Main Control Loop
The JTMA7302 is a constant frequency current mode switching regulator. During normal operation, the inter-
nal N-channel power MOSFET is turned on each cycle when the oscillator sets an internal RS latch and would
be turned off when an internal current comparator (ICMP) resets the latch. The peak inductor current at which ICMP
resets the RS latch is controlled by the voltage on the COMP pin, which is the output of the error amplifier
(EAMP). An external resistive divider connected between VOUT and ground allows the EAMP to receive an output
feedback voltage VFB at FB pin. When the load current increases, it causes a slight decrease in VFB relative to
the 0.92V reference, which in turn causes the COMP volt- age to increase until the average inductor current matches
the new load current.
 
VIN Power-On-Reset (POR) and EN Under-voltage Lockout
The JTMA7302 keep monitoring the voltage on VIN pin to prevent wrong logic operations which may occur when
VIN voltage is not high enough for the internal control circuitry to operate. The VIN POR has a rising threshold
of 4.1V (typical) with 0.5V of hysteresis.An external under-voltage lockout (UVLO) is sensed at the EN pin. The
EN UVLO has a rising threshold of 2.5V with 0.2V of hysteresis. The EN pin should be connected
a resistor divider from VIN to EN.After the VIN and EN voltages exceed their respective voltage thresholds,
the IC starts a start-up process and then ramps up the output voltage to the setting of output voltage.
Over-Temperature Protection (OTP)
The over-temperature circuit limits the junction tempera-ture of the JTMA7302. When the junction temperature ex-
ceeds TJ = +160oC, a thermal sensor turns off the power MOSFET, allowing the devices to cool. The thermal sen-
sor allows the converter to start a start-up process and regulate the output voltage again after the junction tem-
perature cools by 50oC.

The OTP is designed with a 50oC hysteresis to lower the average TJ during continuous thermal overload conditions,
increasing lifetime of the lC.
Enable / Shutdown
 
Driving EN to ground places the JTMA7302 in shutdown. When in shutdown, the internal power MOSFET turns off,
all internal circuitry shuts down.
 
Current-Limit Protection
The JTMA7302 monitors the output current, flowing through the N-Channel power MOSFET, and limits the
IC from damages during overload, short-circuit and over- voltage conditions.
 
 
Frequency Foldback
The foldback frequency is controlled by the FB voltage.When the FB pin voltage is under 0.6V, the frequency of
the oscillator will be reduced to 110kHz. This lower fre-quency allows the inductor current to safely discharge,
thereby preventing current runaway. The oscillator’s fre-quency will switch to its designed rate when the feedback
voltage on FB rises above the rising frequency foldback threshold (0.6V, typical) again.
 
 
Over-Voltage Protection
The over-voltage function monitors the output voltage by FB pin. When the FB voltage increase over 120% of the
reference voltage, the over-voltage protection compara-tor will force the low-side MOSFET gate driver high. This
action actively pulls down the output voltage. As soon as the output voltage is within regulation, the OVP compara-
tor is disengaged. The chip will restore its normal operation.