MIC23201 Datasheet, PDF (11/20 Pages) Micrel Semiconductor – 2MHz PWM 2A Buck Regulator

Micrel Inc.
Functional Diagram
MIC23201
Figure 1. Simplified MIC23201 Functional Block Diagram
Functional Description
VIN
The input supply (VIN) provides power to the internal
MOSFETs for the switch mode regulator along with the
internal control circuitry. The VIN operating range is 2.7V
to 5.5V so an input capacitor, with a minimum voltage
rating of 6.3V, is recommended. Due to the high
switching speed, 22µF bypass capacitor placed close to
VIN and the power ground (PGND) pin is required. Refer
to the layout recommendations for details.
SVIN
The input supply (SVIN) provides power to internal
control circuitry. This pin is connected externally to the
VIN pin. A 2.2µF ceramic capacitor from the SVIN pin to
AGND must be placed next to the IC.
EN
A logic high signal on the enable pin activates the output
voltage of the device. A logic low signal on the enable
pin deactivates the output and reduces supply current to
0.01µA. MIC23201 features built-in soft-start circuitry
that reduces in-rush current and prevents the output
voltage from overshooting at start up. Do not leave this
pin floating.
SW
The switch (SW) connects directly to one end of the
inductor and provides the current path during switching
cycles. The other end of the inductor is connected to the
load, SNS pin and output capacitor. Due to the high
speed switching on this pin, the switch node should be
routed away from sensitive nodes whenever possible.
SS
The soft start (SS) pin is used to control the output
voltage ramp up time. The approximate equation for the
ramp time in seconds is 270x10³ x ln(10) x C_SS. For
example, for a C_SS = 470pF, T_rise ~ 300µs. See the
Typical Characteristics curve for a graphical guide. The
minimum recommended value for C_SS is 100pF.
SNS
The sense (SNS) pin is connected to the output of the
device to provide feedback to the control circuitry. The
August 2012
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M9999-082912-A