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PDF TEA1795T Data sheet ( Hoja de datos )
| Número de pieza | TEA1795T | |
| Descripción | GreenChip synchronous rectifier controller | |
| Fabricantes | NXP Semiconductors | |
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TEA1795T
GreenChip synchronous rectifier controller
Rev. 1 — 4 November 2010
Product data sheet
1. General description
The TEA1795T is a member of the new generation of Synchronous Rectifier (SR)
controller ICs for switched mode power supplies. Its high level of integration enables the
design of a cost-effective power supply with a minimum number of external components.
The TEA1795T is a dedicated controller IC for synchronous rectification on the secondary
side of resonant converters. It has two driver stages for driving the SR MOSFETs, which
are rectifying the outputs of the central tap secondary transformer windings.
The two gate driver stages have their own sensing inputs and operate independently of
each other.
The TEA1795T is fabricated in a Silicon On Insulator (SOI) process.
2. Features and benefits
2.1 Distinctive features
Accurate synchronous rectification functionality
Wide supply voltage range (8.5 V to 38 V)
Separate sense inputs for sensing the drain and source voltage of each SR MOSFET
High level of integration, resulting in a minimum external component count
High driver output voltage of 10 V to drive all MOSFET brands to the lowest RDSon
2.2 Green features
Low current consumption
High system efficiency from no load to full load
2.3 Protection features
UnderVoltage Protection (UVP)
3. Applications
The TEA1795T is intended for resonant power supplies. In such applications, it can drive
two external synchronous rectifier MOSFETs which replace diodes for the rectification of
the voltages on the two secondary windings of the transformer. It can be used in
applications such as:
Adapters
ATX power supplies
1 page  
NXP Semiconductors
TEA1795T
GreenChip synchronous rectifier controller
The zero current is detected by sensing a Vdeact(drv) (−12 mV typical) difference between
the drain sense pins and the source sense pins (see Figure 4). A synchronous
rectification off-timer (toff(sr)(min), 400 ns typical) is started and the next switching cycle can
only be started when the synchronous rectification off-timer has finished.
secondary
current
drain sense-
source sense
voltage
0A
0V
Vdeact(drv)
Vreg(drv)
Vact(drv)
gate driver
0V
blanking
windows
tact(sr)(min)
Fig 4. Synchronous rectification signals
toff(sr)(min)
t
001aal798
7.5 Gate driver (GDA and GDB pins)
The gate driver circuit to the gate of the external SR MOSFET has a source capability of
typically 400 mA and a sink capability of typically 2.7 A. This allows fast turn-on and
turn-off of the external SR MOSFET for efficient operation. The source stage is coupled to
the timer (see Figure 1). When the timer has finished, the source capability is reduced to a
small current (4 mA typical) capable of keeping the driver output voltage at its level.
The output voltage of the driver is limited to 10 V (typical). This high output voltage drives
all MOSFET brands to the minimum on-state resistance.
During start-up conditions (VCC < Vstartup) and UVLO the driver output voltage is actively
pulled low.
7.6 Source sense (SSA and SSB pins)
The IC is equipped with additional source sense pins (SSA and SSB). These pins are
used for the measurement of the drain-to-source voltage of the external SR MOSFET.
This drain-to-source voltage determines the timing of the gate driver. The source sense
input should be connected as close as possible to the source pin of the external
SR MOSFET to minimize timing errors, caused by voltage difference on PCB tracks, due
to parasitic inductance in combination with large dI/dt values.
TEA1795T
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 4 November 2010
© NXP B.V. 2010. All rights reserved.
5 of 14
5 Page 
NXP Semiconductors
TEA1795T
GreenChip synchronous rectifier controller
13. Revision history
Table 6. Revision history
Document ID
Release date
TEA1795T v.1
20101104
Data sheet status
Product data sheet
Change notice
-
Supersedes
-
TEA1795T
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 4 November 2010
© NXP B.V. 2010. All rights reserved.
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