MP2214 – 16V, 4A, 600kHz SYNCHRONOUS STEP-DOWN CONVERTER
the MP2214 is pre-biased to a certain voltage
FUNCTIONAL DESCRIPTION
during startup, the IC will disable the switching of
both high-side and low-side switches until the
voltage on the internal soft-start capacitor
exceeds the sensed output voltage at the FB pin.
PWM Control
The MP2214 is a constant frequency peak-
current-mode control PWM switching regulator.
Refer to the functional block diagram. The high
side N-Channel DMOS power switch turns on at
the beginning of each clock cycle. The current in
the inductor increases until the PWM current
comparator trips to turn off the high side DMOS
switch. The peak inductor current at which the
current comparator shuts off the high side power
switch is controlled by the COMP voltage at the
output of feedback error amplifier. The
transconductance from the COMP voltage to the
output current is set at 11.25A/V.
Over Current Protection
The MP2214 offers cycle-to-cycle current limiting
for both high-side and low-side switches. The
high-side current limit is relatively constant
regardless of duty cycles. When the output is
shorted to ground, causing the output voltage to
drop below 70% of its nominal output, the IC is
shut down momentarily and begins discharging
the soft start capacitor. It will restart with a full
soft-start when the soft- start capacitor is fully
discharged. This hiccup process is repeated until
the fault is removed.
This current-mode control greatly simplifies the
feedback compensation design by approximating
the switching converter as a single-pole system.
Only Type II compensation network is needed,
Bootstrap (BST PIN)
The gate driver for the high-side N-channel
DMOS power switch is supplied by a bootstrap
capacitor connected between the BS and SW pins.
When the low-side switch is on, the capacitor is
charged through an internal boost diode. When
the high-side switch is on and the low-side switch
turns off, the voltage on the bootstrap capacitor is
boosted above the input voltage and the internal
bootstrap diode prevents the capacitor from
discharging.
which
Compensation in the MP2214 simplifies the
compensation design, minimizes external
component counts.
is
integrated
into
the
MP2214.
Enable and Frequency Synchronization
(EN/SYNC PIN)
This is a dual function input pin. Forcing this pin
below 0.4V for longer than 4us shuts down the
part; forcing this pin above 1.6V for longer than
4µs turns on the part. Applying a 500KHz to 2MHz
clock signal to this pin also synchronizes the
internal oscillator frequency to the external clock.
When the external clock is used, the part turns on
after detecting the first few clocks regardless of
duty cycles. If any ON or OFF period of the clock
is longer than 4µs, the signal will be intercepted
as an enable input and disables the
synchronization.
No external bootstrap diode is required for typical
applications. For applications with low input VCC
voltage or where output voltage is very close to
input voltage, an external Schottky diode may be
connected from the VCC to BS pins to charge the
bootstrapped capacitor more strongly for
increased gate drive voltage. When using the
external bootstrap diode, a resistor at the
regulator output or a minimal load current may be
required as the bootstrapped capacitor always
see the supply voltage even when the part is
disabled.
Soft-Start and Output Pre-Bias Startup
When the soft-start period starts, an internal
current source begins charging an internal soft-
start capacitor. During soft-start, the voltage on
the soft-start capacitor is connected to the non-
inverting input of the error amplifier. The soft-start
period lasts until the voltage on the soft-start
capacitor exceeds the reference voltage of 0.8V.
At this point the reference voltage takes over at
the non-inverting error amplifier input. The soft-
start time is internally set at 120µs. If the output of
Input UVLO
Both VCC and IN pins have input UVLO detection.
Until both VCC and IN voltage exceed under
voltage lockout threshold, the parts remain in
shutdown condition. There are also under voltage
lockout hysesteres at both VCC and IN pins.
MP2214 Rev. 0.9
9/1/2010
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