tea1781 NXP Semiconductors, tea1781 Datasheet - Page 19

• Manufacturer Part Number: tea1781
• Description: Greenchip Pc Secondary Control Ics
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1781_82_1
Preliminary data sheet
7.12.5 Overtemperature protection
The I
the default OCP level is set at 19.5 A. The OCP levels of 3.3 V and 5 V can be increased
by a resistor from pin OCP to ground and decreased by a resistor from pin VDD to pin
OCP.
The 5 V standby OCP level is set to approximately 2.5 A, assuming an inductors series
resistance of 70 m . The OCP_STB level can be increased by a resistor from pin
OCP_STB to ground and decreased by a resistor from pin VDD to pin OCP_STB.
Besides changing the OCP level by a resistor connected to the OCP pin, this level can be
changed by choosing a different series resistance of the output coil.
Whereas an OCP on one of the main outputs results in a latched Protection mode, a 5 V
standby OCP also disables the output but resumes switching at the next cycle when the
output current drops below the OCP level. When the 5 V standby output voltage drops
below its minimum level, because the output current is limited, the system switches to
Standby mode.
The system will enter the Protection mode at an initialized temperature level via an
external NTC network connected to the VNTC pin of the TEA1781T. In this way the
system can be protected against overtemperature.
Fig 16. 3.3 V / 5 V output overcurrent protection
ocp
has a default setting of 100 A. Applying an inductor series resistance of 10 m ,
V
ovp(VOUT_5V)
Protection 5 V
Rev. 01 — 13 February 2009
I
VOUT_5V
Protection mode
I
VOUT_5V
I
ocp
> I
V
TEA1781T; TEA1782T
ocp
ref(OCP)
V
VOUT_5V
GreenChip PC secondary control ICs
Protection 3.3 V
V
ovp(VOUT_3V3)
V
VOUT_3V3
I
VOUT_3V3
Protection mode
© NXP B.V. 2009. All rights reserved.
I
VOUT_3V3
014aaa196
> I
ocp
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