High Efficiency 1.5MHz, Step up Regulator

EC9210

Page 13 of 16

5E29N-Rev.F002

Function Description

Main Control Loop

The EC9210 is a constant frequency and current-mode switching

regulator. In normal operation, the internal N channel power

MOSFET is turned on each cycle when the oscillator sets an

internal RS latch, and then turned off when an internal comparator

(ICMP) resets the latch. The peak inductor current at which ICMP

resets the RS latch is controlled by the voltage on the COMP node

which is the output of the error amplifier (EAMP). An external

associated with the 1.23V reference, which in turn, it causes the

COMP voltage to increase until the average inductor current

matches the new load current.

VIN Under-Voltage Lockout (UVLO)

The Under-Voltage Lockout (UVLO) circuit compares the input

voltage at VIN with the UVLO threshold to ensure the input voltage

is high enough for reliable operation. The 100mV (typ) hysteresis

prevents supply transients from causing a restart. Once the input

voltage exceeds the UVLO rising threshold, startup begins. When

the input voltage falls below the UVLO falling threshold, the

controller turns off the converter.

Soft-Start

The EC9210 has a built-in soft-start to control the output voltage

rise during start-up. During soft-start, an internal ramp voltage,

connected to the one of the positive inputs of the error amplifier,

raises up to replace the reference voltage (1.23V typical) until the

ramp voltage reaches the reference voltage.

Current-Limit Protection

The EC9210 monitors the inductor current, flows through the

N-channel MOSFET, and limits the current peak at current-limit

level to prevent loads and the EC9210 from damaging during

overload or short-circuit conditions.

Over-Temperature Protection (OTP)

The over-temperature circuit limits the junction temperature of the

EC9210. When the junction temperature exceeds 150℃, a thermal

sensor turns off the power MOSFET allowing the devices to cool.

The thermal sensor allows the converters to start a soft-start

process and regulates the output voltage again after the junction

temperature cools by 40℃. The OTP is designed with a 40℃

continuous thermal overload conditions increasing the lifetime of

the device.

Enable/Shutdown

Driving EN to the ground places the EC9210 in shutdown mode.

When in shutdown, the internal power MOSFET turns off, all

internal circuitry shuts down, and the quiescent supply current

reduces to 1

μA maximum.