TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 8 of 13
NXP Semiconductors
TEA1761T
GreenChip synchronous rectifier controller
[1] The V
CC
stop voltage is V
startup
− V
hys
.
11. Application information
A switched mode power supply with the TEA1761T consists of a primary side
discontinuous conduction mode flyback controller, a transformer, and an output stage with
a feedback circuit. In the output stage a MOSFET (Qsec) is used for low conduction
losses. The MOSFET is controlled by the TEA1761T. The output voltage and/or current is
also controlled by the TEA1761T via the opto coupler connection to the primary side. See
Figure 5.
The output voltage is set by resistors Rfb1 and Rfb2. The output current is controlled by
the resistor Risense. The timing for the synchronous rectifier switch is derived from the
voltage sensed on the SRSENSE pin. The resistor in the SRSENSE connection is needed
to protect the TEA1761T from excessive voltages. The SRSENSE resistor should typically
be 1 kΩ. Higher values might impair correct timing, lower values may not provide sufficient
protection.
Opto output (pin OPTO)
I
O(max)
maximum output current V
OPTO
>5V 4 5 12 mA
V
O(min)
minimum output voltage I
OPTO
= 4 mA - - 3.5 V
Voltage sense (pin VSENSE)
V
reg(VSENSE)
regulation voltage on pin
VSENSE
See Figure 4 2.475 2.5 2.525 V
I
I(VSENSE)
input current on pin
VSENSE
V
VSENSE
=V
reg(VSENSE)
−100 0 +100 nA
g
m
transconductance V
VSENSE
to I
OPTO
- 40 - A/V
GB gain bandwidth product R
L
=1kΩ 1 MHz
Current sense (pin ISENSE)
V
reg(ISENSE)
regulation voltage on pin
ISENSE
46 50 54 mV
I
I(reg)(ISENSE)
regulation input current
on pin ISENSE
V
ISENSE
=V
reg(ISENSE)
−200 −100 0 nA
g
m
transconductance V
ISENSE
to I
OPTO
- 15 - A/V
GB gain bandwidth product R
L
=1kΩ 1 - - MHz
Temperature protection
T
pl(max)
maximum protection
level temperature
140 150 - °C
T
pl(hys)
protection level
hysteresis temperature
-12-°C
Table 5. Characteristics
…continued
T
amb
=25
°
C; V
CC
= 20 V; all voltages are measured with respect to ground (pin 2); currents are positive when flowing into
the IC; unless otherwise specified.
Symbol Parameter Conditions Min Typ Max Unit
