Microchip MIC23031-4YMT Bedienungsanleitung


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MIC23031 Evaluation Board
4MHz PWM 400mA Buck Regulator
with HyperLight Load®
HyperLight Load is a registered trademark of Micrel, Inc.
Micrel Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel +1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
June 17, 2014 Revision 2.0
General Description
The MIC23031 is a 400mA 4MHz switching regulator
featuring HyperLight Load® mode. The MIC23031 is
highly-efficient throughout the entire output current range,
drawing just 21µA of quiescent current in operation. The
tiny 1.6mm ï‚´ 1.6mm Thin DFN package in combination
with the 4MHz switching frequency enables a compact
sub-1mm height solution with only three external
components. The MIC23031 provides accurate output
voltage regulation under the most demanding conditions
responding extremely quickly to a load transient with
exceptionally small output voltage ripple.
Factoring in the output current, the internal circuitry of the
MIC23031 automatically selects between two modes of
operation for optimum efficiency. Under light-load
conditions, the MIC23031 goes into HyperLight Load
mode. HyperLight Load uses a pulse-frequency
modulation (PFM) control scheme that controls the off-time
at light load. This proprietary architecture reduces the
amount of switching needed at light loads, thereby
increasing operating efficiency. The MIC23031 attains up
to 88% efficiency at 1mA output load. As the load current
increases beyond approximately 100mA, the device
operates using the pulse-width modulation (PWM) method
for up to 93% efficiency at higher loads. The two modes of
operation ensure the highest efficiency across the entire
load range.
The MIC23031 operates from an input voltage range of
2.7V to 5.5V and features internal power MOSFETs that
deliver up to 400mA of output current. This step-down
regulator provides an output voltage accuracy of 2.5%
across the junction temperature range of  40 C to  125 C.
The MIC23031 is available in fixed or adjustable versions
supporting an output voltage as low as 0.7V.
Datasheets and support documentation are available on
Micrel’s web site at: www.micrel.com.
Requirements
The MIC23031 evaluation board requires an input power
source that is able to deliver greater than 500mA at 2.7V
to the MIC23031. The output load can either be an active
(electronic) or passive (resistive) load.
Getting Started
1. Connect an external supply to the VIN (J1)
terminal.
Apply the desired input voltage to VIN (J1) and ground
(J2) terminals of the evaluation board, paying careful
attention to polarity and supply voltage (2.7V ï‚£ VIN ï‚£
5.5V). An ammeter may be placed between the input
supply and the VIN (J1) terminal. Be sure to monitor
the supply voltage at the VIN (J1) terminal, since the
ammeter and/or power-lead resistance can reduce the
voltage supplied to the device.
2. Connect a load to the VOUT (J3) and ground
terminal (J4).
The load can be either passive (resistive) or active
(electronic) load. An ammeter may be placed between
the load and the output terminal. Ensure the output
voltage is monitored at the VOUT (J3) terminal.
3. Enable the MIC23031.
The MIC23031 evaluation board has a pull-up resistor
to VIN. To disable the device, apply a voltage below
0.5V to the EN (J5) terminal or place a jumper on JP1
to ground EN. In the absence of the pull-up resistor,
the device is enabled by applying a voltage greater
than 1.2V to the EN (J5) terminal. The EN pin must be
either pulled high or low for proper operation. Remove
the pull-up regulator to operate in an indeterminable
state.
Output Voltage
The MIC23031 evaluation board is available with the
output voltage options listed in the Ordering Information
table.
Ordering Information
Part Number Description
MIC23031-AYMT EV Adjustable-Output Evaluation Board
MIC23031-CYMT EV 1.0V Fixed-Output Evaluation Board
MIC23031-4YMT EV 1.2V Fixed-Output Evaluation Board
MIC23031-FYMT EV 1.5V Fixed-Output Evaluation Board
MIC23031-GYMT EV 1.8V Fixed-Output Evaluation Board
Note: Other voltage options available upon request.
Micrel, Inc.
MIC23031 Evaluation Board
Output Voltage (Adjustable Option Only)
The output voltage of the MIC23031 AYMT regulator is -
determined by feedback resistors R1 and R2 whose
values are calculated in Equation 1:





+×= 1
2R
1R
V62.0VOUT
Eq. 1
The output on the evaluation board is by default set to
1.8V (R1 = 383kΩ, R2 = 200kΩ), but can easily be
modified by removing R1 and replacing it with the value
that yields the desired output voltage.
2R1
V62.0
V
1R OUT ×




−=
Eq. 2
For optimum transient response performance, R2 should
be in the range of 180k to 220kΩ Ω.
HyperLight Load
MIC23031 uses a patented minimum on and off time
control loop at light loads. When the output voltage falls
below the lower regulation threshold, the error comparator
begins a switching cycle that turns the PMOS on and
keeps it on for the duration of the minimum on-time. This
increases the output voltage. Once the output voltage rises
to the higher regulation threshold, the error comparator
turns the PMOS off for a minimum off time until the output -
drops down to the lower threshold. The NMOS acts as an
ideal rectifier that conducts when the PMOS is off. Using a
NMOS switch instead of a diode reduces power dissipation
as current is sourced from ground. In discontinuous mode,
the MIC23031 works in PFM to regulate the output. As the
output current increases, the off time decreases, - therefore
more energy is delivered to the output. This switching
scheme improves the efficiency of the MIC23031 during
light load currents by activating the power FETs only as
needed. As the load current increases, the MIC23031
goes into continuous conduction mode (CCM) and
switches at a frequency centered at 4MHz. Equation 3
calculates the load where the MIC23031 goes into
continuous-conduction mode:
( )






×
×−
>fL2
DVV
IOUTIN
LOAD
Eq. 3
As shown in Equation 3, the load at which the MIC23031
transitions from HyperLight Load mode to PWM mode is a
function of the input voltage (VIN), output voltage (VOUT),
duty cycle (D), inductance (L), and frequency (f) (Figure 1).
Suitable inductors for the MIC23031 range from 0.47µH to
4.7µH. The device may be tailored to enter HyperLight
Load mode or PWM mode at a specific load current by
selecting the appropriate inductor. For example, if a 4.7µH
inductor is selected in a 3.6VIN to 1.8VOUT application,
the MIC23031 will transition into PWM mode at a load of
approximately 5mA. If, under the same conditions, a 1µH
inductor is chosen, the MIC23031 will transition into PWM
mode at approximately 70mA.
Figure 1. MIC23031 SW Frequency vs. Output Current
June 17, 2014 2 Revision 2.0
Micrel, Inc.
MIC23031 Evaluation Board
MIC23031 Typical Application Circuit (Fixed)
Bill of Materials
Item Part Number Manufacturer Description Qty.
C1, C2 C1608X5R0J475K TDK
( )1
4.7µF Ceramic Capacitor, 6.3V, X5R, Size 0603 2
R1 CRCW06031003FT1 Vishay ( )2 100kΩ, 1%, Size 0603 1
L1
LQM21PN1 MurataR0MC0D ( )3 1µH, 0.8A, 190mΩ, L2mm × × W1.25mm H0.5mm
1
LQH32CN1R0M33 Murata 1µH, 1A, 60mΩ, L3.2mm × × W2.5mm H2.0mm
LQM31PN1R0M00 Murata 1µH, 1.2A, 120mΩ, L3.2mm × × W1.6mm H0.85mm
LQM31PNR47M00 Murata 0.47µH, 1.4A, 80mΩ, L3.2mm × W1.8mm × H0.85mm
GLF251812T1R0M TDK 1µH, 0.8A, 100mΩ, L2.5mm × × W1.8mm H1.2mm
MIPF2520D1R5 FDK( )4 1.5µH, 1.5A, 70mΩ, L2.5mm × × W2mm H1mm
EPL2010 102- Coilcraft
( )5 1µH, 1A, 86mΩ, L2mm × W1.8mm × H1mm
U1 - MIC23031 xYMT Micrel, Inc.
( )6
4MHz PWM 400mA Buck Regulator with HyperLight Load 1
Notes:
1. TDK: www.tdk.com.
2. Vishay : www.vishay.com.
3. Murata: www.murata.com.
4. FDK: www.fdk.co.jp.
5. Coilcraft: www.coilcraft.com.
6. Micrel, Inc.: www.micrel.com.
June 17, 2014 3 Revision 2.0


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Modell: MIC23031-4YMT

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