MP3212 MPS, MP3212 Datasheet - Page 8

• Manufacturer Part Number: MP3212
• Description: 1.3a, 1mhz Step-up Regulator With Integrated Input Disconnect Switch
• Manufacturer: MPS

OPERATION
The MP3212 uses a constant frequency, peak
current mode boost regulation architecture to
regulate the feedback voltage. The operation of
the MP3212 can be understood by referring to
the block diagram of Figure 1.
At the beginning of each cycle, the power
MOSFET-M1 turns on, to prevent sub-harmonic
oscillations at duty cycles greater than 50%, a
stabilizing ramp is added to the output of the
current sense amplifier. When the output voltage
of current sense amplifier equals to the output
voltage of error amplifier, the power MOSFET-M1
turns off.
The voltage at the output of the error amplifier is
an amplified version of the difference between
the 1.23V reference voltage and the feedback
voltage.
corresponded to the error amplifier output. If the
feedback voltage starts to drop, the output of
error amplifier increases, which results in more
current flowing through the power MOSFET-M1
and thus increases the power delivered to the
output. The use of current mode control improves
transient response.
To prevent the battery from discharging, when
MP3212 is disabled, the inductor is automatically
disconnected from the input supply.
Fault Control
MP3212 Rev. 0.9
3/21/2008
Overcurrent drawn from VDDOUT
Over Temperature on chip
FAULT DESCRIPTION
Overvoltage at VOUT
Undervoltage at VDD
The
MP3212–1.3A, 1MHz, STEP-UP REGULATOR WITH INTEGRATED INPUT DISCONNECT SWITHCH
peak
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inductor
current
© 2011 MPS. All Rights Reserved.
FAULT CONDITION
V(VDD) < V
I(VDDOUT) > I
V(VOUT) > V
www.MonolithicPower.com
Tj > T
is
SHDN_TH
UVLO,LO
The MP3212 has internal soft start control and
internal loop compensation to save external
components.
The MP3212 monitors input under voltage
conditions, output over voltage conditions, and
over temperature events for input under voltage
lockout, output over voltage protection and over
temperature protection.
Start-Up Sequence
After SHDN pin is pulled low, or a restart is
triggered by the fault condition, MP3212 will go
through a start up sequence described as below.
At the beginning of start up, the VDDOUT switch
is configured as the current source to regulate
the inrush current, and pre-charge the capacitor
at Vout. There is 2ms timer to make sure the
capacitor at Vout is charged up close to Vin
minus a diode drop. However, if Vout is still not
charged up after timeout, MP3212 will stay in this
mode.
After 2ms timeout, if Vout is charged up close to
Vin minus a diode drop, then the VDDOUT
switch will be fully turned on and connect the
inductor to VDD. MP3212 will enter soft start.
The error amplifier voltage is increased slowly
during soft start to prevent overshoot. When VFB
approaches the internal bandgap voltage, the
MP3212 starts normal operation.
OV
OI
FAULT REACTION
Disables I/Os and waits until V(VDD)
reaches V
start-up sequence
Disables VDDOUT switch and SW switch
and immediately restarts the start-up
sequence
Disables VDDOUT switch and SW switch
and waits until output voltage V(VOUT)
drops to V
up sequence
Disables VDDOUT switch and SW switch
and waits until junction temp drops to
T
sequence
SHDN_TH-
T
SHDN_HYS
OV
UVLO,HI
- V
OV_Hys
on to begin with the
to restart the start-up
to restart the start-
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