RT8203GA Richtek USA Inc, RT8203GA Datasheet - Page 19

• Manufacturer Part Number: RT8203GA
• Description: IC CTRLR SMPS STPDN DUAL 28SSOP
• Manufacturer: Richtek USA Inc

Specifications of RT8203GA

• Output Isolation: Isolated
• Frequency Range: Adjustable, Selectable
• Voltage - Input: 7 V ~ 24 V
• Voltage - Output: Selectable
• Power (watts): 1.05W
• Operating Temperature: -10°C ~ 85°C
• Package / Case: 28-SSOP (0.150", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Soft-Start
A build-in soft-start is used to prevent surge current from
power supply input after ONx is enabled. It clamps the
ramping of internal reference voltage which is compared
with the FBx signal. The
period. Furthermore, the maximum allowed current limit
is segmented in 3 steps : 20%, 50%, and 100% during
the 1.5ms period. The current limit steps can minimize
the V
is determining fixed or adjustable output.
POR and UVLO
Power On Reset (POR) occurs when V
approximately 3.5V, resetting the fault latch and preparing
the PWM for operation. Below 4.25V(min), the VCC
undervoltage lockout (UVLO) circuitry inhibits switching
by keeping UGATEx and LGATEx low.
Power Good Output (PGOOD)
The PGOOD is an open-drain type output. PGOOD is
actively held low in soft-start, standby, and shutdown. It is
released when both outputs voltage above than 91.25% of
nominal regulation point. The PGOOD goes low if either
output turns of or is 8.75% below its
point.
Output Over Voltage Protection (OVP)
The output voltage can be continuously monitored for over
voltage. When over voltage protection is enabled, if the
output exceeds the over voltage threshold, over voltage
fault protection is triggered and the LGATEx low side gate
drivers are forced high. This activates the low side MOSFET
switch, which rapidly discharges the output capacitor and
reduces the input voltage.
Note that LGATEx latching high causes the output voltage
to dip slightly negative when energy has been previously
stored in the LC tank circuit. For loads that cannot tolerate
a negative voltage, place a power Schottky diode across
the output to act as a reverse polarity clamp. Connect PRO
to
which is 11% above the
If the over voltage condition is caused by a short in high
side switch, turning the low side MOSFET on 100% creates
an electrical short between the battery and GND, blowing
the fuse and disconnecting the battery from the output.
DS8203-04 March 2011
GND to enable the default over voltage threshold level,
OUT
folded-back in the soft-start duration when RT8203
typical soft-start duration is 1.5ms
set voltage.
nominal regulation
IN
rises above
Output Under Voltage Protection (UVP)
The output voltage can be continuously monitored for under
voltage. When under voltage protection is enabled ( PRO
= GND), if the output is less than 70% of the error-amplifier
trip voltage, under voltage protection is triggered, then both
UGATEx and LGATEx gate drivers are forced low. In order
to remove the residual charge on the output capacitor during
the UV period, if PHASEx is greater than 1V, the LGATEx
gate driver is forced high until PHASEx lower than 1V.
Connect UVP to GND to disable under voltage protection.
Thermal Protection
The RT8203 have thermal shutdown to prevent the overheat
damage. Thermal shutdown occurs when the die
temperature exceeds 150°C. All internal circuitry shuts
down during thermal shutdown. The RT8203 will trigger
thermal shutdown if LDOx is not supplied from VOUTx,
while input voltage on VIN and drawing current form LDOx
are too high. Even if LDOx is supplied from VOUTx,
overloading the LDOx causes large power dissipation on
automatic switches, which may result in thermal shutdown.
Discharge Mode
When PRO is low and a transition to standby or shutdown
mode occurs, or the output under voltage fault latch is
set, the outputs discharge mode is triggered. During
discharge mode, there are two paths to discharge the
outputs capacitor residual charge during discharge mode.
The first is output capacitor discharge to GND through an
internal 17Ω switch. The second is output capacitor
discharged by forcing the low-side MOSFET turn on/off
until PHASEx voltage decrease under 1V.
Shutdown Mode
Drive EN below the precise EN input falling-edge trip level
to place the RT8203 in their low-power shutdown state.
When shutdown mode activates, the reference turns off,
making the threshold to exit shutdown inaccurate. For
automatic shutdown and startup, connect EN to VIN. If
PRO is low, both SMPS outputs will enter discharge mode
before entering true shutdown. The
edge threshold on EN can be used to detect a specific
analog voltage level and shutdown the device. Once in
shutdown, the 1.6V rising-edge threshold activates,
providing sufficient hysteresis for most application.
accurate 1V falling-
RT8203
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