EP5358XUI Datasheet, PDF (10/16 Pages) Altera Corporation – 600mA PowerSoC Synchronous Buck Regulator with Integrated Inductor

Excess bulk capacitance on the output of the
device can cause an over-current condition at
startup. The maximum total capacitance on
the output, including the output filter capacitor
and bulk and decoupling capacitance, at the
load, is given as:
EP5358LUI:
C_{OUT_TOTAL_MAX} = C_{OUT_Filter} + C_{OUT_BULK} = 230uF
EP5358HUI:
C_{OUT_TOTAL_MAX} = C_{OUT_Filter} + C_{OUT_BULK} = 115uF
EP5358LUI in external divider mode:
C_{OUT_TOTAL_MAX} = 2.086x10^-4/V_OUT Farads
The above numbers and formula assume a no
load condition.
Over Current/Short Circuit Protection
The current limit function is achieved by
sensing the current flowing through a sense P-
MOSFET which is compared to a reference
current. When this level is exceeded the P-
FET is turned off and the N-FET is turned on,
pulling V_OUT low. This condition is maintained
for approximately 0.5mS and then a normal
soft start is initiated. If the over current
condition still persists, this cycle will repeat.
EP5358LUI/EP5358HUI
Under Voltage Lockout
During initial power up an under voltage
lockout circuit will hold-off the switching
circuitry until the input voltage reaches a
sufficient level to insure proper operation. If
the voltage drops below the UVLO threshold
the lockout circuitry will again disable the
switching. Hysteresis is included to prevent
chattering between states.
Enable
The ENABLE pin provides a means to shut
down the converter or enable normal
operation. A logic low will disable the
converter and cause it to shut down. A logic
high will enable the converter into normal
operation.
NOTE: The ENABLE pin must not be left
floating.
Thermal Shutdown
When excessive power is dissipated in the
chip, the junction temperature rises. Once the
junction temperature exceeds the thermal
shutdown temperature the thermal shutdown
circuit turns off the converter output voltage
thus allowing the device to cool. When the
junction temperature decreases by 15C°, the
device will go through the normal startup
process.
03541
October 11, 2013
www.altera.com/enpirion Page 10
Rev F