SC2615 Semtech, SC2615 Datasheet - Page 8

• Manufacturer Part Number: SC2615
• Description: Complete DDR Power Solution
• Manufacturer: Semtech

desirable.
A MOSFET in series with the top pass MOSFET (See typical
application circuit) must block this reverse current during
S3. This MOSFET can be driven from the inverted BF_CUT
signal. By removing the gate drive for this series MOSFET,
the current path from the VDDQ supply back into the
input power source is removed. This MOSFET is enhanced
during S0 state.
Short Circuit Protection
Short Circuit Protection is implemented by sensing the
VDDQ voltage. If the SS/EN pin has risen above 1.25V
(i.e. the controller has completed the startup cycle), and
the output falls to 60% of its nominal voltage, as sensed
by the FB pin, the TG pin is latched off and the linear
controllers shut down. To recover from this condition,
either the power rails have to be recycled, or the SS/EN
pin must be pulled low and released to restart controller
operation. The short circuit protection function is disabled
when any of the input rails are below their respective
UVLO thresholds.
Thermal Shutdown
There are three independent Thermal Shutdown
protection circuits in the SC2615, the VDDQ linear
regulator the VTT source regulator, and the VTT sink
regulator. If any of the three regulators’ temperature
rises above the threshold, that regulator will turn off
independently, until the temperature falls below the
thermal shutdown limit.
Power Good
An open collector output provides indication that the
VDDQ is regulating. This is accomplished by monitoring
the SS/EN pin. When the voltage on this pin has risen
above 1.0V, the PGOOD goes high (open). When BF_CUT
goes high (standby), the 5V and 12V rails go low, and the
SS/EN also goes low. Subsequently, PWRGD will also go
low, and stays low until the 3.3V and/or 12V rails are
recycled and rise above their respective UVLO thresh-
olds.
POWER MANAGEMENT
Applications Information (Cont.)
2003 Semtech Corp.
8
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SC2615