MIC23150 Evaluation Board
4MHz 2A Buck Regulator with
HyperLight Load
Getting Started
General Description
1. Connect an external supply to the V (J1)
IN
The MIC23150 is a 2A 4MHz switching regulator featuring
terminal. Apply the desired input voltage to V
IN
HyperLight Load mode. The MIC23150 is highly efficient
(J1) and ground (J2) terminals of the evaluation
throughout the entire output current range, drawing just
board, paying careful attention to polarity and
23A of quiescent current in operation. The tiny 2mm x
supply voltage (2.7V V 5.5V). An ammeter
IN
2mm MLF package, in combination with the 4MHz
may be placed between the input supply and the
switching frequency, enables a compact sub-1mm height
V (J1) terminal. Be sure to monitor the supply
IN
solution with only three external components. The
voltage at the V (J1) terminal, since the ammeter
IN
MIC23150 provides accurate output voltage regulation
and/or power lead resistance can reduce the
under the most demanding conditions and responds
voltage supplied to the device.
extremely quickly to a load transient with exceptionally
small output voltage ripple.
2. Connect a load to the V (J3) and ground
OUT
Factoring in the output current, the internal circuitry of the terminal (J4). The load can be either passive
MIC23150 automatically selects between two modes of
(resistive) or active (electronic load). An ammeter
operation for optimum efficiency. Under light load may be placed between the load and the output
conditions, the MIC23150 goes into HyperLight Load
terminal. Ensure the output voltage is monitored at
mode. HyperLight Load uses a Pulse-Frequency the V (J3) terminal.
OUT
Modulation (PFM) control scheme that controls the off time
3. Enable the MIC23150. The MIC23150 evaluation
at light load. This proprietary architecture reduces the
board has a pull-up resistor to V . To disable the
amount of switching needed at light load, thereby IN
device, apply a voltage below 0.5V to the EN (J5)
increasing operating efficiency. The MIC23150 attains up
terminal. In the absence of the pull-up resistor, the
to 87% efficiency at 1mA output load. As the load current
device is enabled by applying a voltage greater
increases beyond approximately 100mA, the device
than 1.2V to the EN (J5) terminal. The enable pin
operates using the Pulse-Width Modulation (PWM) method
must be either pulled high or low for proper
for up to 93% efficiency at higher load. The two modes of
operation. Removing the pull-up resistor and
operation ensure the highest efficiency across the entire
leaving the pin floating will cause the regulator to
load range.
operate in an unknown state.
The MIC23150 operates from an input voltage range of
2.7V to 5.5V and features internal power MOSFETs that
Output Voltage
deliver up to 2A of output current. This step-down regulator
The MIC23150 evaluation board is available with the
provides an output voltage accuracy of +/-2.5% across the
following output voltage options listed below:
junction temperature range of -40C to +125C. The
MIC23150 is available in fixed output versions supporting
an output voltage as low as 1.0V.
Ordering Information
(2)
Requirements
Part Number Description
(1)
The MIC23150 evaluation board requires an input power
MIC23150-CYMT EV 1.0V Fixed Output Evaluation Board
source that is able to deliver greater than 2A at 2.7V to the
(1)
MIC23150-4YMT EV 1.2V Fixed Output Evaluation Board
MIC23150. The output load can either be an active
MIC23150-GYMT EV 1.8V Fixed Output Evaluation Board
(electronic) or passive (resistive) load.
MIC23150-SYMT EV 3.3V Fixed Output Evaluation Board
Note:
1. Contact Micrel Marketing
2. Other voltage options available on request. Contact Micrel.
HyperLight Load is a trademark of Micrel, Inc. MLF is a registered trademark of Amkor Technology.
Micrel Inc. 2180 Fortune Drive San Jose, CA 95131 USA tel +1 (408) 944-0800 fax + 1 (408) 474-1000 Micrel, Inc. MIC23150 Evaluation Board
As shown in the previous equation, the load at which
HyperLight Load Mode
MIC23150 transitions from HyperLight Load mode to
MIC23150 uses a minimum on and off time proprietary
PWM mode is a function of the input voltage (V ), output
IN
control loop (patented by Micrel). When the output voltage
voltage (V ), duty cycle (D), inductance (L) and
OUT
falls below the regulation threshold, the error comparator
frequency (f). As shown in Figure 1, as the Output Current
begins a switching cycle that turns the PMOS on and
increases, the switching frequency also increases until the
TM
keeps it on for the duration of the minimum-on-time. This
MIC23150 goes from HyperLight Load mode to PWM
increases the output voltage. If the output voltage is over
mode at approximately 120mA. The MIC23150 will switch
the regulation threshold, then the error comparator turns
at a relatively constant frequency around 4MHz once the
the PMOS off for a minimum-off-time until the output drops
output current is over 120mA.
below the threshold. The NMOS acts as an ideal rectifier
that conducts when the PMOS is off. Using a NMOS
SW Frequency
switch instead of a diode allows for lower voltage drop
vs Output Current
across the switching device when it is on. The
10
asynchronous switching combination between the PMOS
V = 3.0V
and the NMOS allows the control loop to work in
IN
V = 3.6V
1 IN
discontinuous mode for light load operations. In
discontinuous mode, the MIC23150 works in pulse
V = 4.2V
IN
frequency modulation (PFM) to regulate the output. As the
0.1
output current increases, the off-time decreases, thus
provides more energy to the output. This switching
L = 4.7H
0.01
scheme improves the efficiency of MIC23150 during light
V = 1.8V
OUT
load currents by only switching when it is needed. As the
C = 4.7F
OUT
0.001
load current increases, the MIC23150 goes into
1 10 100 1000 10000
continuous conduction mode (CCM) and switches at a
OUTPUT CURRENT (mA)
frequency centered at 4MHz. The equation to calculate the
load when the MIC23150 goes into continuous conduction
mode may be approximated by the following formula:
Figure 1. SW Frequency vs. Output Current
(V -V )D
IN OUT
I >
LOAD
2Lf
M9999-081709-A
August 2009 2
SW FREQUENCY (MHz)