tea1738t NXP Semiconductors, tea1738t Datasheet - Page 5

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

NXP Semiconductors
7. Functional description
TEA1738T_TEA1738LT
Product data sheet
Fig 3.
Typical configuration
D1
R3
7.1 General control
7.2 Start-up and UnderVoltage LockOut (UVLO)
The TEA1738(L) contains a flyback circuit controller, a typical configuration of which is
shown in
Initially, the capacitor on the VCC pin is charged from the high voltage mains via resistor
R3.
If V
reaches V
and for pin PROTECT to reach the V
reached, the IC charges the ISENSE pin to the V
typical application the supply voltage is taken over by the auxiliary winding of the
transformer.
If a protection is triggered the controller stops switching. Depending on the protection
triggered it either causes a restart or latches the converter to an off-state.
A restart caused by a protection rapidly charges the OPTIMER pin to 4.5 V (typical). The
TEA1738(L) enters Power-down mode until the OPTIMER pin discharges down to
1.2 V (typical). In Power-down mode, the IC consumes a very low supply current
(10 μA typical) and the VCC pin is clamped at 22 V (typical) by an internal clamp circuit.
When the voltage on pin OPTIMER drops below 1.2 V (typical) and the VCC pin voltage is
above the VCC start-up voltage (see
When a latched protection is triggered, the TEA1738(L) immediately enters Power-down
mode. The VCC pin is clamped to a voltage just above the latch protection reset voltage
(V
Θ
C1
O1
C2
R2
rst(latch)
R4
CC
is lower than V
R1
+ 1 V).
Figure
startup
VINSENSE
PROTECT
OPTIMER
C4
CTRL
All information provided in this document is subject to legal disclaimers.
the IC first waits for pin VINSENSE to reach the V
3.
R8
5
6
7
8
startup
Rev. 2 — 14 January 2011
TEA1738LT
TEA1738T
, the IC current consumption is low (10 μA typical). When V
4
3
2
1
ISENSE
VCC
DRIVER
GND
det(L)(PROTECT)
Figure
C5
TEA1738T; TEA1738LT
4), the IC restarts.
R10
start(soft)
R6
C6
D2
voltage. When both levels are
S1
level and starts switching. In a
R9
GreenChip SMPS control IC
T1
start(VINSENSE)
D3
© NXP B.V. 2011. All rights reserved.
C7
001aan169
voltage
Z1
O1
5 of 21
CC