched off. A
discharge MOSFET connected between SW
and GND is turned on to discharge the output
voltage. The typical switch on resistance of this
MOSFET is about 80Ω. Once VFB drops below
10% of VREF, the discharge MOSFET is turned
off.
Current Sense and Over-Current Protection
(OCP)
The MP2276 features an on-die current sense
and programmable positive current limit
threshold. The current limit is active when the
MP2276 is enabled. During the LS-FET on
state, the SW current (inductor current) is
sensed and mirrored to ILIM with the ratio of
GCS. By using a resistor (RILIM) from ILIM to
AGND, the ILIM voltage (VILIM) is proportional to
the SW cycle-by-cycle current. The HS-FET is
only allowed to turn on whenever VILIM is below
the internal over-current protection (OCP)
voltage threshold (VOCP) during the LS-FET on
state to limit the SW ripple valley current cycleby-cycle.
RILIM with Equation (4):
RILIM ( )
GCS (ILIM
VOCP
(VIN VO ) VO
1
)
VIN
2 L fs
(4)
Where VOCP is 1.2V, GCS is 40µA/A, and ILIM is
the desired output current limit (A).
During an over-current condition, the average
inductor current is less than the output load
current, and the output capacitor must supply
the extra current. Eventually, the output voltage
drops. Once the output voltage drops to the
under-voltage protection (UVP) threshold, the
MP2276 enters hiccup mode to restart the part
periodically. If the MP2276 detects an overcurrent condition for 31 consecutive cycles,
even if the output voltage is above the UVP
level, it enters hiccup mode. The average shortcircuit current is reduced greatly to alleviate the
thermal issue and protect the regulator. The
MP2276 exits hiccup mode once the undervoltage (UV) condition is removed.
Negative Inductor Current Limit
When LS-FET detects a -4A current, the
MP2276 turns off the LS-FET for 80ns to limit
the negative current.
Under -Voltage Protection (UVP)
The MP2276 monitors the output voltage by
connecting FB to the tap of a resistor divider to
detect an under-voltage condition. If VFB drops
below 80% of VREF, under-voltage protection
(UVP) is triggered. The MP2276 enters hiccup
protection mode to restart the part periodically.
The MP2276 exits UVP when VFB recovers to
more than 92.5% of VREF.
Output Sinking Mode (OSM)
The MP2276 uses output sinking mode (OSM)
to regulate the output voltage to the targeted
value. When VFB is above 105% of VREF, but is
below the OVP threshold, OSM is triggered.
During OSM operation, the LS-FET remains on
until it reaches the -4A negative current limit.
After hitting -4A, the LS-FET is turned off
momentarily for 80ns and is then turned on
again. The MP2276 continues this operation
until VFB drops below 102.5% of VREF. Once it
does, the MP2276 exits OSM after 15
consecutive cycles of forced CCM.
Calculate the current limit threshold setting from
MP2276 Rev.1.1
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
Over-Voltage Protection (OVP)
The MP2276 monitors the output voltage using
FB connected to the tap of a resistor divider to
detect an over-voltage condition. If VFB exceeds
116% of VREF, OVP is triggered. The controller
enters a dynamic regulation period. During this
period, the low-side negative current limit
increases to -8A. The LS-FET remains on until
it triggers the low-side negative current limit.
After hitting the low-side negative current limit,
the LS-FET is turned off momentarily for 80ns
and is then turned on again. This discharges
the output to keep it within the normal range.
The MP2276 exits this regulation period when
VFB falls below 102.5% of VREF.
Over-Temperature Protection (OTP)
The MP2276 has over-temperature protection
(OTP). The IC monitors the junction
temperature
internally.
If
the
junction
temperature exceeds the threshold value
(typically 150°C), the converter shuts off. There
is a hysteresis of about 20°C. Once the junction
temperature drops to about 130°C, soft start is
initiated.
Power Good (PG)
The MP2276 has a power good (PG) output.
PG is the open drain of a MOSFET. Connect
PG to VCC or another external voltage source
less than 3.6V through a pull-up resistor
(typically 100kΩ). After applying the input
voltage, the MOSFET turns on so that PG is
pulled to GND before the internal soft-start
voltage is ready. After VFB reaches 92.5% of
VREF, PG is pulled high after a 1ms delay.
When VFB drops to 80% of VREF (UV) or
exceeds 116% of VREF (OV), PG is pulled low.
Once VFB rises back to its nominal voltage
window (rises to 92.5% of VREF for UV, drops to
102.5% of VREF for OV), PG goes high again.
If the input supply fails to power the MP2276,
PG is pulled low, even though it is tied to an
external DC source through a pull-up resistor.
The relationship between the PG voltage and
the pull-up current is shown in Figure 5.
Figure 5: PG Clamped Voltage vs. Pull-Up
Current
Enable (EN) Configuration
The MP2276 turns on when EN goes high. The
MP2276 turns off when EN goes low. EN
cannot be left floating for proper operation. EN
can be driven by an analog or digital control
logic signal to enable or disable the MP2276.
EN is clamped internally using a 4V series
Zener diode (see Figure 6). Connect the EN
input through a pull-up resistor to VIN to limit
the EN input current to less than 100μA to
prevent damage to the Zener diode. For
example, if connecting a 300kΩ pull-up resistor
to 16VIN, then IZener = (16V - 4V) / 300kΩ =
40µA.
The MP2276 provides accurate EN thresholds,
so a resistor divider from VIN to AGND can be
used to program the input voltage at which the
MP2276
is
enabled.
This
is
highly
recommended for applications where there is
no dedicated EN control logic signal to avoid
possible UVLO bouncing during power-up and
power-down. The resistor divider values can be
determined with Equation (5):
VIN _ START ( V ) VIHEN
R UP R DOWN
R DOWN
(5)
Where VIHEN is 1.21V, typically. RUP and RDOWN
should be chosen to limit the EN input current
below 100μA.
Figure 6: Zener Diode between EN and GND
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
APPLICATION INFORMATION
Output Voltage Setting
Choose a proper value for R1 in the range of
1kΩ to 100kΩ. Then determine R2 with
Equation (6):
R2 (k)
VREF
R1(k)
VO VREF
(6)
To optimize the load transient response, a feedforward capacitor (CFF) is needed in parallel
with R1. R1 and CFF form an extra zero to the
system, which helps improve loop responses.
R1 and CFF are chosen so that the zero is
located around 20kHz - 60kHz.
Table 2 lists the recommended resistor values
for common output voltages.
Table 2: Resistor Selection for Common Output
Voltages (6)
VOUT(V)
R1(kΩ)
R2(kΩ)
1
2
8.06
1.2
2
4.02
1.8
10
8.06
2.5
10
4.7
3.3
10
3.16
5
10
1.91
NOTE:
5) For additional component parameters, please refer to the
Typical Application Circuits on page 21 to page 22.
Selecting the Input Capacitor
The input current to the step-down converter is
discontinuous and therefore requires a
capacitor to supply AC current to the step-down
converter while maintaining the DC input
voltage. Use ceramic capacitors for the best
performance. During layout, place the input
capacitors as close to VIN as possible.
The capacitance can vary significantly with the
temperature. Capacitors with X5R and X7R
ceramic dielectrics are recommended because
they are fairly stable over a wide temperature
range.
The capacitors must also have a ripple current
rating that exceeds the converter’s maximum
input ripple current. Estimate the input ripple
current with Equation (7):
ICIN IOUT
MP2276 Rev.1.1
5/30/2018
VOUT
V
(1 OUT )
VIN
VIN
The worst-case condition occurs at VIN = 2VOUT,
shown in Equation (8):
I
(8)
ICIN OUT
2
For simplification, choose an input capacitor
with an RMS current rating that exceeds half
the maximum load current.
The input capacitance value determines the
converter input voltage ripple. Select a
capacitor value that meets any input voltage
ripple requirement.
Estimate the input voltage ripple with Equation
(9):
VIN
IOUT
V
V
OUT (1 OUT )
FSW CIN
VIN
VIN
(9)
The worst-case condition occurs at VIN = 2VOUT,
shown in Equation (10):
IOUT
1
VIN
(10)
4 FSW CIN
Selecting the Output Capacitor
The output capacitor maintains the DC output
voltage. Use ceramic capacitors or POSCAPs.
Estimate the output voltage ripple with Equation
(11):
VOUT
VOUT
V
1
) (11)
(1 OUT ) (R ESR
8 FSW C OUT
FSW L
VIN
When
using
ceramic
capacitors,
the
capacitance dominates the impedance at the
switching frequency. The capacitance also
dominates the output voltage ripple. For
simplification, estimate the output voltage ripple
with Equation (12):
VOUT
VOUT
2
8 FSW L COUT
(1
VOUT
) (12)
VIN
For POSCAPs, the ESR dominates the
switching
frequency
impedance.
For
simplification, the output ripple can be
approximated with Equation (13):
VOUT
VOUT
V
(1 OUT ) RESR
FSW L
VIN
(13)
(7)
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
Selecting the Inductor
The inductor supplies a constant current to the
output load while being driven by the switching
input voltage. A larger-value inductor results in
less ripple current and lower output ripple
voltage, but also has a larger physical size,
higher series resistance, and lower saturation
current. Generally, select an inductor value that
allows the inductor peak-to-peak ripple current
to be 30% to 40% of the maximum switch
current limit. Also design for a peak inductor
current that is below the maximum switch
current limit. Calculate the inductance value
with Equation (14):
L
VOUT
V
(1 OUT )
FSW IL
VIN
PCB Layout Guidelines
Efficient PCB layout is critical for stable
operation. For the best performance, refer to
Figure 7 and follow the guidelines below.
1. Place the input MLCC capacitors as close to
VIN and PGND as possible.
2. Place the major MLCC capacitors on the
same layer as the MP2276.
3. Maximize the VIN and PGND copper plane
to minimize parasitic impedance.
4. Place as many PGND vias as possible as
close to the MP2276 as possible to
minimize both parasitic impedance and
thermal resistance.
(14)
5. Place a VCC decoupling capacitor close to
the device.
Where ∆IL is the peak-to-peak inductor ripple
current.
6. Connect AGND and PGND at the point of
the VCC capacitor's ground connection.
Choose an inductor that will not saturate under
the maximum inductor peak current. The peak
inductor current can be calculated with
Equation (15):
ILP IOUT
VOUT
V
(1 OUT )
2 FSW L
VIN
7. Place a BST capacitor as close to BST and
SW as possible.
8. Use a trace width of 20 mils or higher to
route the path.
(15)
9. Use a 1µF bootstrap capacitor.
13
PGND 1
12
FREQ/
MODE
SW 2
11
SW
VIN 3
10 BST
ILIM 4
9 PG
C4
C1A
C1
14
C3
VCC
PGND
L1
8 SS/TRK
EN 5
6
7
FB
AGND
R2
C5
R1
C6
Figure 7: Recommended Layout
MP2276 Rev.1.1
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
Design Example
Table 3 shows a design example following the
application guidelines for the specifications
below.
Table 3: Design Example
3.3V, 12V
VIN
1V
VOUT
8A
IO
The detailed application schematics are shown
in Figure 8 through Figure 17. The typical
performance and circuit waveforms are shown
in the Typical Performance Characteristics
section. For more device applications, please
refer to the related evaluation board datasheets.
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS
Figure 8: VIN = 4V - 16V, VOUT = 1V, IOUT = 8A, FSW = 600kHz
Figure 9: VIN = 4V - 16V, VOUT = 1.2V, IOUT = 8A, FSW = 600kHz
Figure 10: VIN = 4V - 16V, VOUT = 1.8V, IOUT = 8A, FSW = 600kHz
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS (continued)
Figure 11: VIN = 4V - 16V, VOUT = 2.5V, IOUT = 8A, FSW = 600kHz
Figure 12: VIN = 4.5V - 16V, VOUT = 3.3V, IOUT = 8A, FSW = 600kHz
Figure 13: VIN = 6V - 16V, VOUT = 5V, IOUT = 8A, FSW = 600kHz
MP2276 Rev.1.1
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS (continued)
Figure 14: VIN = 3.3V, VOUT = 1V, IOUT = 8A, FSW = 600kHz
Figure 15: VIN = 3.3V, VOUT = 1.2V, IOUT = 8A, FSW = 600kHz
Figure 16: VIN = 3.3V, VOUT = 1.8V, IOUT = 8A, FSW = 600kHz
MP2276 Rev.1.1
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS (continued)
Figure 17: VIN = 3.3V, VOUT = 2.5V, IOUT = 8A, FSW = 600kHz
MP2276 Rev.1.1
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MP2276 – 16V, 8A, HIGH EFFICIENCY, SYNC, STEP-DOWN CONVERTER
PACKAGE INFORMATION
QFN-14 (2mmx3mm)
NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. Users should
warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application.
MPS will not assume any legal responsibility for any said applications.
MP2276 Rev.1.1
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