The JTMA7336 monitors the output current, flowing through th

一,产品概述(General Description)
Main Control Loop
The JTMA7336 is a constant frequency current mode switching regulator.
During normal operation, the internal 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 0.8V reference,
which in turn causes the COMP voltage to increase until the average inductor
current matches the new load current.
VIN Power-On-Reset (POR) and EN Under-voltageLockout
The JTMA7336 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 4.05V (typical)
with 0.3V 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 JTMA7336
When the junction temperature exceeds TJ =+160oC, a thermal sensor turns
off the power MOSFET, allowing the device to cool down. The thermal sensor
allows the converter to start a start-up process and regulate the output voltage
again after the junction temperature cools by 50oC.The OTP designed with a 50 oC
hysteresis lowers the average T J during c ontinuous thermal overload conditions,
increasing life time of the IC.
Enable/Shutdown
Driving EN to ground places the JTMA7336 in shutdown.When in shutdown, the
internal N-Channel power MOSFET turns off, all internal circuitry shuts down and
the quiescent supply current reduces to 0.3µA.

Current-Limit Protection
The JTMA7336 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
frequency allows the inductor current to safely discharge,thereby preventing current
runaway. The oscillator’s frequency 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 high-and low-side MOSFET gate driver off. As soon as the output
voltage is within regulation, the OVP comparator is disengaged. The chip will restore its
normal operation.
二.产品特点(Features)
Wide Input Voltage from 4.5V to 24V
2A Continuous Output Current
Adjustable Output Voltage from 0.8V to 20V
Intergrated High/Low Side MOSFET
PFM/PWM mode Operation
Fixed 340kHz Switching Frequency
Stable with Low ESR Ceramic Output Capacitors
Power-On-Reset Detection
Programmable Soft-Start
Over-Temperature Protection
Current-Limit Protection with Frequency Foldback
Enable/Shutdown Function
Small TDFN3x3-10 Packages
Lead Free and Green Devices Available (RoHS Compliant)

三,应用范围 (Applications)

LCD Monitor/TV

Set-Top Box
DSL, Switch HUB
Notebook Computer

四.下载产品资料PDF文档

jtma7336

JTMA7337

五,产品封装图 (Package)

六.电路原理图

(责任编辑：oumao18)