MIC33163 Datasheet, PDF (15/19 Pages) Micrel Semiconductor – Buck Regulator with Integrated Inductor

Micrel, Inc.
Over 100mA, efficiency loss is dominated by MOSFET
R_DSON and inductor losses. Higher input supply voltages
will increase the gate-to-source threshold on the internal
MOSFETs, thereby reducing the internal R_DSON. This
improves efficiency by reducing DC losses in the device.
HyperLight Load (HLL) Mode
MIC33163/4 uses a Micrel-patented minimum on- and
off-time proprietary control loop (PCL) called HyperLight
Load (HLL). When the output voltage falls below the
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. If the output voltage is over the
regulation threshold, then the error comparator turns the
PMOS off for a minimum-off-time until the output drops
below the threshold. The NMOS acts as an ideal rectifier
that conducts when the PMOS is off. Using a NMOS
switch instead of a diode allows for lower voltage drop
across the switching device when it is on. The
asynchronous switching combination between the PMOS
and the NMOS allows the control loop to work in
discontinuous mode for light load operations. In
discontinuous mode, the MIC33163/4 works in pulse
frequency modulation (PFM) to regulate the output. As
the output current increases, the off-time decreases, thus
provides more energy to the output. This switching
scheme improves the efficiency of MIC33163/4 during
light load currents by only switching when it is needed. As
the load current increases, the MIC33163/4 goes into
continuous conduction mode (CCM) and switches at a
frequency centered at 4MHz.
As shown in Figure 3, as the output current increases,
the switching frequency also increases until the
MIC33163/4 goes from HLL mode to PWM mode at
approximately 120mA. The MIC33163/4 will switch at a
relatively constant frequency around 4MHz once the
output current is over 220mA.
MIC33163/4
Emission Characteristic of MIC33163/4
The MIC33163/4 integrates switching components in a
single package for reduced emissions compared to
standard buck regulators with external MOSFETs and
inductors. The radiated EMI scans for the MIC33163/4
are shown in the Functional Characteristic.
The limit on the graph is per EN55022 class B standard.
10000
Switching Frequency
vs. Output Current
1000
V_IN = 5V
100
V_IN = 3.6V
10
1
1
10
100
1000
OUTPUT CURRENT (mA)
Figure 3. SW Frequency vs. Output Current
May 22, 2014
15
Revision 1.1