Application Notes

AN11045
Next generation of NXP low VCEsat transistors: improved
technology for discrete semiconductors
Rev. 3 — 28 February 2013
Application note
Document information
Info
Content
Keywords
Breakthrough In Small Signal (BISS) transistor, low VCEsat, load switch,
DC-to-DC converter
Abstract
This application note contains detailed information about the latest
generation of low VCEsat transistors providing a further improvement in
performance. This opens a new field of applications for bipolar transistors
with higher power requirements and improved energy efficiency.
AN11045
NXP Semiconductors
Next generation of NXP low VCEsat transistors
Revision history
Rev
Date
Description
3
20130228
Added Table 5 and Table 6
2
20110623
Table 3: corrected mounting area.
1
20110525
Initial version
Contact information
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
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1. Introduction
The performance of bipolar transistors has significantly improved in recent years. The
collector-emitter saturation resistance has been reduced towards values which were
known from MOSFETs only. NXP Semiconductors latest generation of medium-power low
collector-emitter saturation voltage VCEsat transistors in Surface-Mounted Design (SMD)
packages opens a new field of applications. Switching applications with higher power and
current requirements can also be realized, while the overall efficiency is further improved.
In the last years switching applications for higher power ratings are realized with
MOSFETs as switching elements in most cases because the low drain-source on-state
resistance RDSon values together with fast switching times guarantee low losses.
Furthermore MOSFETs do not require a static control current.
Nowadays there is a revival of bipolar transistors in load switch and charging applications
for mobile equipment in the area of communication and consumer applications. The
residual on-state resistance of the latest generation bipolar transistors has become
comparable to MOSFETs in the same package. Due to a high and constant current
amplification, rather small base currents are sufficient to control the Bipolar junction
transistor (BJT) switches. Although the bipolar technology has the disadvantage of the
current-based control, there are important advantages such as ElectroStatic
Discharge (ESD) robustness and an inherent backward current blocking. The temperature
stability of some important key parameters is higher for bipolar transistors than for
MOSFETs. The base-emitter voltage VBE has a temperature coefficient of about 2 mV/K,
whereas the gate-source threshold voltage VGS(th) changes with a factor of about 4 mV/K
to 6 mV/K. The same holds for the on-state resistance. The collector-emitter saturation
resistance RCEsat decreases with about 0.4 %/K over temperature, the drain-source
on-state resistance RDSon of a MOSFET increases with a factor of about 0.6 %/K.
NXP Semiconductors developed a new architecture for its fourth generation of
low VCEsat Breakthrough In Small Signal (BISS) transistors. The medium-power
transistors in SMD packages mark a new milestone in performance, expanding the
spectrum of applications.
2. Higher performance for low VCEsat BISS transistors
2.1 Technological background of low VCEsat transistors
The major contribution to the power dissipation of a bipolar transistor in a switching
application is the collector current related loss, which can be calculated as
PC = VCEsat  IC. The current depends on the application, this means on the resistance of
the load and the supply voltage. Therefore the minimum residual voltage measured
between collector and emitter when the transistor is driven in a saturated condition is the
only choice for a designer to improve the power efficiency. Transistors developed with the
target to achieve a very low saturation voltage are called low VCEsat transistors. In the
design of the die, the emitter region is spread across a large area. The layout of the base
contact has a geometry which enables an even and efficient drive for the whole active
area. Low VCEsat transistors show a so-called mesh-design, in which the transistor is
separated into many corresponding cell structures. Transistors with this topology have an
outstanding performance regarding VCEsat and also show a high and constant current
amplification.
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Figure 1 to Figure 4 show the die layout of the four generations of NXP BISS transistors.
The generations BISS-3 and specifically BISS-4 show an even more efficient use of the
emitter area and a higher number of corresponding cell structures.
006aac619
Fig 1.
Die layout of a BISS first generation
006aac620
Fig 2.
Die layout of a BISS second generation
006aac621
Fig 3.
Die layout of a BISS third generation
AN11045
Application note
006aac622
Fig 4.
Die layout of a BISS fourth generation
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2.2 BISS-4: a milestone in the development of medium-power bipolar
transistors
The development of a new family of medium-power bipolar transistors requires a review of
the whole architecture of the transistor: the chip design itself, the choice of material, the
metallization of the chip, the connection between chip and package, the bonding and the
consideration of the aspects of the different packages. All of these items contribute to the
overall collector-emitter resistance which can be achieved for the final component.
The BISS-4 product portfolio has two branches. The first focuses on an ultra low VCEsat
performance in order to minimize the saturation resistance as much as possible. The
target for the development was to reach an RCEsat as low as 14 m in SMD packages.
This is an on-state resistance seen previously only in advanced MOSFETs. The second
branch was designed for high-speed switching applications. In addition to the reduction of
RCEsat, short switching and storage times were an important target for development.
A requirement of the architecture of the products from both branches was the possibility to
integrate it into a wide range of SMD packages. The target packages were SOT23,
SOT457 (SC-74), SOT223, SOT89 and SOT96 (SO-8). This large portfolio enables the
implementation of transistors into various applications. A cost-effective mass production
with high volume and a good delivery performance can be ensured by this approach. The
NXP low VCEsat transistors are qualified according to AEC-Q101 and are suitable for
applications in the automotive area, as well as communication, consumer, computing and
industrial areas. The whole product family is produced in Dark Green packages, which are
free of halogens and antimony oxides and complies with the classification UL94V-0 and
Restriction of Hazardous Substances (RoHS) standards regarding non-flammability.
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2.2.1 Reduction of the on-state resistance to ultra low values
The saturation voltage can be separated into ohmic losses and losses produced by
recombination and injection processes. Ohmic losses are the biggest contributor to the
saturation voltage of a bipolar transistor. This includes the resistance of the
semiconductor substrate, the design of the chip, the resistances introduced by bonding,
and the package technology.
metall 2
passivation
isolation
metall 1
emitterdoping
basedoping
epitaxial
layer
substrate
006aac623
Fig 5.
Principal architecture of a BISS-4 transistor
In order to reduce the losses of the semiconductor material, low-ohmic substrates doped
with phosphorus are often used. A very homogenous current distribution in the chip and a
low resistance in the chip front-side metallization are key factors necessary to achieve a
low VCEsat value.
The homogenous current distribution is achieved by the mesh-design (see Figure 1 to 4)
which divides the transistor into a cell structure. A patented double-layer front-side
metallization minimizes the resistance of the emitter paths. Figure 5 shows the principal
architecture of a fourth generation BISS transistor.
Figure 6 shows the reduction of RCEsat compared to a conventional low VCEsat transistor in
an SOT23 package. It also shows the contribution of changes in assembly, front
metallization, active area, and substrate material.
006aac624
100
RCEsat
(mΩ)
80
(1)
–60 %
60
(2)
40
(3)
(1)
(2)
20
(4)
(3)
(4)
0
conventional low-voltage
transistor in SOT23
BISS 4th generation in SOT23
The changes for the substrate and the front metallization result in the biggest decrease of RCEsat.
Fig 6.
AN11045
Application note
Compared reduction of collector-emitter saturation resistance
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Figure 7 shows the saturation voltage as a function of collector current for a
general-purpose transistor such as a BC847 compared to a BISS transistor of the
previous generation and to a BISS-4 transistor (PBSS4021NT). The package type is
SOT23.
The saturation voltage for a collector current of 1 A is highlighted. For the new type a
saturation voltage of only 37 mV is measured, which is more than a factor two compared
to the older generation.
006aac625
1.2
VCE
(V)
0.8
(1)
(2)
0.4
84 mV
(3)
37 mV
0.0
10–1
1
10
IC (A)
(1) General-purpose transistor
(2) Previous low VCEsat transistor
(3) 4th generation low VCEsat transistor
Fig 7.
Collector-emitter voltage as a function of collector current; typical values
2.2.2 Reduction of switching and storage times
The target of the design of the second branch of the BISS-4 family was to achieve short
switching and storage times in addition to a small saturation voltage. The diffusion
capacities play the major role for the switching speed. For a transistor in saturation mode,
the base voltage is higher than the collector potential. Parasitic clamping diodes as
depicted in Figure 9 help to reduce the storage time (ts) significantly.
E
IB
B
ID
IC
C
006aac626
Fig 8.
Principal cross section of a BISS-4 transistor
AN11045
Application note
006aac627
Fig 9.
Equivalent circuit with inherent clamping
diode reducing the switching times
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Table 1 shows a comparison between the two branches of the 4th generation of BISS
transistors regarding the storage time and the rise time.
The PBSS4021NT is optimized for an ultra low VCEsat, the PBSS4032NT is designed for
an optimized switching performance. The rise time of the PBSS4032NT is reduced by a
factor three and the storage time is significantly shorter as well.
Table 1.
Comparison of the storage times between the two branches of transistors from
the 4th generation BISS
Transistor version
Type number
storage time (ts)
rise time (tr)
BISS-4, switching-optimized
PBSS4032NT
135 ns
20 ns
BISS-4, optimized for lowest VCEsat
PBSS4021NT
340 ns
60 ns
3. Application examples with BISS transistors
3.1 Load switch application
A typical application for low VCEsat transistors is a so-called load switch (see Figure 10).
The most commonly used architecture for this circuit is the combination of a high-side
switch (T1) and a control transistor (T2). In this approach the loads are constantly
connected to ground and the positive supply can be turned on and off.
VI
T1
VO
Rload
R1
R2
R3
T2
R4
006aac628
Fig 10. Load switch circuit consisting of a BISS in the load path (T1) and a
general-purpose control transistor (T2)
The realization of a load switch with bipolar transistors has some major advantages.
Reverse currents from the output side back to the input are blocked as an inherent feature
of a BJT. This function is required if the load switch is used as a path element in a charger
application. A battery connected to the output must not feed back current into a connected
input power supply which is switched off. If the load transistor is realized with a P-channel
MOSFET, the body diode would conduct a reverse current. To avoid this, an extra diode in
the load current path needs to be implemented. Because the forward voltage of the diode
needs to be added to the RDSon losses of the FET, the efficiency of such a load switch
application becomes rather low.
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A further advantage of the solution with bipolar transistors is the robustness with respect
to ESD.
Moreover a bipolar transistor requires a small control voltage only, because the forward
voltage of the base-emitter diode is about 0.7 V without a large spread. The gate-source
threshold of a MOSFET has a rather large spread. Therefore a bigger control voltage is
required in practice. If small voltages shall be switched with a P-channel MOSFET in the
load path, a simple circuit approach like depicted in Figure 10 cannot be used anymore
and a BISS transistor is a good option.
The NXP BISS transistors provide a high and constant current amplification. A current
gain (hFE) of about 400 is typical for the BISS transistor family. Thus the control losses are
small compared to a conventional BJT. The control losses for the load path are equal to
IC(T2)  VI. In many applications where MOSFETs have been used, the
BISS-transistor-based solution can be considered.
3.2 Voltage stabilizer
Due to the high and constant current amplification, BISS transistors are a better choice
than general-purpose bipolar transistors for many applications where the device is not
driven in saturation mode.
As an example, Figure 11 shows a simple voltage stabilizer. The active part of the circuit is
an NPN transistor. Its base is connected to the input voltage via R1 and a Zener diode
connected to ground. The output voltage VO follows the equation: VO = VZ  VBE (VZ is the
Zener voltage).
An important key parameter for a voltage stabilizer is the voltage headroom required to
come to the nominal output voltage for a defined output current, this is the so-called
dropout voltage.
VI
VO
T1
R2
5.5 Ω
R1
220 Ω
D1
BZX84C5V6
006aac629
Fig 11. Voltage stabilizer
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Figure 12 shows the output voltage of the circuit versus the input voltage with a load
resistor of 10 . This means that about 0.5 A are driven through the load.
006aac630
5.0
VO
(V)
(1)
4.2
(2)
3.4
2.6
40
50
60
70
VI (V)
(1) NXP BISS transistor PBSS4021PZ
(2) Conventional transistor in SOT223 from a competitor X
Fig 12. Output voltage as a function of input voltage for a voltage stabilizer as depicted in
Figure 11
Due to the high current amplification factor of the BISS transistor, the circuit starts to work
in order to stabilize the output voltage from about 5.8 V onwards. As a result of the low
saturation voltage, a low dropout voltage can be achieved. The general-purpose transistor
requires 0.6 V more. This means that the minimum dropout voltage of the
BISS-transistor-based solution is significantly lower. The base-emitter voltage VBE of the
general-purpose transistor is constantly higher, even if a high input voltage is applied.
The power efficiency of the solution with the NXP BISS transistor is significantly higher.
A lower input voltage can be applied and a lower base current is needed for a desired
output current. The energy efficiency of the solution based on a BISS transistor is much
higher.
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Figure 13 shows a more precise voltage stabilizer circuit. The simple Zener diode is
replaced by a TL431 shunt regulator. If the reference voltage at R2 tends to fall below
2.495 V, the device increases its cathode to anode resistance. As a consequence T1 gets
a higher base current via R1, increasing the output voltage and thus the exact reference
voltage is maintained. The output voltage can be calculated according to the formula:
V O =  1 + R3  R2   2,495 V
The circuit example is designed for an output voltage of 5 V. A load current of 1 A is
simulated. An input voltage of 6.2 V is high enough as headroom for the stabilizer.
T1
PBSS4021NZ
R1
R2
4.7 kΩ
220 Ω
V1
6.2 V
R5
5Ω
IC1
TL431
R3
4.7 kΩ
006aac631
Fig 13. Precision voltage stabilizer with a TL431 shunt regulator and a BISS transistor as
power stage
3.3 DC-to-DC converter
Another suitable application for low VCEsat transistors and specifically the product branch
optimized for high-speed switching is the area of DC-to-DC conversion.
VO
DC-to-DC
controller
R1
T1
PBSS4032PD
D1
PMEG3020ER
L1
VI
C1
R2
006aac632
Fig 14. DC-to-DC down-converter with BISS-4 PNP switching transistor
Figure 14 shows an example for a DC-to-DC down-converter.
While the BISS transistor T1 is switched on, the current through the inductor L1
increases. The capacitor C1 is charged and a current flows through the load resistor R2.
When the transistor is switched off, the current through L1 continues to flow, but through
the Schottky diode D1. The current decreases over time. As a result, the current through
L1 shows a triangle shape if we assume a load condition where the converter runs in the
so-called continuous mode. This means that the current through the inductor never goes
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down to zero. The ripple of the output voltage is reduced by the capacitor C1 to a desired
level. If the switching frequency is increased, smaller inductors and capacitors can be
used. On the other hand more switching losses occur in T1.
The efficiency of the circuit is mainly determined by the RCEsat of T1 and the switching
losses at the transition times of T1. The diode D1 produces forward losses (VF  Iload) for
the time that T1 is switched off and reserve losses (VI  IR) when T1 is switched on. If the
diode is run at a high temperature, the reverse losses increase while the forward voltage
is decreasing.
Furthermore the control energy for T1 has to be taken into account (IB  VBE) as well as
ohmic losses in L1 and C1.
The output voltage for the continuous mode can be calculated rather easily as VO =   VI.
 is the duty cycle of the switching of T1.
The high and constant current gain, the low saturation voltage and the good switching
performance of NXP BISS-4 transistors like the PBSS4032PD allow the use of a bipolar
transistor for the described circuit of medium-power DC-to-DC converter instead of a
P-channel MOSFET. The BISS transistor proposed in the example is optimized for
minimized switching times. It is a product out of the high-speed switching branch from the
fourth-generation BISS transistor family (see Section 2.2.2). The storage and switching
times are much reduced compared to types optimized for an ultra low VCEsat.
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3.4 Overvoltage protection
This section is about an application that can protect a load circuit against an overvoltage
which might occur due to a defective or an unsuitable power supply.
Figure 15 shows the circuit diagram. The input voltage VI is connected via the resistor
divider R2 and R3 to the reference input of a TL431 shunt regulator IC1. If the voltage at
the reference input is below 2.495 V, there is a very low current through R1 and T2 does
not conduct. Therefore T1 is switched on via the bias resistor R5 and the input voltage is
fed to the load circuit without large voltage losses (VO = VI  VCEsat).
If the input voltage rises to a value where the voltage at the reference pin of IC1 exceeds
2.495 V, a current starts to flow through R1, T2 is switched on and T1 is switched off. The
load circuit at the output is protected against an overvoltage. If V I   1 + R3  R2   2,495 ,
the protection is getting active. This means that the load is disconnected from the supply
voltage.
T1
PBSS4021PZ
R1
220 Ω
R4
220 Ω
R2
4.7 kΩ
T2
PMBT4403
Rload
100 Ω
IC1
TL431
R3
4.7 kΩ
R5
470 Ω
006aac633
Fig 15. Overvoltage protection with a BISS transistor in the load path
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The scope trace in Figure 16 shows the output voltage of the circuit at the load resistor
Rload. A triangle-shaped waveform is applied at the input of the circuit. The output voltage
follows the input until V I   1 + R3  R2   2,495 becomes true. In this case the output
voltage is switched off and the connected circuit cannot be destroyed by an overvoltage
supplied from the input.
006aac634
6
VO
(V)
4
2
0
–2
0.0
0.2
0.4
0.6
0.8
1.0
t (s)
Fig 16. Output voltage at load resistance
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3.5 Charger application
Low VCEsat transistors can be found in many charger applications, such as chargers for
mobile phone, navigation systems and other battery-driven medium-power applications.
A block diagram of such a charging application is shown in Figure 17.
VCHARGE
VBATT
Low VCEsat PNP transistor
VBATT
TBATT
Power management unit
Lithium-ion
battery
ISENSE
R1
GND
006aac635
VBATT: battery voltage
VCHARGE: charge voltage
GND: ground
TBATT: battery temperature
ISENSE: current sense
Fig 17. Charger application using a low VCEsat transistor as path element
The advantage of this solution is the inherent reverse blocking of a bipolar transistor. In
FET solutions, an extra diode needs to be added or two FETs in a back-to-back
configuration need to be used. Depending on the concept of the power management unit,
the charging is controlled in a linear or switched mode.
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4. Higher performance in smaller packages
4.1 General-purpose transistors versus low VCEsat transistors
A comparison of a general-purpose transistor like a BC817-40 versus a state-of-the-art
low VCEsat transistor in mesh-emitter technology like the PBSS4240T in depicted in
Table 2. It shows the large achievements in performance for the new design.
With the reduced saturation voltage of the BISS transistor the collector-emitter losses
IC  VCEsat are significantly smaller (factor 7 for the maximum values at collector current
IC = 0.5 A in the example from Table 2). For a defined maximum junction temperature, the
BISS can be used for higher currents. Smaller energy losses and a lower junction
temperature can be achieved if a general-purpose transistor is replaced by a BISS
transistor in an application. As a result, BISS transistors can replace general-purpose
transistors in much bigger packages.
A further advantage is the high gain amplification of the low VCEsat transistors. In addition
the current gain hFE remains stable for high collector currents.
Table 2.
Comparison of a general-purpose transistor with a BISS transistor, both in SOT23
Type number
Collector current Collector-emitter Total power
IC(max)
voltage VCEO(max) dissipation Ptot
Collector-emitter saturation Current gain
voltage VCEsat(max)
hFE(min)
IC = 0.5 A;
IB = 0.05 A
IC = 2 A;
IB = 0.2 A
IC = 0.5 A
BC817-40
0.5 A
45 V
250 mW
700 mV
-
40
PBSS4240T
2.0 A
40 V
300 mW
320 mV
320 mV
300
Many applications do not require high collector-emitter voltages and types like the
PBSS4021NT with a maximum VCEO of 20 V can be used. Table 3 compares a
BCP54 medium-power general-purpose transistor in SOT223 with a PBSS4021NT BISS
transistor in SOT23. The maximum saturation voltage of the PBSS4021NT is 17 % of the
value for the BCP54 although the base current is five times smaller for the BISS transistor.
The power capability of the SOT223 package is about a factor of 3.5 higher than for the
SOT23. This factor is smaller than the improvement factor for the saturation voltage. This
shows that the much smaller BISS transistor can easily replace a general-purpose
transistor in a much bigger package if it is applied in a switching application.
Furthermore the drive current requirements for the driving circuit are very much reduced
for a BISS transistor approach. There is a factor 15 for the minimum gain amplification
between the two types compared in Table 3.
Table 3.
Comparison of a general-purpose transistor (BCP54 in SOT223) with a BISS transistor (PBSS4021NT in
SOT23)
Type number
BCP54
PBSS4021NT
AN11045
Application note
mounting
area
46 mm2
8.2
mm2
Collector
current
IC(max)
Collector-emitter Total power
voltage VCEO(max) dissipation
Ptot
Collector-emitter
saturation voltage
VCEsat(max)
Current gain
hFE(min)
IC = 0.5 A
IC = 0.5 A
1A
45 V
640 mW
500 mV (at IB = 50 mA)
40
4.3 A
20 V
390 mW
20 mV (at IB = 25 mA)
300
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4.2 Supported packages for NXP BISS transistors
NXP BISS transistors are offered in a significant variety of SMD packages: SOT223,
SOT89, SOT457, SOT23, SOT323, SOT363, SOT416, SOT666, and SOT883. In addition
to these well-known gull wing packages, a DFN2020-3 (SOT1061) 2 mm  2 mm Quad
Flat No-leads (QFN) package is available. This package has a thermal performance which
is close to a SOT89, however the mounting area is much smaller. Table 4 compares two
30 V BISS transistors, the PBSS4630PA in DFN2020-3 (SOT1061) and the PBSS4032NX
in SOT89. The factor between the mounting areas is about a quarter, which means that
the DFN2020-3 (SOT1061) package enables a large Printed-Circuit Board (PCB) area
saving for designs with space constraints.
Table 4.
Comparison of two low VCEsat transistors: PMSS4630PA in DFN2020-3 and PBSS4032NX in SOT89
Type number
PBSS4630PA
mounting
area
4.8
mm2
PBSS4032NX 19.9
[1]
mm2
Collector
current
IC(max)
Collector-emitter Total power
voltage VCEO(max) dissipation
Ptot [1]
Collector-emitter
saturation voltage
VCEsat(max)
Current gain
hFE(min)
IC = 2 A; IB = 0.4 A
IC = 2 A
6A
30 V
500 mW
185 mV
260
4.7 A
30 V
600 mW
250 mV
250
Device mounted on an FR4 PCB, single-layer, standard footprint.
NXP develops an increasing portfolio of low VCEsat transistors in DFN packages. Table 5
and 6 give an overview of available BISS transistors in leadless packages.
Table 5.
NPN low VCEsat BISS transistors in leadless packages
Type number
Package
Collector-emitter
voltage VCEO(max)
Collector-emitter saturation
voltage VCEsat
Collector current
IC(max)
IC = 0.5 A; IB = 0.5 A
PBSS4612PA
DFN2020-3
12 V
20 mV
6.0 A
PBSS4620PA
DFN2020-3
20 V
20 mV
6.0 A
PBSS4330PA
DFN2020-3
30 V
40 mV
3.0 A
PBSS4630PA
DFN2020-3
30 V
21 mV
6.0 A
PBSS4560PA
DFN2020-3
60 V
22 mV
6.0 A
PBSS4580PA
DFN2020-3
80 V
25 mV
5.6 A
PBSS8510PA
DFN2020-3
100 V
30 mV
5.2 A
PBSS2515M
DFN1006-3
15 V
250 mV (max)
0.5 A
PBSS2515MB
DFN1006B-3
15 V
250 mV (max)
0.5 A
PBSS2540M
DFN1006-3
40 V
200 mV
0.5 A
PBSS2540MB
DFN1006B-3
40 V
200 mV
0.5 A
AN11045
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Table 6.
PNP low VCEsat BISS transistors in leadless packages
Type number
Package
Collector-emitter
voltage VCEO(max)
Collector-emitter saturation
voltage VCEsat
Collector current
IC(max)
PBSS5612PA
DFN2020-3
12 V
20 mV
6.0 A
PBSS5620PA
DFN2020-3
20 V
25 mV
6.0 A
PBSS5330PA
DFN2020-3
30 V
45 mV
3.0 A
PBSS5630PA
DFN2020-3
30 V
25 mV
6.0 A
PBSS5560PA
DFN2020-3
60 V
35 mV
5.0 A
PBSS5580PA
DFN2020-3
80 V
40 mV
4.0 A
PBSS9410PA
DFN2020-3
100 V
45 mV
2.7 A
PBSS3515M
DFN1006-3
15 V
150 mV
0.5 A
PBSS3515MB
DFN1006B-3
15 V
150 mV
0.5 A
PBSS3540M
DFN1006-3
40 V
220 mV
0.5 A
PBSS3540MB
DFN1006B-3
40 V
220 mV
0.5 A
IC = 0.5 A; IB = 0.5 A
5. Summary
Thanks to their outstanding low saturation voltage combined with a high current
amplification rather constant for high collector currents, NXP low VCEsat transistors can
improve the energy efficiency in many application areas. With the fourth generation of
BISS transistors NXP offers the best-in-class products. Due to their superior performance,
low VCEsat transistors can replace standard transistors in bigger packages allowing more
compact designs on smaller PCBs.
Two branches of low VCEsat transistors are provided. The first is optimized for ultra low
saturation voltages, and the second branch is optimized for high-speed switching. The
products are available in a significant range of SMD packages from SOT223 down to the
small SOT883. The devices are offered as single and double transistors, as
Resistor-Equipped Transistors (RETs) and as integrated load switches.
A wide field of application can be supported in consumer, automotive, computing and
industrial areas. BISS transistors are often a better choice than comparable MOSFETs
because they provide reverse blocking and high ESD robustness. The losses in the
collector-emitter path are comparable to the RDSon losses of MOSFETs. Due to the high
current amplification, the energy required for the control could be significantly decreased.
AN11045
Application note
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© NXP B.V. 2013. All rights reserved.
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6. Legal information
6.1
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.
6.2
Disclaimers
Limited warranty and liability — 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. NXP Semiconductors takes no
responsibility for the content in this document if provided by an information
source outside of NXP Semiconductors.
In no event shall NXP Semiconductors be liable for any indirect, incidental,
punitive, special or consequential damages (including - without limitation - lost
profits, lost savings, business interruption, costs related to the removal or
replacement of any products or rework charges) whether or not such
damages are based on tort (including negligence), warranty, breach of
contract or any other legal theory.
Notwithstanding any damages that customer might incur for any reason
whatsoever, NXP Semiconductors’ aggregate and cumulative liability towards
customer for the products described herein shall be limited in accordance
with the Terms and conditions of commercial sale of NXP Semiconductors.
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 life support, life-critical or
safety-critical systems or equipment, nor in applications where failure or
malfunction of an NXP Semiconductors product can reasonably be expected
to result in personal injury, death or severe property or environmental
damage. NXP Semiconductors and its suppliers accept 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.
AN11045
Application note
Customers are responsible for the design and operation of their applications
and products using NXP Semiconductors products, and NXP Semiconductors
accepts no liability for any assistance with applications or customer product
design. It is customer’s sole responsibility to determine whether the NXP
Semiconductors product is suitable and fit for the customer’s applications and
products planned, as well as for the planned application and use of
customer’s third party customer(s). Customers should provide appropriate
design and operating safeguards to minimize the risks associated with their
applications and products.
NXP Semiconductors does not accept any liability related to any default,
damage, costs or problem which is based on any weakness or default in the
customer’s applications or products, or the application or use by customer’s
third party customer(s). Customer is responsible for doing all necessary
testing for the customer’s applications and products using NXP
Semiconductors products in order to avoid a default of the applications and
the products or of the application or use by customer’s third party
customer(s). NXP does not accept any liability in this respect.
Export control — This document as well as the item(s) described herein
may be subject to export control regulations. Export might require a prior
authorization from competent authorities.
Evaluation products — This product is provided on an “as is” and “with all
faults” basis for evaluation purposes only. NXP Semiconductors, its affiliates
and their suppliers expressly disclaim all warranties, whether express, implied
or statutory, including but not limited to the implied warranties of
non-infringement, merchantability and fitness for a particular purpose. The
entire risk as to the quality, or arising out of the use or performance, of this
product remains with customer.
In no event shall NXP Semiconductors, its affiliates or their suppliers be liable
to customer for any special, indirect, consequential, punitive or incidental
damages (including without limitation damages for loss of business, business
interruption, loss of use, loss of data or information, and the like) arising out
the use of or inability to use the product, whether or not based on tort
(including negligence), strict liability, breach of contract, breach of warranty or
any other theory, even if advised of the possibility of such damages.
Notwithstanding any damages that customer might incur for any reason
whatsoever (including without limitation, all damages referenced above and
all direct or general damages), the entire liability of NXP Semiconductors, its
affiliates and their suppliers and customer’s exclusive remedy for all of the
foregoing shall be limited to actual damages incurred by customer based on
reasonable reliance up to the greater of the amount actually paid by customer
for the product or five dollars (US$5.00). The foregoing limitations, exclusions
and disclaimers shall apply to the maximum extent permitted by applicable
law, even if any remedy fails of its essential purpose.
6.3
Trademarks
Notice: All referenced brands, product names, service names and trademarks
are the property of their respective owners.
All information provided in this document is subject to legal disclaimers.
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7. Contents
1
2
2.1
2.2
2.2.1
2.2.2
3
3.1
3.2
3.3
3.4
3.5
4
4.1
4.2
5
6
6.1
6.2
6.3
7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Higher performance for low VCEsat BISS
transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Technological background of low VCEsat
transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
BISS-4: a milestone in the development of
medium-power bipolar transistors. . . . . . . . . . . 5
Reduction of the on-state resistance to ultra low
values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Reduction of switching and storage times . . . . 7
Application examples with BISS transistors. . 8
Load switch application . . . . . . . . . . . . . . . . . . 8
Voltage stabilizer. . . . . . . . . . . . . . . . . . . . . . . . 9
DC-to-DC converter . . . . . . . . . . . . . . . . . . . . 11
Overvoltage protection . . . . . . . . . . . . . . . . . . 13
Charger application . . . . . . . . . . . . . . . . . . . . 15
Higher performance in smaller packages . . . 16
General-purpose transistors versus low VCEsat
transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Supported packages for NXP BISS transistors 17
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Legal information. . . . . . . . . . . . . . . . . . . . . . . 19
Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Disclaimers . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Trademarks. . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Please be aware that important notices concerning this document and the product(s)
described herein, have been included in section ‘Legal information’.
© NXP B.V. 2013.
All rights reserved.
For more information, please visit: http://www.nxp.com
For sales office addresses, please send an email to: [email protected]
Date of release: 28 February 2013
Document identifier: AN11045
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