1. General description
The TEA1761T is a member of the new generation of Synchronous Rectifier (SR)
controller ICs for switched mode power supplies. Its high level of integration allows the
design of a cost-effective power supply with a very low number of external components.
The TEA1761T is a controller IC dedicated for synchronous rectification on the secondary
side of discontinuous conduction mode and quasi resonant flyback converters. Besides
electronics for synchronous rectification, it also has integrated circuitry for output voltage
and output current regulation.
The TEA1761T is fabricated in a Silicon On Insulator (SOI) process. This NXP SOI
process makes possible a wide range of operation.
2. Features
2.1 Distinctive features
nCombined synchronous rectification and primary feedback control functionality
nWide supply voltage range (8.6 V to 38 V)
nHigh level of integration, resulting in a very low external component count
nWide opto coupler output voltage range (3.5 V to 38 V)
nAccurate internal voltage reference for voltage control (within 1 %)
nHigh driver output voltage of 10 V to drive all MOSFET brands to the lowest RDSon
2.2 Green features
nLow current consumption
nHigh system efficiency from no load to full load
2.3 Protection features
nUndervoltage protection
nInternal over-temperature protection
3. Applications
The TEA1761T is intended for adapters. The device can also be used in all other
discontinuous conduction mode and quasi resonant flyback systems that demand a highly
efficient and cost-effective solution.
TEA1761T
GreenChip synchronous rectifier controller
Rev. 02 — 25 April 2007 Product data sheet
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 2 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
4. Ordering information
5. Block diagram
Table 1. Ordering information
Type number Package
Name Description Version
TEA1761T/N2 SO8 plastic small outline package; 8 leads; body width 3.9 mm SOT96-1
Fig 1. TEA1761T block diagram
014aaa056
2.5 V
OVER
TEMPERATURE
PROTECTION
VCC
OPTO
VSENSE
8
3
n.c.
2
GND
5
SRSENSE 1
4
R
S
Q
Q
6
50 mV
−55 mV
DRIVER
control
ISENSE
7
−12 mV−310 mV
TIMER
2 µs
2.2 µs
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 3 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
6. Pinning information
6.1 Pinning
6.2 Pin description
7. Functional description
The TEA1761T is the controller for synchronous rectification to be used in discontinuous
conduction mode and quasi resonant flyback converters. Besides controlling the
SR MOSFET, the TEA1761T contains the voltage reference and amplifiers to regulate and
control the output voltage and current of the power supply.
7.1 Start-up and undervoltage lock out
The IC leaves the under-voltage lock-out state and activates the synchronous rectifier
circuitry and also the voltage/current sense circuitry as soon as the voltage on the VCC pin
is above 8.6 V (typical). As soon as the voltage drops below 8.1 V (typical), the
under-voltage lock-out state is re-entered and the SR driver output is actively kept low and
also the opto driver output is disabled.
7.2 Synchronous rectification
After a negative voltage (−310 mV typical) is sensed on the SRSENSE pin, the driver
output voltage is made high and the external MOSFET is switched on. As soon as the
SRSENSE voltage rises to −55 mV, the driver output voltage is regulated to maintain the
−55 mV on the SRSENSE pin. As soon as the SRSENSE voltage is above −12 mV, the
Fig 2. Pin configuration for TEA1761T
TEA1761T
SRSENSE VCC
GND ISENSE
n.c. VSENSE
DRIVER OPTO
001aae772
1
2
3
4
6
5
8
7
Table 2. Pin description
Symbol Pin Description
SRSENSE 1 synchronous timing input
GND 2 ground
n.c. 3 not connected
DRIVER 4 driver output for SR MOSFET
OPTO 5 opto coupler driver output
VSENSE 6 sense input for voltage control
ISENSE 7 sense input for current control
VCC 8 supply voltage
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 4 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
driver output is pulled to ground. After switch-on of the SR MOSFET, the input signal on
the SRSENSE pin is blanked for 2 µs (typical). This will eliminate false switch-off due to
high frequency ringing at the start of the secondary stroke.
Because the driver output voltage is reduced as soon as the voltage on the SRSENSE pin
is −55 mV, the external power switch can be switched off fast when the current through the
switch reaches zero. With this zero-current switch off, no separate standby mode is
needed to maintain high efficiency during no-load operation. The zero current is detected
by sensing a −12 mV level on the SRSENSE pin. See Figure 3.
If the secondary stroke of the flyback converter is shorter than 2 µs (typical), the driver
output is disabled. This will guarantee stable operation for very low duty cycles. When the
secondary stroke increases above 2.2 µs (typical) then the driver output is again enabled.
7.3 SMPS output voltage and current regulation
The output voltage of the flyback Switched Mode Power Supply (SMPS) can be controlled
by sensing the output voltage via pin VSENSE. The feedback loop via the primary controller
can regulate the output voltage of the switched mode power supply by regulating the
voltage on pin VSENSE, to 2.5 V.
Also the output current of the flyback SMPS can be controlled or limited. The voltage on
pin ISENSE is regulated or limited to 50 mV above the voltage on pin GND.
Fig 3. Synchronous rectification signals
014aaa057
0 V
−12 mV
−55 mV
−310 mV
0 A
0 A
0 V
VSRSENSE
VDRIVER
Primary
current
Secondary
current
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 5 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
7.4 Opto output
The opto output is intended to drive an opto coupler (see Figure 5). The opto output has
an open-drain output configuration. The maximum sink current is internally limited to 5 mA
(typical). The output is linearly controlled via the VSENSE and ISENSE input pins. An
over-temperature situation will switch the opto output to its maximum sink current.
During start-up (VCC <V
startup) and undervoltage lock-out the output is disabled.
7.5 Supply management
All (internal) reference voltages are derived from a temperature compensated, on-chip
band gap circuit. The reference voltage is trimmed to an accuracy within 1 %.
7.6 OverTemperature Protection (OTP)
The IC provides an accurate internal overtemperature protection of 150 °C (typical). The
IC will maximize the current of pin OPTO as soon as the internal temperature limit is
reached. The opto signal can be used on the primary side of the flyback controller to
activate the SMPS protection or limit the output power. As soon as the overtemperature
condition is solved, normal operation will resume.
7.7 Driver
The driver circuit to the gate of the external power MOSFET has a source capability of
typically 250 mA and a sink capability of typically 2.7 A. This permits fast turn-on and
turn-off of the power MOSFET for efficient operation. The output voltage of the driver is
limited to 10 V (typical). This high output voltage will drive all MOSFET brands to the
minimum on-state resistance.
During start-up conditions (VCC <V
startup) and undervoltage lock-out the driver output
voltage is actively pulled low.
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 6 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
8. Limiting values
[1] Equivalent to discharging a 100 pF capacitor through a 1.5 kΩ series resistor.
[2] Equivalent to discharging a 200 pF capacitor through a 0.75 µH coil and a 10 Ω resistor.
9. Thermal characteristics
The graph in Figure 4 shows the relationship between junction temperature and VSENSE
voltage.
Table 3. Limiting values
In accordance with the Absolute Maximum Rating System (IEC 60134). All voltages are measured with respect to ground
(pin 2); positive currents flow into the chip. The voltage ratings are valid provided other ratings are not violated; current ratings
are valid provided the other ratings are not violated.
Symbol Parameter Conditions Min Max Unit
Voltages
VCC supply voltage continuous −0.4 +38 V
VOPTO voltage on pin OPTO continuous −0.4 +38 V
VSRSENSE voltage on pin SRSENSE continuous - 120 V
VVSENSE voltage on pin VSENSE continuous −0.4 +5 V
VISENSE voltage on pin ISENSE −0.4 +5 V
Currents
IOPTO current on pin OPTO - 12 mA
IDRIVER current on pin DRIVER duty cycle < 10 % −0.8 +3 A
ISRSENSE current on pin SRSENSE −3- mA
General
Ptot total power dissipation Tamb <80°C - 0.45 W
Tstg storage temperature −55 +150 °C
Tjjunction temperature −20 +150 °C
ESD
VESD electrostatic discharge voltage class 2
human body model [1] - 2000 V
machine model [2] - 200 V
charged device model - 500 V
Table 4. Thermal characteristics
Symbol Parameter Conditions Typ Unit
Rth(j-a) thermal resistance from junction to ambient in free air 150 K/W
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 7 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
10. Characteristics
Fig 4. Typical regulated VSENSE voltage versus junction temperature
junction temperature (°C)
−50 150100050
001aae779
2480
2520
2440
2600
regulated
VSENSE
voltage
(mV)
2400
Table 5. Characteristics
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
Supply voltage management (pin VCC)
Vstartup start-up voltage 8.35 8.6 8.85 V
Vhys hysteresis voltage [1] 0.5 V
ICC(oper) operating supply current VCC = 8 V (VCC <V
startup)-1-mA
under normal operation; no load on
pin DRIVER - 1.4 - mA
Synchronous rectification sense input (pin SRSENSE)
Vact(drv) driver activation voltage −340 −310 −280 mV
Vreg(drv) driver regulation voltage −65 −55 −45 mV
Vdeact(drv) driver deactivation
voltage −12 mV
td(act)(drv) driver activation delay
time - 125 - ns
tact(sr)(min) minimum synchronous
rectification active time Short time 1.5 2 2.5 µs
Long time 1.7 2.2 2.7 µs
Driver (pin DRIVER)
Isource source current VCC = 15 V; voltage on pin DRIVER = 2 V −0.3 −0.25 −0.2 A
Isink sink current VCC =15V;
voltage on pin DRIVER = 2 V 1 1.4 - A
voltage on pin DRIVER = 9.5 V 2.2 2.7 - A
Vo(max) maximum output voltage VCC =15V - 10 12 V
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 VCC stop voltage is Vstartup −Vhys.
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)
IO(max) maximum output current VOPTO >5V 4 5 12 mA
VO(min) minimum output voltage IOPTO = 4 mA - - 3.5 V
Voltage sense (pin VSENSE)
Vreg(VSENSE) regulation voltage on pin
VSENSE See Figure 4 2.475 2.5 2.525 V
II(VSENSE) input current on pin
VSENSE VVSENSE =V
reg(VSENSE) −100 0 +100 nA
gmtransconductance VVSENSE to IOPTO - 40 - A/V
GB gain bandwidth product RL=1kΩ1 MHz
Current sense (pin ISENSE)
Vreg(ISENSE) regulation voltage on pin
ISENSE 46 50 54 mV
II(reg)(ISENSE) regulation input current
on pin ISENSE VISENSE =V
reg(ISENSE) −200 −100 0 nA
gmtransconductance VISENSE to IOPTO - 15 - A/V
GB gain bandwidth product RL=1kΩ1 - - MHz
Temperature protection
Tpl(max) maximum protection
level temperature 140 150 - °C
Tpl(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
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 9 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
12. Test information
12.1 Quality information
The
General Quality Specification for Integrated Circuits, SNW-FQ-611
is applicable.
Fig 5. Application example TEA1761T
001aae775
DRIVER
SRSENSE
OPTO VCC VSENSE
Vout
ISENSEGND
TEA1761T
PRIMARY
SIDE
CONTROLLER
OPTO
Vin
Qprim Qsec
Ropto
Rfb1
Rfb2
Cout
Cfb
TR
Rsrsense
Risense
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 10 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
13. Package outline
Fig 6. Package outline SOT96-1 (SO8)
UNIT A
max. A1A2A3bpcD
(1) E(2) (1)
eH
ELL
pQZywv θ
REFERENCES
OUTLINE
VERSION EUROPEAN
PROJECTION ISSUE DATE
IEC JEDEC JEITA
mm
inches
1.75 0.25
0.10 1.45
1.25 0.25 0.49
0.36 0.25
0.19 5.0
4.8 4.0
3.8 1.27 6.2
5.8 1.05 0.7
0.6 0.7
0.3 8
0
o
o
0.25 0.10.25
DIMENSIONS (inch dimensions are derived from the original mm dimensions)
Notes
1. Plastic or metal protrusions of 0.15 mm (0.006 inch) maximum per side are not included.
2. Plastic or metal protrusions of 0.25 mm (0.01 inch) maximum per side are not included.
1.0
0.4
SOT96-1
X
wM
θ
A
A1
A2
bp
D
HE
Lp
Q
detail X
E
Z
e
c
L
vMA
(A )
3
A
4
5
pin 1 index
1
8
y
076E03 MS-012
0.069 0.010
0.004 0.057
0.049 0.01 0.019
0.014 0.0100
0.0075 0.20
0.19 0.16
0.15 0.05 0.244
0.228 0.028
0.024 0.028
0.012
0.010.010.041 0.004
0.039
0.016
0 2.5 5 mm
scale
SO8: plastic small outline package; 8 leads; body width 3.9 mm SOT96-1
99-12-27
03-02-18
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 11 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
14. Revision history
Table 6. Revision history
Document ID Release date Data sheet status Change notice Supersedes
TEA1761T_2 20070425 Product data sheet - TEA1761T_1
Modifications: •Updated limiting values for VSRSENSE in Table 3.
•Updated characteristic values for Isource and Isink in Table 5.
•Added footnote [1] to Table 5.
•Soldering section removed.
•The format of this data sheet has been redesigned to comply with the new identity guidelines
of NXP Semiconductors.
•Legal texts have been adapted to the new company name where appropriate.
TEA1761T_1 20060331 Objective data sheet - -
TEA1761T_2 © NXP B.V. 2007. All rights reserved.
Product data sheet Rev. 02 — 25 April 2007 12 of 13
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
15. Legal information
15.1 Data sheet status
[1] Please consult the most recently issued document before initiating or completing a design.
[2] The term ‘short data sheet’ is explained in section “Definitions”.
[3] The product status of device(s) described in this document may have changed since this document was published and may differ in case of multiple devices. The latest product status
information is available on the Internet at URL http://www.nxp.com.
15.2 Definitions
Draft — The document is a draft version only. The content is still under
internal review and subject to formal approval, which may result in
modifications or additions. NXP Semiconductors does not give any
representations or warranties as to the accuracy or completeness of
information included herein and shall have no liability for the consequences of
use of such information.
Short data sheet — A short data sheet is an extract from a full data sheet
with the same product type number(s) and title. A short data sheet is intended
for quick reference only and should not be relied upon to contain detailed and
full information. For detailed and full information see the relevant full data
sheet, which is available on request via the local NXP Semiconductors sales
office. In case of any inconsistency or conflict with the short data sheet, the
full data sheet shall prevail.
15.3 Disclaimers
General — Information in this document is believed to be accurate and
reliable. However, NXP Semiconductors does not give any representations or
warranties, expressed or implied, as to the accuracy or completeness of such
information and shall have no liability for the consequences of use of such
information.
Right to make changes — NXP Semiconductors reserves the right to make
changes to information published in this document, including without
limitation specifications and product descriptions, at any time and without
notice. This document supersedes and replaces all information supplied prior
to the publication hereof.
Suitability for use — NXP Semiconductors products are not designed,
authorized or warranted to be suitable for use in medical, military, aircraft,
space or life support equipment, nor in applications where failure or
malfunction of a NXP Semiconductors product can reasonably be expected to
result in personal injury, death or severe property or environmental damage.
NXP Semiconductors accepts no liability for inclusion and/or use of NXP
Semiconductors products in such equipment or applications and therefore
such inclusion and/or use is at the customer’s own risk.
Applications — Applications that are described herein for any of these
products are for illustrative purposes only. NXP Semiconductors makes no
representation or warranty that such applications will be suitable for the
specified use without further testing or modification.
Limiting values — Stress above one or more limiting values (as defined in
the Absolute Maximum Ratings System of IEC 60134) may cause permanent
damage to the device. Limiting values are stress ratings only and operation of
the device at these or any other conditions above those given in the
Characteristics sections of this document is not implied. Exposure to limiting
values for extended periods may affect device reliability.
Terms and conditions of sale — NXP Semiconductors products are sold
subject to the general terms and conditions of commercial sale, as published
at http://www.nxp.com/profile/terms, including those pertaining to warranty,
intellectual property rights infringement and limitation of liability, unless
explicitly otherwise agreed to in writing by NXP Semiconductors. In case of
any inconsistency or conflict between information in this document and such
terms and conditions, the latter will prevail.
No offer to sell or license — Nothing in this document may be interpreted
or construed as an offer to sell products that is open for acceptance or the
grant, conveyance or implication of any license under any copyrights, patents
or other industrial or intellectual property rights.
15.4 Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
GreenChip — is a trademark of NXP B.V.
16. Contact information
For additional information, please visit: http://www.nxp.com
For sales office addresses, send an email to: salesaddresses@nxp.com
Document status[1][2] Product status[3] Definition
Objective [short] data sheet Development This document contains data from the objective specification for product development.
Preliminary [short] data sheet Qualification This document contains data from the preliminary specification.
Product [short] data sheet Production This document contains the product specification.
NXP Semiconductors TEA1761T
GreenChip synchronous rectifier controller
© NXP B.V. 2007. All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: salesaddresses@nxp.com
Date of release: 25 April 2007
Document identifier: TEA1761T_2
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
17. Contents
1 General description. . . . . . . . . . . . . . . . . . . . . . 1
2 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.1 Distinctive features . . . . . . . . . . . . . . . . . . . . . . 1
2.2 Green features . . . . . . . . . . . . . . . . . . . . . . . . . 1
2.3 Protection features . . . . . . . . . . . . . . . . . . . . . . 1
3 Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
4 Ordering information. . . . . . . . . . . . . . . . . . . . . 2
5 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 2
6 Pinning information. . . . . . . . . . . . . . . . . . . . . . 3
6.1 Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
6.2 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . 3
7 Functional description . . . . . . . . . . . . . . . . . . . 3
7.1 Start-up and undervoltage lock out. . . . . . . . . . 3
7.2 Synchronous rectification . . . . . . . . . . . . . . . . . 3
7.3 SMPS output voltage and current regulation . . 4
7.4 Opto output. . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
7.5 Supply management. . . . . . . . . . . . . . . . . . . . . 5
7.6 OverTemperature Protection (OTP) . . . . . . . . . 5
7.7 Driver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8 Limiting values. . . . . . . . . . . . . . . . . . . . . . . . . . 6
9 Thermal characteristics. . . . . . . . . . . . . . . . . . . 6
10 Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . 7
11 Application information. . . . . . . . . . . . . . . . . . . 8
12 Test information. . . . . . . . . . . . . . . . . . . . . . . . . 9
12.1 Quality information . . . . . . . . . . . . . . . . . . . . . . 9
13 Package outline . . . . . . . . . . . . . . . . . . . . . . . . 10
14 Revision history. . . . . . . . . . . . . . . . . . . . . . . . 11
15 Legal information. . . . . . . . . . . . . . . . . . . . . . . 12
15.1 Data sheet status . . . . . . . . . . . . . . . . . . . . . . 12
15.2 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
15.3 Disclaimers. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
15.4 Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 12
16 Contact information. . . . . . . . . . . . . . . . . . . . . 12
17 Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
