MCP1612-300I/MS Microchip Technology, MCP1612-300I/MS Datasheet - Page 10

• Manufacturer Part Number: MCP1612-300I/MS
• Description: Switching Converters, Regulators & Controllers 1.4MHz 1A Synch-Buck
• Manufacturer: Microchip Technology

Specifications of MCP1612-300I/MS

• Output Current: 1.0 A
• Mounting Style: SMD/SMT
• Package / Case: MSOP-8
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

MCP1612
4.0
4.1
The MCP1612 is a 1A Synchronous Buck converter
switching at 1.4 MHz to minimize external component
size and cost. While utilizing a fixed-frequency current
mode architecture, the MCP1612 provides fast
response to sudden load changes and overcurrent
protection in the event of a shorted load. The input
voltage range is 2.7V to 5.5V, while the output voltage
is adjustable by properly setting an external resistor
divider and can range from 0.8V to V
start, Undervoltage Lockout (UVLO) and overtempera-
ture
component count.
4.2
The MCP1612 incorporates a peak current mode
control scheme. Peak Current mode is used to obtain
high gain in the PWM control loop for very fast
response to dynamic line and load conditions. With
both the P-Channel and the N-Channel MOSFETs
turned off, the beginning of a cycle occurs on the
negative edge of the internal 1.4 MHz oscillator, the
P-Channel MOSFET turns on and current ramps up
into the Buck inductor. The inductor current is sensed
and tied to one input of a high-speed comparator. The
other input of the high-speed comparator is the error
amplifier output. This is the amplified difference
between the internal 0.8V reference and the divided
down V
MCP1612. When the sensed inductor current ramps up
to the point that it is equal to the amplified error signal,
the high-speed comparator output switches states and
the P-Channel MOSFET is turned off until the begin-
ning of the next clock cycle and the N-Channel is
turned on. The width of the pulse or “duty cycle” is
ideally determined by the V
converter. The actual duty cycle is slightly larger to
account for the non-ideal losses of the integrated
MOSFET switches and the losses in the external
inductor.
4.3
The MCP1612 is capable of operating over a wide
range of input voltages. The PWM architecture allows
for the P-Channel MOSFET to achieve 100% duty
cycle operation for applications that have minimal input
voltage headroom. During 100% Duty Cycle mode, the
output voltage (V
Resistance (P-Channel R
DS21921A-page 10
protection
OUT
DETAILED DESCRIPTION
Device Overview
Current Mode Control Scheme
Low Dropout Operation
signal at the Feedback pin of the
minimize
OUT
) = Output Current (I
DSON
OUT
external
/V
+ R
IN
INDUCTOR
ratio of the DC/DC
IN
. Integrated soft
circuitry
).
OUT
and
) x
4.4
Cycle-by-cycle current limit is used to protect the
MCP1612 from being damaged when an external short
circuit is applied. The typical peak current limit is 2.3A.
If the sensed inductor current reaches the 2.3A limit,
the P-Channel MOSFET is turned off, even if the output
voltage is not in regulation.
4.5
During normal power-up as V
protection setting or, in the case of a logic-low to logic-
high transition on the shutdown pin, the rise time of the
MCP1612 output voltage is controlled by the soft start
feature. This is accomplished by slowly allowing the
output of the error amplifier to rise. This feature pre-
vents the output voltage from overshooting the desired
value and the sudden inrush of current, depleting the
input capacitors and causing a large dip in input
voltage. This large dip in the input voltage could trip the
UVLO threshold, causing the converter to shutdown
prior to reaching steady-state operation.
4.6
The UVLO feature uses a comparator to sense the
input voltage level (V
than the voltage necessary to properly operate the
MCP1612, the UVLO feature will hold the converter off.
When V
UVLO is released and soft start begins. For the
MCP1612, the UVLO protection threshold is a maxi-
mum of 2.7V. Hysteresis is built into the UVLO circuit to
compensate for input impedance. For example, once
the converter starts, if there is any resistance between
the input voltage source and the converter, there will be
a voltage drop at the converter input equal to I
The typical hysteresis for the MCP1612 is 200 mV.
4.7
The MCP1612 has an integrated overtemperature pro-
tection circuit that monitors the device junction temper-
ature and shuts the device off if the junction
temperature exceeds the typical 160°C threshold. If the
overtemperature threshold is reached, the soft start is
reset so that when the junction temperature cools to
approximately 151°C, the device will automatically
restart and the output voltage will not overshoot.
4.8
The SHDN pin is used to turn the MCP1612 on and off.
When the SHDN pin is tied low, the MCP1612 is off.
When tied high, the MCP1612 will be enabled and
begin operation as long as the input voltage is not
below the UVLO threshold.
IN
Current Limit
Soft Start
Undervoltage Lockout (UVLO)
Overtemperature Protection
Shutdown Input Operation
rises above the necessary input voltage, the
IN
). If the input voltage is lower
 2004 Microchip Technology Inc.
IN
rises above the UVLO
IN
x R
IN
.