RT7339P
COMP Sourcing Current
The output short-circuit protection is masked during the
first 48.7ms (typ.) of power on (VDD > V
TH_ON
).
20μA
Output Diode Short-Circuit Protection
When the output diode is damaged as short-circuit, the
transformer will be led to magnetic saturation and the
main switch will suffer from a high current stress. To
2.25V
2.5V
2.75V
G
20 m =
μ
A
/V
avoid the above situation, an output diode short-circuit
protection is built-in. When CS voltage V
CS
exceeds
the threshold (V
CS_SD
0.85V typ.) of the output diode
short-circuit protection, the RT7339P will shut down the
PWM output (GATE pin) in few cycles to prevent the
converter from damage. It will be auto-restarted when
the fault condition is recovered.
-20μA
Figure 5. Non-linear Gm
Standby Mode
When COMP is lower than 0.3V for 27.3ms (typ.), the
DMAG reference voltage (V
DMAG_REF
, 2.5V typ.) will
be reduced to the reference voltage in standby mode
(V
REF_SB
, 1.2V typ.). Therefore, the extreme low power
consumption can be achieved.
Protections
The RT7339P integrates comprehensive protection
functions, including output over voltage protection,
output short-circuit protection, output diode short-circuit
protection, VDD under-voltage lockout (UVLO), VDD
over-voltage protection (VDD OVP), input under / over
voltage protection, external / internal over-temperature
protection (OTP), and cycle-by-cycle high/low line
current limitation.
VDD pin will sink an extra current (500A typ.) when
protections are triggered except for VDD UVLO and
cycle-by-cycle high/low line current limitation.
Output Short-Circuit Protection
The
RT7339P
implements
output
short-circuit
VDD Under-Voltage Lockout (UVLO) and
Over-Voltage Protection (VDD OVP)
The RT7339P will be enabled when VDD voltage (V
DD
)
exceeds rising UVLO threshold (V
TH_ON
, 21.5V typ.)
and disabled when V
DD
is lower than falling UVLO
threshold (V
TH_OFF
, 7.3V typ.).
When
V
DD
exceeds
its
over-voltage
threshold
(V
DD_OVP
, 37V typ.), the PWM output of the RT7339P
is shut down. It will be auto-restarted when the VDD is
recovered to a normal level.
It should be noticed that if the startup circuit without the
depletion MOSFET, the startup resistor R
HV
is
suggested to be greater than 500k. Otherwise VDD
may trigger VDD OVP in standby mode or no load
condition.
Input Over-Voltage and Under-Voltage Protection
When I
DMAG
is over the threshold current of V
IN
over-voltage protection (I
DMAG_OCP
) in few cycles, the
GATE will shut down to avoid over stress on
components. As soon as the input voltage drops below
the brown-out threshold for 97.8ms (typ.), the controller
will shut down until it recovers to the brown-in
threshold.
Internal and External Over-Temperature Protection
(OTP)
The RT7339P provides the internal OTP function to
protect the controller itself from suffering the thermal
stress and permanent damage. Once the junction
protection by DMAG and CS pins. Once the DMAG
voltage is lower than 0.5V and the current sense
voltage V
CS
exceeds the peak current limitation for few
cycles, the converter will be shut down to prevent
damage. It will be auto-restarted when the output is
recovered.
Copyright © 2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS7339P-03
August 2019
www.richtek.com
5
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
