MIC23158 Datasheet, PDF (16/20 Pages) Micrel Semiconductor – 3MHz PWM Dual 2A Buck Regulator with HyperLight Load and Power Good

Micrel Inc.
As the load current increases, the MIC23158/9 goes into
continuous conduction mode (CCM) and switches at a
frequency centered at 3MHz. The equation to calculate
the load when the MIC23158/9 goes into continuous
conduction mode may be approximated by the following
formula:
I_LOAD
>
 ^(VIN

− V_OUT
2L × f
)
×
D

Eq. 7
As shown in Equation 7, the load at which the
MIC23158/9 transitions from HyperLight Load mode to
PWM mode is a function of the input voltage (V_IN), output
voltage (V_OUT), duty cycle (D), inductance (L) and
frequency (f). As shown in Figure 5, as the output
current increases, the switching frequency also
increases until the MIC23158/9 goes from HyperLight
Load mode to PWM mode at approximately 180mA. The
MIC23158/9 will switch at a relatively constant frequency
around 3MHz once the output current is over 180mA.
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0.1
Switching Frequency
vs. Output Current
L=1.0µH
L=0.47µH
1
10
100
1000
OUTPUT CURRENT (mA)
10000
Figure 5. SW Frequency vs. Output Current
MIC23158/9
November 2012
16
M9999-110812-A