MIC33050-SYHL TR Micrel Inc, MIC33050-SYHL TR Datasheet - Page 2

• Manufacturer Part Number: MIC33050-SYHL TR
• Description: High Efficiency 600mA Inductor-less Buck Regulator Featuring Hyper Light Load
• Manufacturer: Micrel Inc
• Type: Step-Down (Buck)r

Specifications of MIC33050-SYHL TR

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Current - Output: 600mA
• Frequency - Switching: 4MHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 12-MLF®, QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-3353-2

HyperLight Load™ Mode
MIC33050 uses a minimum on and off time proprietary
control loop (patented by Micrel). 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 MIC33050 works
in pulse frequency modulation (PFM) to regulate the
Micrel, Inc.
July 2009
2
output. As the output current increases, the off-time
decreases, thus provides more energy to the output.
This switching scheme improves the efficiency of
MIC33050 during light load currents by only switching
when it is needed. As the load current increases, the
MIC33050 goes into continuous conduction mode (CCM)
and switches at a frequency centered at 4MHz. The
equation to calculate the load when the MIC33050 goes
into continuous conduction mode may be approximated
by the following formula:
As shown in the previous equation, the load at which
MIC33050 transitions from HyperLight Load™ mode to
PWM mode is a function of the input voltage (V
voltage (V
frequency (f).
I
LOAD
OUT
), duty cycle (D), inductance (L) and
>
⎛
⎜ ⎜
⎝
(
V
IN
−
2
V
L
OUT
×
f
MIC33050 Evaluation Board
)
×
D
⎞
⎟ ⎟
⎠
M9999-070709-D
IN
), output