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TEA1795T/N1,118

P1-P3P4-P6P7-P9P10-P12P13-P14
TEA1795T All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
Product data sheet Rev. 1 — 4 November 2010 4 of 14
NXP Semiconductors
TEA1795T
GreenChip synchronous rectifier controller
7.2 Start-up and UnderVoltage LockOut (UVLO)
The IC leaves the UVLO state and activates the synchronous rectifier circuitry when the
voltage on the V
CC
pin is above V
startup
(8.5 V typical). When the voltage drops below
8.0 V (typical), the UVLO state is reentered and the SR MOSFET gate driver outputs are
actively kept low.
7.3 Supply management
All (internal) reference voltages are derived from a temperature compensated, on-chip
band gap circuit.
7.4 Synchronous rectification (DSA, SSA, DSB and SSB pins)
The voltages present between the drain and source terminals of the SR MOSFETs are
used to derive the timing for the gate drive signal. The IC senses the voltage difference
between the drain sense (pins DSA and DSB) and the source sense (pins SSA and SSB)
connections. When this voltage difference is lower than V
act(drv)
(−220 mV typical), the
corresponding gate driver output voltage is driven high and the external SR MOSFET is
switched on.
When the external SR MOSFET is switched on, the input signals on the drain sense pins
and source sense pins are ignored during the minimum synchronous rectification active
time (t
act(sr)(min)
, 520 ns typical). This minimizes false switch-off due to the sensing of high
frequency ringing signals at the start of the conduction phase.
Once this minimum synchronous rectification active time has ended, the IC monitors the
difference between the drain sense inputs and the source sense inputs. When the
difference is higher than V
reg(drv)
(−25 mV typical), the gate driver output voltage is
regulated to maintain this −25 mV difference between the drain sense pins and the source
sense pins. As a result, the SR MOSFET can be switched off quickly when the current
through the external SR MOSFET reaches zero.
Fig 3. TEA1795T: typical configuration
001aal79
7
DSA
GDA
SSA
DSB
V
CC
GDB
SSB
GND
Q
prim1
C
HB
R
DRNSENSE1
Q
prim2
Q
sec1
PRIMARY
SIDE
CONTROLLER
TEA1795T
V
in
V
out
TR
IC1
R
DRNSENSE2
Q
sec2
C
out
TEA1795T All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
Product data sheet Rev. 1 — 4 November 2010 5 of 14
NXP Semiconductors
TEA1795T
GreenChip synchronous rectifier controller
The zero current is detected by sensing a V
deact(drv)
(−12 mV typical) difference between
the drain sense pins and the source sense pins (see Figure 4
). A synchronous
rectification off-timer (t
off(sr)(min)
, 400 ns typical) is started and the next switching cycle can
only be started when the synchronous rectification off-timer has finished.
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 (V
CC
<V
startup
) 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.
Fig 4. Synchronous rectification signals
001aal79
8
t
act(sr)(min)
t
off(sr)(min)
secondary
current
0 A
0 V
V
deact(drv)
V
reg(drv)
V
act(drv)
0 V
t
drain sense-
source sense
voltage
gate driver
blanking
windows
TEA1795T All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
Product data sheet Rev. 1 — 4 November 2010 6 of 14
NXP Semiconductors
TEA1795T
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
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. 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
V
CC
supply voltage continuous −0.4 +38 V
V
sense(D)A
drain sense voltage A continuous - 120 V
V
sense(D)B
drain sense voltage B continuous - 120 V
Currents
I
drv(G)A
gate driver current A δ <10% −0.8 +3.0 A
I
drv(G)B
gate driver current B δ <10% −0.8 +3.0 A
I
I(DSA)
input current on pin DSA −3- mA
I
I(DSB)
input current on pin DSB −3- mA
I
I(SSA)
input current on pin SSA −1+1mA
I
I(SSB)
input current on pin SSB −1+1mA
General
P
tot
total power dissipation T
amb
<80°C - 0.45 W
T
stg
storage temperature −55 +150 °C
T
j
junction temperature −40 +150 °C
ElectroStatic Discharge voltage (ESD)
V
ESD
electrostatic discharge
voltage
class 2
human body
model
[1]
- 2000 V
machine model
[2]
-200V
charged device
model
-500V
Table 4. Thermal characteristics
Symbol Parameter Conditions Typ Unit
R
th(j-a)
thermal resistance from junction
to ambient
JEDEC test board 150 K/W
R
th(j-c)
thermal resistance from junction
to case
JEDEC test board 100 K/W
P1-P3P4-P6P7-P9P10-P12P13-P14

TEA1795T/N1,118

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Buy TEA1795T/N1,118
Manufacturer:
NXP Semiconductors
Description:
Switching Controllers 10V 2.7A 500KHz
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