TEA1541 Ver la hoja de datos (PDF) - Philips Electronics
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TEA1541 Datasheet PDF : 19 Pages
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Philips Semiconductors
SMPS control IC with
synchronization function
Product specification
TEA1541
where Vsense(max) is the maximum source voltage for OCP.
ISS flows when the voltage on pin Isense is less than
approximately 0.5 V. If this voltage exceeds 0.5 V, the
soft-start current source starts to limit ISS and completely
switches ISS off at VCC(start).
Note that ISS is derived from the internal current source
supplying charging current to pin VCC. During soft-start,
the charging current to pin VCC will be reduced by up to
60 µA depending on the value of RSS.
6.10 Winding short-circuit protection
The winding short-circuit protection circuit is activated after
the leading edge blanking period. A short-circuit in the
transformer winding is detected when the voltage at
pin Isense exceeds the winding short-circuit protection
voltage Vswp. When a short-circuit is detected, the flyback
converter supply will stop switching. When the voltage at
pin VCC falls below VCC(UVLO), the IC enters safe restart
mode, and capacitor CVCC will recharge via the internal
start-up current source supplied from pin VIN until the
flyback converter supply restarts at VCC(start). The fault
detection and restart cycle will be repeated until the
short-circuit is removed. The winding short-circuit
protection circuit also provides protection if a diode in the
transformer secondary circuit goes short-circuit.
6.11 Overtemperature protection
An accurate temperature protection circuit stops the
converter from switching if the IC junction temperature
exceeds the maximum temperature protection level
Tprot(max). When the voltage at pin VCC falls below
VCC(UVLO), the IC enters safe restart mode, and capacitor
CVCC will recharge to VCC(start) via the internal start-up
current source derived from pin VIN. If the temperature is
still too high, the voltage at pin VCC will fall again to
VCC(UVLO). This cycle is repeated until the junction
temperature falls 8 degrees (typical) below Tprot(max).
period that is longer than the burst standby mode blanking
period tblank(burst).
During a burst standby mode cycle, the soft-start capacitor
CSS, (see Fig.8) is charged to 1.25 V and then discharged
via the soft-start resistor RSS. When CSS is discharged to
0.5 V, a soft-restart is initiated. The frequency of a typical
burst standby mode cycle is approximately: -R----S---S-----1×-----C----S----S-
If, during a burst standby mode cycle, the voltage at
pin VCC falls below the trip level voltage VCC(burst), the IC
will be supplied again from pin VIN. If VCC(UVLO) is reached
within the burst cycle period due to an external load on
pin VCC, a restart cycle begins. If during a burst standby
mode cycle, the voltage on pin VCC stays above the trip
level voltage VCC(burst), a maximum burst efficiency is
obtained because the IC is being consistently powered by
the auxiliary winding.
6.13 Driver
The Gate of the external power MOSFET is driven from a
driver circuit having a current sourcing capability of
typically 100 mA, and a current sink capability of typically
500 mA. This permits fast turn-on and turn-off of the power
MOSFET for efficient operation.
A low driver source current has been chosen in order to
limit the ∆V/∆t at switch-on. This reduces Electro Magnetic
Interference (EMI) and also limits the voltage spikes
across the current sense resistor Rsense.
6.12 Burst standby mode
Pin CTRL and pin Isense are also used to implement the
burst standby mode feature. In burst standby mode, the
converter consumes less than 1 W (typical) of input power
at a maximum output power of 100 mW. This power is
sufficient to supply a low power device such as a
microcontroller. Burst standby mode is entered when a
current larger than the burst standby mode active current
Iburst is forced into pin CTRL, via the opto-coupler, for a
2003 Aug 11
10
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