tea1738t NXP Semiconductors, tea1738t Datasheet - Page 6

• Manufacturer Part Number: tea1738t
• Description: Tea1738t; Tea1738lt Greenchip Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1738T_TEA1738LT
Product data sheet
7.3 Supply management
7.4 OverVoltage Protection (VCC pin)
7.5 Input voltage detection (VINSENSE pin)
When the voltage on pin VCC drops below the V
controller stops switching and the TEA1738T enters Restart mode. In Restart mode the
driver output is disabled and the VCC pin voltage is recharged via resistor R3 to the
rectified mains voltage. For the TEA1738LT a VCC undervoltage, which does not occur
during a start-up event, latches the IC in an off-state.
All internal reference voltages are derived from a temperature compensated on-chip band
gap circuit. Internal reference currents are derived from a trimmed and temperature
compensated current reference circuit.
An OVP circuit is connected to the VCC pin. After 8 consecutive OVP cycles the IC
triggers the latched protection. When V
is reached, the counter is reset to zero.
If a lower overvoltage protection level is needed, a Zener diode can be connected
between the VCC pin and the PROTECT pin.
In a typical application the mains input voltage can be detected by the VINSENSE pin.
Switching does not take place until the voltage on VINSENSE has reached the
V
When during operation the VINSENSE voltage drops below V
(0.72 V typical), the converter stops switching and performs a restart.
An internal clamp of 5.2 V (typical) protects this pin from excessive voltages.
Fig 4.
start(VINSENSE)
VINSENSE
PROTECT
OPTIMER
ISENSE
Start-up sequence, normal operation and restart sequence
charging VCC
V
V
CC
capacitor
O
voltage (0.94 V typical).
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 14 January 2011
converter
starting
soft start
operation
normal
CC
TEA1738T; TEA1738LT
drops below the V
(power-down)
protection
th(UVLO)
level during normal operation, the
restart
th(OVP)
GreenChip SMPS control IC
det(L)(VINSENSE)
001aan170
voltage before count=8
soft start
V
V
V
V
V
V
4.5 V
1.2 V
© NXP B.V. 2011. All rights reserved.
startup
th(UVLO)
start(VINSENSE)
det(L)(VINSENSE)
det(H)(PROTECT)
det(L)(PROTECT)
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