MPS MPQ2314 High efficiency 2a, 24v, 500khz synchronous step down converter Datasheet

MPQ2314
High Efficiency 2A, 24V, 500kHz
Synchronous Step Down Converter
The Future of Analog IC Technology
DESCRIPTION
FEATURES
The MPQ2314 is a high frequency synchronous
rectified step-down switch mode converter with
built in internal power MOSFETs. It offers a
very compact solution to achieve 2A continuous
output current over a wide input supply range
with excellent load and line regulation. The
MPQ2314 has synchronous mode operation for
higher efficiency over output current load range.



Current mode operation provides fast transient
response and eases loop stabilization.
Full protection features include OCP and
thermal shut down.
The MPQ2314 requires a minimum number of
readily available standard external components
and is available in a space saving 8-pin
TSOT23 package.










Wide 4.5V to 24V Operating Input Range
2A Load Current
120mΩ/50mΩ Low Rds(on) Internal Power
MOSFETs
Low Quiescent Current
High
Efficiency
Synchronous
Mode
Operation
Fixed 500kHz Switching Frequency
Frequency Sync from 200kHz to 2MHz
External Clock
AAM Power Save Mode
Internal Soft Start
OCP Protection and Hiccup
Thermal Shutdown
Output Adjustable from 0.8V
Available in an 8-pin TSOT-23 package
APPLICATIONS



Notebook Systems and I/O Power
Digital Set Top Boxes
Flat Panel Television and Monitors
All MPS parts are lead-free, halogen free, and adhere to the RoHS
directive. For MPS green status, please visit MPS website under Quality
Assurance.
“MPS” and “The Future of Analog IC Technology” are Registered
Trademarks of Monolithic Power Systems, Inc.
TYPICAL APPLICATION
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
1
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
ORDERING INFORMATION
Part Number*
MPQ2314GJ
Package
TSOT23-8
Top Marking
See Blow
* For Tape & Reel, add suffix –Z (e.g. MPQ2314GJ–Z);
TOP MARKING
AELY
AEL: product code of MPQ2314GJ;
Y: year code;
PACKAGE REFERENCE
TOP VIEW
AAM
1
8
FB
IN
2
7
VCC
SW
3
6
EN/SYNC
GND
4
5
BST
TSOT23-8
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
2
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
ABSOLUTE MAXIMUM RATINGS (1)
Thermal Resistance
VIN ................................................–0.3V to +28V
VSW ...... –0.3V (-5V<10ns) to +28V ( 30V <10ns)
VBST ........................................................ VSW+6V
All Other Pins ..................................-0.3V to +6V
(2)
Continuous Power Dissipation (TA=+25°C) ...
................................................................. 1.25W
Junction Temperature ...............................150°C
Lead Temperature ....................................260°C
Storage Temperature................. -65°C to 150°C
TSOT23-8…………………...……100…..55..°C/W
Recommended Operating Conditions
(3)
Supply Voltage VIN ............................. 4.5 to 24V
Output Voltage VOUT .......................0.8V to VIN*D
Operating Junction Temp (TJ).. -40°C to +125°C
(4)
θJA
θJC
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 will cause excessive die temperature, and the
regulator will go into thermal shutdown. Internal thermal
shutdown circuitry protects the device from permanent
damage.
3) The device is not guaranteed to function outside of its
operating conditions.
4) Measured on JESD51-7, 4-layer PCB.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
3
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (5)
VIN = 12V, TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TJ = +25°C.
Parameter
Symbol
Supply
Current(Shutdown)
IIN
Supply
Current(Quiescent)
Iq
Condition
Min
VEN=0V,TJ=+25°C
Typ
Max
Units
0.03
1
μA
5
μA
240
μA
VEN=0V
VEN=2V, VFB=1V, AAM=0.5V
130
180
HS Switch On resistance
HSRDS-ON
VBST-SW=5V
120
mΩ
LS Switch On resistance
LSRDS-ON
VCC=5V
50
mΩ
Switch leakage
SWLKG
VEN=0V, VSW=12V
Current Limit
ILMIT
Duty Cycle=40%
Oscillator Frequency
fsw
Fold-back Frequency
fFB
VFB=200mV
Maximum Duty Cycle
DMAX
VFB=750mV
Minimum On Time(5)
TON_MIN
Sync Frequency Range
fSYNC
Feedback Voltage
VFB
Feedback Current
IFB
EN Rising Threshold
VEN_RISING
EN Falling Threshold
VEN_FALING
EN Hysteresis
EN Input Current
0.01
3
4
VFB=750mV, TJ=+25°C
420
500
VFB=750mV
380
90
0.779
TJ=+25°C
1.2
1.1
IEN
VIN Under Voltage
Lockout Threshold-Rising
VEN=2V
ENTd-off
INUVRISING
620
kHz
60
ns
2
MHz
0.803
V
0.807
V
10
50
nA
1.4
1.6
V
1.7
V
0.791
1.25
1.4
1.5
150
TJ=25°C
1.5
TJ=-40°C to 125°C
1.2
VEN=0
EN Turn Off Delay
kHz
%
1
VEN_HYS
620
95
1.1
TJ=+25°C
A
fsw
0.775
VFB=820mV
TJ=+25°C
μA
0.5
0.2
TJ=+25°C
1
2
mV
2.5
2.8
μA
5
50
nA
6
10
14
us
3.7
3.9
4.1
V
4.2
V
3.6
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
4
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (5)
VIN = 12V, TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TJ = +25°C.
Parameter
Symbol
VIN Under Voltage
Lockout Threshold-Falling
VIN Under Voltage
Lockout ThresholdHysteresis
VCC Regulation
INUVFALLING
Condition
Min
Typ
Max
Units
TJ=+25°C
2.9
3.2
3.5
V
3.6
V
2.8
INUVHYS
VCC
650
ICC=0 to 5mA
4.6
VCC Load Regulation
ICC =0 to 5mA
Soft-Start Period
VOUT from 10% to 90%,
TJ=+25°C
0.8
VOUT from 10% to 90%
0.5
Thermal Shutdown
TSS
(5)
Thermal Hysteresis(5)
AAM Source Current
IAAM
TJ=+25°C
5.6
mV
4.9
5.15
V
1
3
%
1.5
2.2
ms
2.6
ms
150
°C
20
°C
6.2
4
6.8
μA
8
μA
Notes:
5) Derived from bench characterization. Not tested in production.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
5
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
TYPICAL CHARACTERISTICS
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
6
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
TYPICAL CHARACTERISTICS (continued)
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
7
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
TYPICAL CHARACTERISTICS (continued)
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
8
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 19V, VOUT = 5V, L = 6.5uH, TA = 25°C, unless otherwise noted.
VOUT/AC
20mV/div.
VOUT/AC
20mV/div.
VIN/AC
200mV/div.
VIN/AC
500mV/div.
VSW
10V/div.
VSW
10V/div.
IL
2A/div.
IL
1A/div.
IL
2A/div.
VOUT
2V/div.
VOUT
2V/div.
VIN
10V/div.
VOUT
2V/div.
VIN
10V/div.
VSW
10V/div.
VOUT
2V/div.
VIN
10V/div.
VSW
10V/div.
VSW
10V/div.
VIN
10V/div.
VSW
10V/div.
IL
1A/div.
IL
2A/div.
IL
1A/div.
VOUT
2V/div.
VEN
5V/div.
VOUT
2V/div.
VEN
5V/div.
VSW
10V/div.
VSW
10V/div.
VSW
10V/div.
IL
2A/div.
IL
5A/div.
IL
2A/div.
VOUT
2V/div.
VEN
5V/div.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
9
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
VIN = 19V, VOUT = 5V, L = 6.5µH, TA = 25°C, unless otherwise noted.
VOUT
2V/div.
VEN
5V/div.
VOUT/AC
50mV/div.
VSW
10V/div.
IL
1A/div.
IO
1A/div.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
10
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
PIN FUNCTIONS
Package
Pin #
1
2
3
4
5
6
7
8
Name
Description
A resistor is connected from AAM pin to ground to set a AAM voltage force MPQ2314 into
non-synchronous mode when load is small. Drive AAM pin high (=VCC) will force
MPQ2314 into CCM.
Supply Voltage. The MPQ2314 operates from a +4.5V to +24V input rail. C1 is needed to
IN
decouple the input rail. Use wide PCB trace to make the connection.
SW
Switch Output. Use wide PCB trace to make the connection.
System Ground. This pin is the reference ground of the regulated output voltage.
GND
For this reason care must be taken in PCB layout. Suggested to be connected to GND with
copper and vias.
Bootstrap. A capacitor and a 20Ω resistor connected between SW and BST pins are
BST
required to form a floating supply across the high-side switch driver.
EN=1 to enable the MPQ2314. External clock can be applied to EN pin for changing
EN/SYNC
switching frequency.
Bias Supply. Decouple with 0.1μF-0.22μF cap. And the capacitance should be no more
VCC
than 0.22μF
Feedback. An external resistor divider from the output to GND, tapped to the FB pin, sets
the output voltage. To prevent current limit run away during a short circuit fault condition
FB
the frequency fold-back comparator lowers the oscillator frequency when the FB voltage is
below 400mV.
AAM
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
11
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
FUNCTION BLOCK DIAGRAM
Figure 1: Functional Block Diagram
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
12
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
OPERATION
The MPQ2314 is a high frequency synchronous
rectified step-down switch mode converter with
built in internal power MOSFETs. It offers a
very compact solution to achieve 2A continuous
output current over a wide input supply range
with excellent load and line regulation.
The MPQ2314 operates in a fixed frequency,
peak current control mode to regulate the
output voltage. A PWM cycle is initiated by the
internal clock. The integrated high-side power
MOSFET is turned on and remains on until its
current reaches the value set by the COMP
voltage. When the power switch is off, it
remains off until the next clock cycle starts. If, in
95% of one PWM period, the current in the
power MOSFET does not reach the COMP set
current value, the power MOSFET will be
forced to turn off.
Internal Regulator
Most of the internal circuitries are powered from
the 5V internal regulator. This regulator takes
the VIN input and operates in the full VIN range.
When VIN is greater than 5.0V, the output of
the regulator is in full regulation. When VIN is
lower than 5.0V, the output decreases, a 0.1uF
ceramic capacitor for decoupling purpose is
required.
Error Amplifier
The error amplifier compares the FB pin voltage
with the internal 0.8V reference (REF) and
outputs a COMP voltage, which is used to
control the power MOSFET current. The
optimized internal compensation network
minimizes the external component counts and
simplifies the control loop design.
AAM Operation
The
MPQ2314
has
AAM
(Advanced
Asynchronous Modulation) power-save mode
for light load. Connect a resistor from AAM pin
to GND to set AAM voltage. Under the heavy
load condition, the VCOMP is higher than VAAM.
When the clock goes high, the high-side power
MOSFET turns on and remains on until VILsense
reaches the value set by the COMP voltage.
The internal clock resets every time when VCOMP
is higher than VAAM.
Under the light load condition, the value of
VCOMP is low. When VCOMP is less than VAAM and
VFB is less than VREF, VCOMP ramps up until it
exceeds VAAM. During this time, the internal
clock is blocked, thus the MPQ2314 skips some
pulses for PFM (Pulse Frequency Modulation)
mode and achieves the light load power save.
Clock
1.1pF
Q
S
50pF
400k
R1
20k
R
R2
Figure 2: Simplified AAM Control Logic
Enable/SYNC control
EN is a digital control pin that turns the
regulator on and off. Drive EN high to turn on
the regulator, drive it low to turn it off. There is
an internal 1MEG resistor from EN to GND thus
EN can be floated to shut down the chip. Also
EN pin voltage was clamped to around 6.5V by
an internal zener-diode. Please use large
enough pull up resistor connecting between VIN
and EN to limit the EN input current which
should be less than 100uA. Generally, around
100k resistor should be large enough for all the
applications.
The chip can be synchronized to external clock
range from 200kHz up to 2MHz through this pin
2ms right after output voltage is set, with the
internal clock rising edge synchronized to the
external clock rising edge. EN synchronize logic
high voltage should higher than 2V. EN
synchronize logic low voltage should lower than
400mV. EN logic high pulse width must less
than 1.6µs. Otherwise the internal clock may
come and turn on high side MOSFET again. EN
logic low pulse width must less than 6µs,
otherwise MPQ2314 may EN shutdown.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
13
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
Under-Voltage Lockout (UVLO)
Under-voltage lockout (UVLO) is implemented
to protect the chip from operating at insufficient
supply voltage. The MPQ2314 UVLO
comparator monitors the output voltage of the
internal regulator, VCC. The UVLO rising
threshold is about 3.9V while its falling
threshold is consistent 3.25V.
Internal Soft-Start
The soft start is implemented to prevent the
converter output voltage from overshooting
during start up. When the chip starts, the
internal circuitry generates a soft-start voltage
(SS) ramping up from 0V. The soft-start period
lasts until the voltage on the soft-start capacitor
exceeds the reference voltage of 0.8V. At this
point the reference voltage takes over. The softstart time is internally set to be around 1.5ms.
Over-Current-Protection and Hiccup
The MPQ2314 has cycle-by-cycle over current
limit when the inductor current peak value
exceeds the set current limit threshold.
Meanwhile, output voltage starts to drop until
FB is below the Under-Voltage (UV) threshold,
typically 50% below the reference. Once a UV
is triggered, the MPQ2314 enters hiccup mode
to periodically restart the part. This protection
mode is especially useful when the output is
dead-short to ground. The average short circuit
current is greatly reduced to alleviate the
thermal issue and to protect the regulator. The
MPQ2314 exits the hiccup mode once the over
current condition is removed.
Thermal Shutdown
Thermal shutdown is implemented to prevent
the chip from operating at exceedingly high
temperatures. When the silicon die temperature
is higher than 150°C, it shuts down the whole
chip. When the temperature is lower than its
lower threshold, typically 130°C, the chip is
enabled again.
Floating Driver and Bootstrap Charging
The floating power MOSFET driver is powered
by an external bootstrap capacitor. This floating
driver has its own UVLO protection. This
UVLO’s rising threshold is 2.2V with a
hysteresis of 150mV. The bootstrap capacitor
voltage is regulated internally by VIN through
D1, R5, C5, L1 and C2 (Figure 3). If (VIN-VSW)
is more than 5V, U2 will regulate M3 to maintain
a 5V BST voltage across C5.
Figure 3: Internal Bootstrap Charging Circuit
Startup and Shutdown
If both VIN and EN are higher than their
appropriate thresholds, the chip starts. The
reference block starts first, generating stable
reference voltage and currents, and then the
internal regulator is enabled. The regulator
provides stable supply for the remaining
circuitries.
Three events can shut down the chip: EN low,
VIN low and thermal shutdown. In the shutdown
procedure, the signaling path is first blocked to
avoid any fault triggering. The COMP voltage
and the internal supply rail are then pulled down.
The floating driver is not subject to this
shutdown command.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
14
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
APPLICATION INFORMATION
COMPONENT SELECTION
Setting the Output Voltage
The external resistor divider is used to set the
output voltage (see Typical Application on page
1). The feedback resistor R1 also sets the
feedback loop bandwidth with the internal
compensation capacitor (see Typical Application
on page 1). R2 is then given by:
R1
R2 
VOUT
0.8V
1
The T-type network is highly recommended, as
Figure 4 shows.
FB
R1
RT
8
VOUT
R2
Figure 4: T-type Network
Table 1 lists the recommended T-type resistors
value for common output voltages.
Table 1—Resistor Selection for Common Output
Voltages
VOUT (V) R1 (kΩ)
R2 (kΩ) Rt (kΩ) Lo (µH)
Co(µF)
1.05
20.5
62
100
1.8
44
1.2
20.5
39.2
75
2.2
44
1.8
40.2
31.6
59
3.3
44
2.5
40.2
18.7
40.2
4.2
44
3.3
40.2
12.7
33
4.7
44
5
40.2
7.5
20
6.5
44
Selecting the Inductor
A 1µH to 10µH inductor with a DC current rating
of at least 25% percent higher than the maximum
load current is recommended for most
applications. For highest efficiency, the inductor
DC resistance should be less than 15mΩ. For
most designs, the inductance value can be
derived from the following equation.
L1 
Choose inductor current to be approximately
30% of the maximum load current. The maximum
inductor peak current is:
IL(MAX )  ILOAD 
I L
2
Under light load conditions below 100mA, larger
inductance is recommended for improved
efficiency.
Setting the AAM Voltage
The AAM voltage is used to setting the transition
point from AAM to CCM. It should be chosen to
provide the best combination of efficiency,
stability, ripple, and transient.
If the AAM voltage is set lower, then stability and
ripple improves, but efficiency during AAM mode
and transient degrades. Likewise, if the AAM
voltage is set higher, then the efficiency during
AAM and transient improves, but stability and
ripple degrades. So the optimal balance point of
AAM voltage for good efficiency, stability, ripple
and transient should be found out.
Adjust the AAM threshold by connecting a
resistor from AAM pin to ground. Take Figure 5
as reference. An internal 6.2µA current source
charges the external resistor.
Figure 5: AAM Network
Generally, R4 is then given by:
VAAM=R4 x 6.2uA
The optimized AAM can be got from Figure 6.
VOUT  (VIN  VOUT )
VIN  IL  fOSC
Where ΔIL is the inductor ripple current.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
15
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
0.7
prevent excessive voltage ripple at input. The
input voltage ripple caused by capacitance can
be estimated by:
0.6
0.5
VIN 
0.4
0.3
Selecting the Output Capacitor
0.2
0.1
0


ILOAD
V
V
 OUT   1  OUT 
fS  C1 VIN 
VIN 
0
2
4
6
8
Figure 6: AAM Selection for Common Output
Voltages (VIN=4.5V-24V)
VOUT 
Selecting the Input Capacitor
The input current to the step-down converter is
discontinuous, therefore a capacitor is required
to supply the AC current to the step-down
converter while maintaining the DC input
voltage. Use low ESR capacitors for the best
performance. Ceramic capacitors with X5R or
X7R dielectrics are highly recommended
because of their low ESR and small
temperature coefficients. For most applications,
a 22µF capacitor is sufficient.
Since the input capacitor (C1) absorbs the input
switching current it requires an adequate ripple
current rating. The RMS current in the input
capacitor can be estimated by:
I C1  ILOAD 
VOUT  VOUT
 1
VIN 
VIN
The output capacitor (C2) is required to
maintain the DC output voltage. Ceramic,
tantalum, or low ESR electrolytic capacitors are
recommended. Low ESR capacitors are
preferred to keep the output voltage ripple low.
The output voltage ripple can be estimated by:




Where L1 is the inductor value and RESR is the
equivalent series resistance (ESR) value of the
output capacitor.
In the case of ceramic capacitors, the
impedance at the switching frequency is
dominated by the capacitance. The output
voltage ripple is mainly caused by the
capacitance. For simplification, the output
voltage ripple can be estimated by:
ΔVOUT 
ILOAD
2
For simplification, choose the input capacitor
whose RMS current rating greater than half of
the maximum load current.
The input capacitor can be electrolytic, tantalum
or ceramic. When using electrolytic or tantalum
capacitors, a small, high quality ceramic
capacitor, i.e. 0.1μF, should be placed as close
to the IC as possible. When using ceramic
capacitors, make sure that they have enough
capacitance to provide sufficient charge to
 V 
VOUT
  1  OUT 
VIN 
8  fS  L1  C2 
2
In the case of tantalum or electrolytic capacitors,
the ESR dominates the impedance at the
switching frequency. For simplification, the
output ripple can be approximated to:
The worse case condition occurs at VIN =
2VOUT, where:
IC1 

VOUT  VOUT  
1
 1 

   RESR 
fS  L1 
VIN  
8  fS  C2 
ΔVOUT 
VOUT 
V
  1  OUT
fS  L1 
VIN

  RESR

The characteristics of the output capacitor also
affect the stability of the regulation system. The
MPQ2314 can be optimized for a wide range of
capacitance and ESR values.
External Bootstrap Diode
An external bootstrap diode may enhance the
efficiency of the regulator, the applicable
conditions of external BST diode are:
 VOUT is 5V or 3.3V; and

Duty cycle is high: D=
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
VOUT
>65%
VIN
16
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
GND
R1
C3
R3
R7
5
4
R5
6
7
2
3
8
R9
R6
SW
C4
1
R2
R4
R8
C5
C6
In these cases, an external BST diode is
recommended from the VCC pin to BST pin, as
shown in Figure 7.
L1
C8
C1
C 1A
Vin
C2
Figure 7: Add Optional External
PC Board Layout (6)
PCB layout is very important to achieve stable
operation. Please follow these guidelines and
take Figure 8 as reference.
1) Keep the connection of input ground and
GND pin as short and wide as possible.
C 2A
GND
Bootstrap Diode to Enhance Efficiency
The recommended external BST diode is
IN4148, and the BST cap is 0.1─1μF.
GND
VOUT
VCC
EN / SYNC
BST
SW
2) Keep the connection of input capacitor and
IN pin as short and wide as possible.
3) Ensure all feedback connections are short
and direct. Place the feedback resistors and
compensation components as close to the chip
as possible.
Vout
GND
4) Route SW away from sensitive analog areas
such as FB.
Notes:
6) The recommended layout is based on the Figure 9 Typical
Application circuit on the next page.
Figure 8: Sample Board Layout
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
17
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
Design Example
Below is a design example following the
application guidelines for the specifications:
Table 2: Design Example
VIN
VOUT
IO
19V
5V
2A
The detailed application schematics are shown
in Figures 9 through 14. The typical
performance and circuit waveforms have been
shown
in
the
Typical
Performance
Characteristics section. For more device
applications, please refer to the related
Evaluation Board Datasheets.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
18
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
TYPICAL APPLICATION CIRCUITS
Figure 9: Vo=5V, Io=2A
Figure 10: Vo=3.3V, Io=2A
Figure 11: Vo=2.5V, Io=2A
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
19
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
Figure 12: Vo=1.8V, Io=2A
Figure 13: Vo=1.2V, Io=2A
Figure 14: Vo=1.05V, Io=2A
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
20
MPQ2314 – 24V, 2A SYNC STEP DOWN CONVERTER
PACKAGE INFORMATION
TSOT23-8
NOTICE: The information in this document is subject to change without notice. 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.
MPQ2314 Rev. 1.1
www.MonolithicPower.com
6/10/2015
MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited.
© 2015 MPS. All Rights Reserved.
21
Similar pages