RT4723P
Over Current Protection
The RT4723P includes a cycle-by-cycle current limit
function which monitors the inductor current during
each ON period. The power switch will be forced off to
avoid large current damage once the current is over the
limit level.
IL
Input Current
Inductor Current
Short Circuit Protection
Output Current
Time
The RT4723P has an advanced output short-circuit
protection mechanism which prevents the IC from
damage by unexpected applications. When the output
becomes shorted to ground, and the output voltage is
under the limit level with 1ms (typ.) duration, the bias
function enters shutdown mode and can only re-start
normal operation after triggering the SWIRE pin.
DTs
Output Ripple (ac)
Time
VOUT1
Figure 1. Output Ripple Voltage Without Contribution of
ESR
Over Temperature Protection
The RT4723P equips an over temperature protection
circuitry to prevent overheating due to excessive power
dissipation. The OTP will shut down the bias operation
when ambient temperature exceeds 140C. Once the
ambient temperature cools down by approximately
15C, IC will automatically resume normal operation.
To maintain continuous operation, the maximum
junction temperature should be prevented from rising
above 125C.
Under Voltage Lockout
To prevent abnormal operation of the IC in low voltage
condition, an under voltage lockout is included which
shuts down IC operation when input voltage is lower
than the specified threshold voltage.
Soft-Start
The RT4723P employs an internal soft-start feature to
avoid high inrush current during start-up. The soft-start
function is achieved by clamping the output voltage of
the internal error amplifier with another voltage source
that is increased slowly from zero to near VIN during
the soft-start period.
Thermal Considerations
The junction temperature should never exceed the
absolute maximum junction temperature TJ(MAX), listed
under Absolute Maximum Ratings, to avoid permanent
damage to the device. The maximum allowable power
dissipation depends on the thermal resistance of the IC
package, the PCB layout, the rate of surrounding
airflow, and the difference between the junction and
ambient temperatures. The maximum power
dissipation can be calculated using the following
formula :
Negative Output Voltage Setting
The Negative output voltage can be programmed by a
MCU through the dedicated pin according to Table 2
“VON Output Voltage with SWIRE Pulse”.
Shutdown Delay and Discharge
PD(MAX) = (TJ(MAX) TA) / JA
When the SWIRE signal is logic low for more than
350s, the IC function will be shut down. The output
VOP/VON can be actively discharged to GND with
discharge function enabled referring to Table 3
“VOP/VON Shutdown Discharge Selection with SWIRE
Pulse”. In shutdown mode, the input supply current for
the IC is less than 1A.
where TJ(MAX) is the maximum junction temperature,
TA is the ambient temperature, and JA is the
junction-to-ambient thermal resistance.
For continuous operation, the maximum operating
junction temperature indicated under Recommended
Operating Conditions is 125C. The junction-to-
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DS4723P-00 December 2016
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
