Datasheet

 2014-2016 Microchip Technology Inc. DS20005308C-page 13
MCP16331
FIGURE 4-1: MCP16331 Block Diagram.
4.2 Functional Description
4.2.1 STEP-DOWN OR BUCK CONVERTER
The MCP16331 is a non-synchronous, step-down or buck
converter capable of stepping input voltages, ranging
from 4.4V to 50V, down to 2.0V to 24V for V
IN
> V
OUT
.
The integrated high-side switch is used to chop or
modulate the input voltage using a controlled duty cycle
for output voltage regulation. High efficiency is
achieved by using a low-resistance switch, low forward
drop diode, low Equivalent Series Resistance (ESR),
inductor and capacitor. When the switch is turned on, a
DC voltage is applied across the inductor (V
IN
– V
OUT
),
resulting in a positive linear ramp of inductor current.
When the switch turns off, the applied inductor voltage
is equal to -V
OUT
, resulting in a negative linear ramp of
inductor current (ignoring the forward drop of the
Schottky diode).
For steady-state, continuous inductor current opera-
tion, the positive inductor current ramp must equal the
negative current ramp in magnitude. While operating in
steady state, the switch duty cycle must be equal to the
relationship of V
OUT
/V
IN
for constant output voltage
regulation, under the condition that the inductor current
is continuous or never reaches zero. For discontinuous
inductor current operation, the steady-state duty cycle
will be less than V
OUT
/V
IN
to maintain voltage regula-
tion. The average of the chopped input voltage or SW
node voltage is equal to the output voltage, while the
average of the inductor current is equal to the output
current.
Schottky
Diode
C
OUT
C
BOOST
Slope
Comp
PWM
Latch
+
–
Overtemp
Precharge
R
Comp
Amp
+
–
C
COMP
R
COMP
HS
Drive
CS
V
REG
BG
REF
SS
V
REF
Overtemperature
Boost
Precharge
Charge
500 kHz Osc
S
V
OUT
V
OUT
R
SENSE
GND
Boost
V
IN
EN
R
TOP
R
BOT
BOOST
SW
GND
FB
V
REF
SHDN All Blocks
+
–
C
IN
+
+
Note: EN has an internal pull-up, so the device will start even if the EN pin is left floating.
Diode