AN21

Application Note 21
Issue 2 January 1996
Bipolar Transistor Considerations for Battery
Powered Equipment
Leading to Efficiency and Competitive Advantages in Portable
Systems
Neil Chadderton
Introduction
The last few years has witnessed an
increasing trend towards portability, this no
doubt being due to a waiting market, and the
advances in the enabling technology within
the digital domain. This in turn has produced
impetus to the advancement of the
analogue technologies, as the customer
requirements dictate a move to integrated,
lower cost, energy efficient products. These
new technologies include higher capacity
battery systems and a re-assessment of
power management techniques. The new
philosophy includes careful charge control
to ensure maximum battery capacity and
lifetime, and consideration of voltage and
current ratings - leading to the design and
characterisation of components specific to
the application.
It is easy to assume that within say, a
laptop computer or a mobile phone, that
th e c i r c u i t bo a r d s w i l l b e w h ol l y
populated with digital ICs, with little or
no analogue circuitry. This is in fact far
from the truth; as the control systems
tend to incorporate more features, and
microprocessors and microcontrollers
move to higher speeds and lower
operating voltages, the demands placed
on the system power supplies, battery
charge schemes, and circuit block power
switches become more exacting.
Portability implies smaller and lighter
components, which is usually
considered to be in opposition with
higher power requirements. The
analogue sections and consequently the
s w i t c h i ng d e v i c e s us e d for the s e
systems, must then be considered and
chos en c a re fully to m e et product
objectives.
Zetex Semiconductors has developed a
bipola r transistor technology that
enables a range of devices ideally suited
to many of the high current, efficiency
conscious circuit concerns of todays
battery powered and portable products.
This technology, the Matrix Geometry,
was initially introduced to effect small
DC motor drivers for cameras, and has
been greatly enhanced to provide a
range of transistors un-matched by any
other manufacturer. This range includes
a 5A continuous device in the TO-92
style E-Line package; SOT223 rated up to
7A; the SuperSOT SOT23 series which
includes a 3A continuous part; and the
c a p a b i l i t y o f p r o d u c i n g S u p e r -β
transistors,
thereby
allowing
cost-effective replacement of larger
Darlington and MOSFET transistors.
AN21- 1
Application Note 21
Issue 2 January 1996
Bipolar Vs MOSFET
Bipolar technology has perhaps been
somewhat overshadowed in recent
years, particularly since the birth of the
MOSFET. This is to be expected due to
two main reasons. Firstly; each major
new technological advancement brings
a wealth of publicity, promotion and a
vast exposure of new design methods
and circuitry. Unfortunately, this same
PR drive comes at some cost: it is by its
nature very selective, and has led to a
commonly held view that bipolar can
always be replaced with a MOS based
product, particularly when speed, cost
effectiveness and on-state efficiency are
of concern. This view is true only some
of the time. If adopted in too general a
fashion, this approach can lead to
non-optimised products, with the usual
market disadvantages in performance
and cost. There is no single device, or
single technology solution to every
application. The second factor is a
general stagnation of bipolar device
research as semiconductor manufacturers
move to the latest technologies. Zetex
recognises that opti mised bipolar
products offer the best fit design option
in many cases, and has pushed the
technology to higher performance
standards than any of it’s competitors.
This section shows that modern bipolar
technology, can provide a credible
alternative to MOS based designs, and
in many cases is the preferred choice.
This is not to decry the use of MOSFETs,
but rather to demonstrate that each
device technology has it’s advantages
and disadvantages, and that each new
application should be judged
individually, not on a wholesale basis.
The information shown in Table 1
provides a basic technology overview of
important Bipolar and MOSFET
characteristics. To do this, a comparison
has been effected between a Zetex 3rd
generation bipolar product such as the
geometry/process used for the
SuperSOT series, and a typical latest
generation MOSFET device.
1. Bipolar still claims the highest silicon
utilisation of any transistor technology.
This is due to the pattern of current flow
within the geometry. Optimised bipolar
geometries force the majority of the
current flow vertically through the
structure. MOSFETs however, still need
to channel the current initially in a lateral
manner before conducting through the
bulk of the device. This fact allows an
optimised bipolar device to use a
smaller area to exhibit a given level of
on-state loss, or, put another way, a
bipolar device can conduct higher levels
of current for the same area of silicon.
This smaller silicon area leads to smaller
packaging options required to
encapsulate that silicon (which is a main
contributer to the final product cost) and
of course smaller products. Figure 1
illustrates the Zetex pioneered Matrix
geometry on which many of the leading
edge products are based.
Another point worth considering is how
the on-state loss varies with
temperature. While the components of
AN21- 2
Table 1
Performance Feature
Bipolar and
MOSFET
Technology 1. Silicon utilisation
Overview.
2. Drive voltage
3.
Drive power
4.
Speed
5.
ESD sensitivity
6.
Price
pure resistance will increase with
increasing temperature, this may be
compensated for (within a given drive
condition) by decreasing threshold
voltage (for the MOSFET) or increasing
hFE (for the bipolar). MOSFET datasheets
typically show RDS(on) increasing by a
factor of x1.7 to x2 over the operating
temperature range. Bipolar devices,
particularly low voltage variants as
designed for battery powered
applications, show a high degree of
Base
Contacts
Zetex 3rd Generation
Bipolar Transistor
Typical Latest
Generation MOSFET
Excellent
Moderate
<1V (V BE)
<2.7V (V th) to 5V
Moderate (high β)
Very low
Fast
Very fast
Rugged
Sensitive
Moderate
Expensive
VCE(sat) t e m p e r a t u r e c om p e n sa t i o n ,
(please refer to Figure 2).
2. The amount of drive voltage required
to activate, turn-on, enhance etc is an
important characteristic of any
semiconductor device. Different
technologies either address the issue
directly in terms of transconductance,
(Gm, gFS), or by secondary effects, Eg.
current gain.
1.8
Emitter
Region
1.6
Collector
Region
1.4
VCE(sat) - (Volts)
This application note aims to provide a
general overview of this Zetex bipolar
transistor technology with particular
respect to selection criteria, comparison
against competing MOSFET solutions,
and performance advantages for low
voltage applications.
Application Note 21
Issue 2 January 1996
Base
Region
-55°C
+25°C
+100°C
+175°C
IC/IB=200
1.2
1.0
0.8
0.6
0.4
0.2
0
Figure 3
The Matrix Geometry
0.001
0.01
0.1
1
10
IC - Collector Current (Amps)
Distributed base resistance is minimised using a
large matrix of base contact holes. By keeping the
size of these holes small, little emitter area is lost
and so active chip area is maximised.
Figure 2
VCE(sat) vs Ic for ZTX788B, Illustrating
Degree of Temperature Dependence.
AN21- 3
Application Note 21
Issue 2 January 1996
Bipolar Vs MOSFET
Bipolar technology has perhaps been
somewhat overshadowed in recent
years, particularly since the birth of the
MOSFET. This is to be expected due to
two main reasons. Firstly; each major
new technological advancement brings
a wealth of publicity, promotion and a
vast exposure of new design methods
and circuitry. Unfortunately, this same
PR drive comes at some cost: it is by its
nature very selective, and has led to a
commonly held view that bipolar can
always be replaced with a MOS based
product, particularly when speed, cost
effectiveness and on-state efficiency are
of concern. This view is true only some
of the time. If adopted in too general a
fashion, this approach can lead to
non-optimised products, with the usual
market disadvantages in performance
and cost. There is no single device, or
single technology solution to every
application. The second factor is a
general stagnation of bipolar device
research as semiconductor manufacturers
move to the latest technologies. Zetex
recognises that opti mised bipolar
products offer the best fit design option
in many cases, and has pushed the
technology to higher performance
standards than any of it’s competitors.
This section shows that modern bipolar
technology, can provide a credible
alternative to MOS based designs, and
in many cases is the preferred choice.
This is not to decry the use of MOSFETs,
but rather to demonstrate that each
device technology has it’s advantages
and disadvantages, and that each new
application should be judged
individually, not on a wholesale basis.
The information shown in Table 1
provides a basic technology overview of
important Bipolar and MOSFET
characteristics. To do this, a comparison
has been effected between a Zetex 3rd
generation bipolar product such as the
geometry/process used for the
SuperSOT series, and a typical latest
generation MOSFET device.
1. Bipolar still claims the highest silicon
utilisation of any transistor technology.
This is due to the pattern of current flow
within the geometry. Optimised bipolar
geometries force the majority of the
current flow vertically through the
structure. MOSFETs however, still need
to channel the current initially in a lateral
manner before conducting through the
bulk of the device. This fact allows an
optimised bipolar device to use a
smaller area to exhibit a given level of
on-state loss, or, put another way, a
bipolar device can conduct higher levels
of current for the same area of silicon.
This smaller silicon area leads to smaller
packaging options required to
encapsulate that silicon (which is a main
contributer to the final product cost) and
of course smaller products. Figure 1
illustrates the Zetex pioneered Matrix
geometry on which many of the leading
edge products are based.
Another point worth considering is how
the on-state loss varies with
temperature. While the components of
AN21- 2
Table 1
Performance Feature
Bipolar and
MOSFET
Technology 1. Silicon utilisation
Overview.
2. Drive voltage
3.
Drive power
4.
Speed
5.
ESD sensitivity
6.
Price
pure resistance will increase with
increasing temperature, this may be
compensated for (within a given drive
condition) by decreasing threshold
voltage (for the MOSFET) or increasing
hFE (for the bipolar). MOSFET datasheets
typically show RDS(on) increasing by a
factor of x1.7 to x2 over the operating
temperature range. Bipolar devices,
particularly low voltage variants as
designed for battery powered
applications, show a high degree of
Base
Contacts
Zetex 3rd Generation
Bipolar Transistor
Typical Latest
Generation MOSFET
Excellent
Moderate
<1V (V BE)
<2.7V (V th) to 5V
Moderate (high β)
Very low
Fast
Very fast
Rugged
Sensitive
Moderate
Expensive
VCE(sat) t e m p e r a t u r e c om p e n sa t i o n ,
(please refer to Figure 2).
2. The amount of drive voltage required
to activate, turn-on, enhance etc is an
important characteristic of any
semiconductor device. Different
technologies either address the issue
directly in terms of transconductance,
(Gm, gFS), or by secondary effects, Eg.
current gain.
1.8
Emitter
Region
1.6
Collector
Region
1.4
VCE(sat) - (Volts)
This application note aims to provide a
general overview of this Zetex bipolar
transistor technology with particular
respect to selection criteria, comparison
against competing MOSFET solutions,
and performance advantages for low
voltage applications.
Application Note 21
Issue 2 January 1996
Base
Region
-55°C
+25°C
+100°C
+175°C
IC/IB=200
1.2
1.0
0.8
0.6
0.4
0.2
0
Figure 3
The Matrix Geometry
0.001
0.01
0.1
1
10
IC - Collector Current (Amps)
Distributed base resistance is minimised using a
large matrix of base contact holes. By keeping the
size of these holes small, little emitter area is lost
and so active chip area is maximised.
Figure 2
VCE(sat) vs Ic for ZTX788B, Illustrating
Degree of Temperature Dependence.
AN21- 3
Application Note 21
Issue 2 January 1996
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0.001
0.01
0.1
1
10 20
IC - Collector Current (Amps)
VBE(sat) v IC
Figure 3
VBE(sat) or “Required Turn-on Voltage" for
ZTX948.
These Super-β transistors possess
typical mid-band hFE values around 450
to 800 (dependent on device), which
allows direct logic mA rated outputs to
control single transistors which switch
many amperes.
4. T h e switching speed capability is
perhaps more straightforward MOSFETs are operated routinely from
10s to 100s of kHz, and even to several
MHz, although care must be taken with
appropriate gate drive circuitry to ensure
a high current charge/discharge buffer for
the gate+Miller capacitance. Optimised
bipolar devices however can still compete
easily up to 100kHz (around x2 the
benchmark figure adopted for standard
bipolar), and with careful attention to base
charge control much higher.
5. ESD is still an issue with some
ass e mbly contra ctors, though the
compliance to safe handling standards,
a n d i n v e s t m e n t i n s ta t i c s a f e
environments will reduce this concern.
AN21- 4
6. Price. As MOSFETs require more
silicon area than bipolar parts for a given
current capability, and MOSFET
production processes demand state of
the art alignment and etching, as well as
more mask stages than bipolar, the
difference in cost of manufacture and
therefore the selling price, can be very
significant.
7. The reverse blocking capability of a
bipolar transistor depends on the state
of the base terminal. If this is left open
circuit/high impedance, as could be the
case with a PNP in high side switch, then
the BVEBO parameter determines the
reverse blocking voltage. MOSFETs
cannot reverse block due to the inherent
drain-source body diode. For some
applications where reverse blocking is
essential, MOSFETs can be configured
as back to back pairs, such that each
MOSFET blocks the body diode of it’s
partner. This does however double the
on-resistance seen by the circuit. Figure
4 shows the typical BVECO characteristic
of a representative Super-β transistor.
8. Bipolar transistors can sometimes offer
the useful feature of inverse gain or hFC.
This is particularly the case for the lower
voltage variants, where the inverse gain
can peak at between 33 to 50% of the peak
forward gain. This is because the relatively
highly doped collector region can also
function well as an “emitter”. For the
Super-β parts this presents a peak inverse
gain in the region of 100 to 300 typically.
This feature can be useful for instance in
positive line switching networks, where
the selection of s upply lines may
effectively reverse the collector-emitter
bias seen by the pass transistor. Another
application benefit of importance is the
possibility of conducting negative
tr a n s ie n t s , a s ca u s e d b y ex t ernal
influences on the supply rail or inductive
loads. This feature can be used to
advantage in some circuits by allowing the
omission of the collector-emitter diode
that would otherwise be required, to
prevent damage to the transistors
emitter-base junction. Figure 5 shows the
inverse gain characteristic for low
collector currents, in the saturation region
for the FMMT717 PNP SOT23 transistor.
200
500
Ic-Collector Current (mA)
3. T h e drive power r e q u i r e d b y a
s w i t c h i n g d e v i c e i s a n i m p o r t a nt
concern, and must be considered to
appreciate the full system’s power loss.
At DC and low frequencies, the
MOSFET’s drive power requirement is
essentially zero, while the bipolar
transistor requires base current, leading
to losses in the base (VBE(sat) x IB) and (if
required) the base drive resistor ((Vlogic
-VBE)2)/RB) . T h e s e l o s s e s c a n b e
minimised however, by employing
devices with very high current gain.
IC/IB=10
Ic-Collector Current (uA)
F o r t he b i p ol a r d e v i ce , t h e u s u a l
enabling parameter of concern is current
gain, hFE or β. However to assist this
comparison exercise - in terms of drive
voltage the bipolar transistor of course
o n l y r e q u i r e s a VBE t o p r o m o t e
collector-emitter conduction. For low
currents this VBE can be less than 400mV,
perhaps rising to 1V or so at moderate to
high currents, (please refer to Figure 3),
thus allowing true logic level operation
from 5V, 3.3V and lower operating
voltage logic families.
-55°C
+25°C
+100°C
+175°C
1.6
VBE(sat) - (Volts)
Due to reducing system operating
voltages, MOSFET vendors have
reduced the threshold voltage, and
the re for e the gate-s ource vol tage
r e q u i r e d f o r e n h a n c e m e n t o f th e
MOSFET channel. Even so, for full
enhancement, to achieve datasheet and
quoted resistance values, many
standard MOSFETs can still require 10V
or more, while low threshold devices
need 4.5 to 5V. Many systems may not
have this level of voltage drive available,
so it is very important to fully assess the
true level of on-resistance presented to
the circuit, in order to understand the
loss mechanisms.
Application Note 21
Issue 2 January 1996
250
0
0
5
200uA PER STEP
100
0
10
0
Vec-Emitter Collector Voltage (V)
250
500
Vce-Collector Emitter Voltage (mV)
Ic v Vec
Figure 4
Reverse Blocking Capability of Bipolar
Transistors.
Ic v Vce
Figure 5
Inverse Gain Characteristic of FMMT717.
AN21- 5
Application Note 21
Issue 2 January 1996
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0.001
0.01
0.1
1
10 20
IC - Collector Current (Amps)
VBE(sat) v IC
Figure 3
VBE(sat) or “Required Turn-on Voltage" for
ZTX948.
These Super-β transistors possess
typical mid-band hFE values around 450
to 800 (dependent on device), which
allows direct logic mA rated outputs to
control single transistors which switch
many amperes.
4. T h e switching speed capability is
perhaps more straightforward MOSFETs are operated routinely from
10s to 100s of kHz, and even to several
MHz, although care must be taken with
appropriate gate drive circuitry to ensure
a high current charge/discharge buffer for
the gate+Miller capacitance. Optimised
bipolar devices however can still compete
easily up to 100kHz (around x2 the
benchmark figure adopted for standard
bipolar), and with careful attention to base
charge control much higher.
5. ESD is still an issue with some
ass e mbly contra ctors, though the
compliance to safe handling standards,
a n d i n v e s t m e n t i n s ta t i c s a f e
environments will reduce this concern.
AN21- 4
6. Price. As MOSFETs require more
silicon area than bipolar parts for a given
current capability, and MOSFET
production processes demand state of
the art alignment and etching, as well as
more mask stages than bipolar, the
difference in cost of manufacture and
therefore the selling price, can be very
significant.
7. The reverse blocking capability of a
bipolar transistor depends on the state
of the base terminal. If this is left open
circuit/high impedance, as could be the
case with a PNP in high side switch, then
the BVEBO parameter determines the
reverse blocking voltage. MOSFETs
cannot reverse block due to the inherent
drain-source body diode. For some
applications where reverse blocking is
essential, MOSFETs can be configured
as back to back pairs, such that each
MOSFET blocks the body diode of it’s
partner. This does however double the
on-resistance seen by the circuit. Figure
4 shows the typical BVECO characteristic
of a representative Super-β transistor.
8. Bipolar transistors can sometimes offer
the useful feature of inverse gain or hFC.
This is particularly the case for the lower
voltage variants, where the inverse gain
can peak at between 33 to 50% of the peak
forward gain. This is because the relatively
highly doped collector region can also
function well as an “emitter”. For the
Super-β parts this presents a peak inverse
gain in the region of 100 to 300 typically.
This feature can be useful for instance in
positive line switching networks, where
the selection of s upply lines may
effectively reverse the collector-emitter
bias seen by the pass transistor. Another
application benefit of importance is the
possibility of conducting negative
tr a n s ie n t s , a s ca u s e d b y ex t ernal
influences on the supply rail or inductive
loads. This feature can be used to
advantage in some circuits by allowing the
omission of the collector-emitter diode
that would otherwise be required, to
prevent damage to the transistors
emitter-base junction. Figure 5 shows the
inverse gain characteristic for low
collector currents, in the saturation region
for the FMMT717 PNP SOT23 transistor.
200
500
Ic-Collector Current (mA)
3. T h e drive power r e q u i r e d b y a
s w i t c h i n g d e v i c e i s a n i m p o r t a nt
concern, and must be considered to
appreciate the full system’s power loss.
At DC and low frequencies, the
MOSFET’s drive power requirement is
essentially zero, while the bipolar
transistor requires base current, leading
to losses in the base (VBE(sat) x IB) and (if
required) the base drive resistor ((Vlogic
-VBE)2)/RB) . T h e s e l o s s e s c a n b e
minimised however, by employing
devices with very high current gain.
IC/IB=10
Ic-Collector Current (uA)
F o r t he b i p ol a r d e v i ce , t h e u s u a l
enabling parameter of concern is current
gain, hFE or β. However to assist this
comparison exercise - in terms of drive
voltage the bipolar transistor of course
o n l y r e q u i r e s a VBE t o p r o m o t e
collector-emitter conduction. For low
currents this VBE can be less than 400mV,
perhaps rising to 1V or so at moderate to
high currents, (please refer to Figure 3),
thus allowing true logic level operation
from 5V, 3.3V and lower operating
voltage logic families.
-55°C
+25°C
+100°C
+175°C
1.6
VBE(sat) - (Volts)
Due to reducing system operating
voltages, MOSFET vendors have
reduced the threshold voltage, and
the re for e the gate-s ource vol tage
r e q u i r e d f o r e n h a n c e m e n t o f th e
MOSFET channel. Even so, for full
enhancement, to achieve datasheet and
quoted resistance values, many
standard MOSFETs can still require 10V
or more, while low threshold devices
need 4.5 to 5V. Many systems may not
have this level of voltage drive available,
so it is very important to fully assess the
true level of on-resistance presented to
the circuit, in order to understand the
loss mechanisms.
Application Note 21
Issue 2 January 1996
250
0
0
5
200uA PER STEP
100
0
10
0
Vec-Emitter Collector Voltage (V)
250
500
Vce-Collector Emitter Voltage (mV)
Ic v Vec
Figure 4
Reverse Blocking Capability of Bipolar
Transistors.
Ic v Vce
Figure 5
Inverse Gain Characteristic of FMMT717.
AN21- 5
Application Note 21
Issue 2 January 1996
9 and 10. These last two factors are
somewhat of an invention, but serve to
demonstrate that when considered in
ter ms of equiva lent on-resistance
(whether that is RDS(on) for a MOSFET, or
RCE(sat) for a bipolar transistor) and most
importantly cost, the bipolar option can
be very attractive.
Figures 6 and 7 help to illustrate some of
the points raised in 1 and 3 above,
namely the silicon efficiency, on-state
loss, and drive losses. These charts
show the amount of power loss
exhibited by a range of SOT23 and one
SOT89 surface mount transistors as a
function of load current. Figure 6 shows
curves for NPN and N-Channel parts,
and Figure 7 shows curves for PNP and
P-Channel parts. These curves do NOT
represent the minimum loss irrespective
of package - they refer to industry
standard and best-in-class SOT23 and
SOT89 products only. It is noteworthy
that the BCX69 part referenced is
actually a SOT89 packaged transistor.
Application Note 21
Issue 2 January 1996
Key Parameters
The previous section has touched on
some of the circuit parameters useful in
comparing the two technology classes,
when considering products for battery
powered systems. Perhaps the most
useful of these parameters is RCE(sat), this
being the collector-emitter resistance,
and is equivalent (in a datasheet sense)
t o RDS(on); t h e c o m m o n M O S F E T
benchmark parameter. Table 2 shows a
selection of the low voltage variant
Zetex transistors specifically developed
for battery system operation, and
includes RCE(sat) figures for illustration
purposes. As with any datasheet figure,
point measurement values must be used
as guidelines only. For application
specifics, knowledge of the circuit
operating conditions, datasheet test
points and characterisation curves can
usually lead to a credible interpolation.
Device
(Note 1)
Polarity
IC (DC)
ICM
VCE(sat )
(Note 2)
RCE(sat)
hFE
(Note 3)
FMMT617
NPN
3
12
50mV @ 1A
150mV @ 3A
50mΩ
450 typ
FMMT618
NPN
2.5
6
50mV @ 1A
100mV @ 2A
50mΩ
450 typ
FMMT717
PNP
2.5
10
80mV @ 1A
140mV @ 2A
80mΩ
450 typ
FMMT718
PNP
1.5
6
110mV @ 1A
150mV @ 2A
55mΩ
450 typ
ZTX688B
NPN
3
10
50mV @ 1A
250mV @ 3A
50mΩ
750 typ
ZTX788B
PNP
3
8
50mV @ 0.5A
300mV @ 3A
100mΩ
650 typ
ZTX1048A
NPN
4
20
24mV @ 0.5A
48mΩ
450 typ
ZTX869
NPN
5
20
25mV @ 0.5A
180mV @ 5A
50mΩ
450 typ
ZTX949
PNP
4.5
20
40mV @ 0.5A
240mV @ 5A
80mΩ
200 typ
Table 2
Low Voltage transistors for Battery and Portable Systems.
lo
ET
3M
OS
F
SO
T2
n
Ge
(FM
es
es
ss
oss
nL
ctio
u
d
n
Co
Losses
Total Drive
tal
To
100
7)
61
MT
Lo
Typical SOT23
MOSFET Losses
ss
es
600
Power Losses (mW)
200
5t
h
300
lL
os
se
s(
BC
81
8)
400
To
ta
t Losses
3 Mosfe
500
Typical
SOT2
Power Losses (mW)
600
500
400
300
200
100
To
5th
(BSS84)
tal
ge
Lo
ne
ss
ra
e
sB
tio
nS
CX
69
OT
(SO
23
MO
T8
9)
SF
ET
Lo
ss
es
Notes:
1. These represent a selection from some of the transistor families available from Zetex. Eg. the ZTX688B
is a 12V 3A part from the ZTX688B-696B series, similarly the ZTX788B is part of the ZTX788B-795A series.
Please note that surface mount equivalents are available for any ZTX (through-hole) pre-fixed part.
)
17
T7
M
M
es
(F
ss
es
Lo
ss
on
i
o
t
lL
uc
ta
nd
To
Co
Base Losses
0
0.5
1
1.5
2
0
0.5
1.0
1.5
3. These values are guidance only, and are typical mid-band figures. Please refer to the appropriate
datasheet. (Appendix A contains FMMT717 data ).
2.0
Load Current (A)
Load Current (A)
Figure 6
NPN/N-Channel Power Loss vs Load
Current comparison.
es
Drive Loss
Base Losses
0
0
2. These VCE(sat) values are point measurements only, and depend on collector current, base drive level,
and temperature. Please consult the appropriate datasheet for full DC characterisation. The corresponding
values of RCE(sat) are shown for this point measurement, for application specific values consult the
datasheet.
Figure 7
PNP/P-Channel Power Loss vs Load
Current comparison.
AN21- 6
AN21- 7
Application Note 21
Issue 2 January 1996
9 and 10. These last two factors are
somewhat of an invention, but serve to
demonstrate that when considered in
ter ms of equiva lent on-resistance
(whether that is RDS(on) for a MOSFET, or
RCE(sat) for a bipolar transistor) and most
importantly cost, the bipolar option can
be very attractive.
Figures 6 and 7 help to illustrate some of
the points raised in 1 and 3 above,
namely the silicon efficiency, on-state
loss, and drive losses. These charts
show the amount of power loss
exhibited by a range of SOT23 and one
SOT89 surface mount transistors as a
function of load current. Figure 6 shows
curves for NPN and N-Channel parts,
and Figure 7 shows curves for PNP and
P-Channel parts. These curves do NOT
represent the minimum loss irrespective
of package - they refer to industry
standard and best-in-class SOT23 and
SOT89 products only. It is noteworthy
that the BCX69 part referenced is
actually a SOT89 packaged transistor.
Application Note 21
Issue 2 January 1996
Key Parameters
The previous section has touched on
some of the circuit parameters useful in
comparing the two technology classes,
when considering products for battery
powered systems. Perhaps the most
useful of these parameters is RCE(sat), this
being the collector-emitter resistance,
and is equivalent (in a datasheet sense)
t o RDS(on); t h e c o m m o n M O S F E T
benchmark parameter. Table 2 shows a
selection of the low voltage variant
Zetex transistors specifically developed
for battery system operation, and
includes RCE(sat) figures for illustration
purposes. As with any datasheet figure,
point measurement values must be used
as guidelines only. For application
specifics, knowledge of the circuit
operating conditions, datasheet test
points and characterisation curves can
usually lead to a credible interpolation.
Device
(Note 1)
Polarity
IC (DC)
ICM
VCE(sat )
(Note 2)
RCE(sat)
hFE
(Note 3)
FMMT617
NPN
3
12
50mV @ 1A
150mV @ 3A
50mΩ
450 typ
FMMT618
NPN
2.5
6
50mV @ 1A
100mV @ 2A
50mΩ
450 typ
FMMT717
PNP
2.5
10
80mV @ 1A
140mV @ 2A
80mΩ
450 typ
FMMT718
PNP
1.5
6
110mV @ 1A
150mV @ 2A
55mΩ
450 typ
ZTX688B
NPN
3
10
50mV @ 1A
250mV @ 3A
50mΩ
750 typ
ZTX788B
PNP
3
8
50mV @ 0.5A
300mV @ 3A
100mΩ
650 typ
ZTX1048A
NPN
4
20
24mV @ 0.5A
48mΩ
450 typ
ZTX869
NPN
5
20
25mV @ 0.5A
180mV @ 5A
50mΩ
450 typ
ZTX949
PNP
4.5
20
40mV @ 0.5A
240mV @ 5A
80mΩ
200 typ
Table 2
Low Voltage transistors for Battery and Portable Systems.
lo
ET
3M
OS
F
SO
T2
n
Ge
(FM
es
es
ss
oss
nL
ctio
u
d
n
Co
Losses
Total Drive
tal
To
100
7)
61
MT
Lo
Typical SOT23
MOSFET Losses
ss
es
600
Power Losses (mW)
200
5t
h
300
lL
os
se
s(
BC
81
8)
400
To
ta
t Losses
3 Mosfe
500
Typical
SOT2
Power Losses (mW)
600
500
400
300
200
100
To
5th
(BSS84)
tal
ge
Lo
ne
ss
ra
e
sB
tio
nS
CX
69
OT
(SO
23
MO
T8
9)
SF
ET
Lo
ss
es
Notes:
1. These represent a selection from some of the transistor families available from Zetex. Eg. the ZTX688B
is a 12V 3A part from the ZTX688B-696B series, similarly the ZTX788B is part of the ZTX788B-795A series.
Please note that surface mount equivalents are available for any ZTX (through-hole) pre-fixed part.
)
17
T7
M
M
es
(F
ss
es
Lo
ss
on
i
o
t
lL
uc
ta
nd
To
Co
Base Losses
0
0.5
1
1.5
2
0
0.5
1.0
1.5
3. These values are guidance only, and are typical mid-band figures. Please refer to the appropriate
datasheet. (Appendix A contains FMMT717 data ).
2.0
Load Current (A)
Load Current (A)
Figure 6
NPN/N-Channel Power Loss vs Load
Current comparison.
es
Drive Loss
Base Losses
0
0
2. These VCE(sat) values are point measurements only, and depend on collector current, base drive level,
and temperature. Please consult the appropriate datasheet for full DC characterisation. The corresponding
values of RCE(sat) are shown for this point measurement, for application specific values consult the
datasheet.
Figure 7
PNP/P-Channel Power Loss vs Load
Current comparison.
AN21- 6
AN21- 7
Application Note 21
Issue 2 January 1996
The voltage rating parameters also
require some examination. For bipolar
parts the voltage rating most often
quoted is the BVCEO parameter, which is
the collector-emitter breakdown voltage
with the base terminal open-circuit. The
primary breakdown of the epitaxial layer
however is more closely represented by
the BVCBO or BVCES parameters, and for
many circuit topologies it is this rating
that is of most relevance as the base is
never open circuit; being driven actively,
or tied to the appropriate rail by a
resistor. For realistic comparisons with
MOSFET devices, the primary value
given by BVCBO , BVCES, or even BVCEV
should be considered if allowed by the
circuit. This will probably lead to the
selection of a lower voltage rated part
than would otherwise be the case,
leading to a lower VCE(sat) specification,
and hence higher circuit performance.
Please refer to Figure 8.
Table 3 provides a guide to common
bipolar/MOS terminology.
Bipolar
MOSFET
IC (DC)
ID (DC)
ICM
IDM
BVCES
BVDSS
VBE(sat)
VGS
IEBO
IGSS
ICES
IDSS
RCE(sat) = VCE(sat )/IC
hFE
RDS(on) = V DS(on)/ID
gFS
Cibo
Ciss
Cobo
Coss
Table 3
Bipolar/MOSFET Terminology.
Application Note 21
Issue 2 January 1996
Applications
LCD Backlighting
Perhaps the most difficult power supply
to effect within a laptop, and which has
attracted much interest from many
vendors, is the high voltage DC-AC
inverter required by the fluorescent tube
used to provide back/edge lighting for
the LCD display. The tube expects a very
high voltage to initiate conduction,
perhaps 1kV, and several hundred volts
during operation. This supply
compliance must be effected with a very
high degree of efficiency from the
available energy source; - typically a ten
cell NiCd or NiMH battery pack. The
ZTX1048A series of transistors permit
conversion efficiencies of over 90%
prov i di ng s i gnifica nt increas es in
battery life, and therefore less re-charge
cycles. The ZTX1048A and ZTX1049A
devic es have been developed
specifically for the resonant push-pull
(or Royer) inverter used almost
exclusively for this purpose, and Zetex
has already achieved many design-ins in
this application. The ’1048 and ’1049
transistors are also available as an
uncommitted dual device in the space
saving SM-8 package as the ZDT1048
and ZDT1049.
[Note: The SM-8 package is an eight lead
version of the popular SOT223 package
and can thus yield a 50% space saving].
Figure 9 shows a floating lamp CCFL
circuit developed by Linear Technology,
using the LT1182 CCFL/LCD contrast
dual switching regulator, and either a
Zetex datasheets for the very low VCE(sat),
high current transistors include curves
showing how VCE(sat) varies with both
forced gain and temperature, as well as
the more usual hFE profile, VBE(on), VBE(sat)
and safe operating area (SOA) charts.
Appendix A presents an example of the
characterisation available for many of
the battery product targeted bipolar
transistors: in this case the datasheet for
the FMMT717 SOT23 PNP device. This is
a 1 2V, 2.5 A continuous high gain
transistor that has been developed
specifically for use as an high efficiency
positive line switch for DC rail control,
and high current DC-DC converters.
Figure 8
Voltage Breakdown Modes of ZTX849.
1 - BVCBO, 2 - BVCES, 3 - BVCEV, 4 - BVCEO,
5 - BVCE with VBE = 0.5V
Scaling: 10V/div horiz.; 200µA/div vert.
AN21- 8
Figure 9
Floating Tube CCFL Backlight Inverter (Linear Technology) using 2 x FZT849 or the
ZDT1048 SM8 Dual transistor.
AN21- 9
Application Note 21
Issue 2 January 1996
The voltage rating parameters also
require some examination. For bipolar
parts the voltage rating most often
quoted is the BVCEO parameter, which is
the collector-emitter breakdown voltage
with the base terminal open-circuit. The
primary breakdown of the epitaxial layer
however is more closely represented by
the BVCBO or BVCES parameters, and for
many circuit topologies it is this rating
that is of most relevance as the base is
never open circuit; being driven actively,
or tied to the appropriate rail by a
resistor. For realistic comparisons with
MOSFET devices, the primary value
given by BVCBO , BVCES, or even BVCEV
should be considered if allowed by the
circuit. This will probably lead to the
selection of a lower voltage rated part
than would otherwise be the case,
leading to a lower VCE(sat) specification,
and hence higher circuit performance.
Please refer to Figure 8.
Table 3 provides a guide to common
bipolar/MOS terminology.
Bipolar
MOSFET
IC (DC)
ID (DC)
ICM
IDM
BVCES
BVDSS
VBE(sat)
VGS
IEBO
IGSS
ICES
IDSS
RCE(sat) = VCE(sat )/IC
hFE
RDS(on) = V DS(on)/ID
gFS
Cibo
Ciss
Cobo
Coss
Table 3
Bipolar/MOSFET Terminology.
Application Note 21
Issue 2 January 1996
Applications
LCD Backlighting
Perhaps the most difficult power supply
to effect within a laptop, and which has
attracted much interest from many
vendors, is the high voltage DC-AC
inverter required by the fluorescent tube
used to provide back/edge lighting for
the LCD display. The tube expects a very
high voltage to initiate conduction,
perhaps 1kV, and several hundred volts
during operation. This supply
compliance must be effected with a very
high degree of efficiency from the
available energy source; - typically a ten
cell NiCd or NiMH battery pack. The
ZTX1048A series of transistors permit
conversion efficiencies of over 90%
prov i di ng s i gnifica nt increas es in
battery life, and therefore less re-charge
cycles. The ZTX1048A and ZTX1049A
devic es have been developed
specifically for the resonant push-pull
(or Royer) inverter used almost
exclusively for this purpose, and Zetex
has already achieved many design-ins in
this application. The ’1048 and ’1049
transistors are also available as an
uncommitted dual device in the space
saving SM-8 package as the ZDT1048
and ZDT1049.
[Note: The SM-8 package is an eight lead
version of the popular SOT223 package
and can thus yield a 50% space saving].
Figure 9 shows a floating lamp CCFL
circuit developed by Linear Technology,
using the LT1182 CCFL/LCD contrast
dual switching regulator, and either a
Zetex datasheets for the very low VCE(sat),
high current transistors include curves
showing how VCE(sat) varies with both
forced gain and temperature, as well as
the more usual hFE profile, VBE(on), VBE(sat)
and safe operating area (SOA) charts.
Appendix A presents an example of the
characterisation available for many of
the battery product targeted bipolar
transistors: in this case the datasheet for
the FMMT717 SOT23 PNP device. This is
a 1 2V, 2.5 A continuous high gain
transistor that has been developed
specifically for use as an high efficiency
positive line switch for DC rail control,
and high current DC-DC converters.
Figure 8
Voltage Breakdown Modes of ZTX849.
1 - BVCBO, 2 - BVCES, 3 - BVCEV, 4 - BVCEO,
5 - BVCE with VBE = 0.5V
Scaling: 10V/div horiz.; 200µA/div vert.
AN21- 8
Figure 9
Floating Tube CCFL Backlight Inverter (Linear Technology) using 2 x FZT849 or the
ZDT1048 SM8 Dual transistor.
AN21- 9
Application Note 21
Issue 2 January 1996
pair of FZT849s or a ZDT1048 SM-8 dual
transistor to produce a 90% efficient
i n v e r t e r . P l e a s e r e f e r to L i n e a r
Technology application note AN65 Oct
9 5 , “ A F ou r t h G e n e r at i o n o f L C D
Backlight Technology” by Jim Williams.
Power Supply Switching
P o w e r s u p p l y s w i tc h i n g f o r l o a d
m a n a g e m e n t ( s u c h a s p e r i ph e r a l
control, transmit circuit blocks in
handphones, and RAM back-up) should
be considered carefully in terms of the
DC and peak currents required; the
allowable voltage drop across the switch
element (the PCMCIA power switching
specification for example, states a 5%
maximum drop at a 1A output, from the
nominal 5V or 3.3V rail); ease of drive
and cost constraints. The FMMT717 is a
SOT23 PNP transistor that exhibits a
best in class VCE(sat) of 100mV at a pass
current of 1A, equating to a switch
resistance of 100mΩ. This on-state
performance also allows a 2.5A DC
capability, providing a power switch for
PCMCIA (peripherals may demand up to
1.5A peak for say hard disc spin-up),
mobile phone battery chargers, and
battery management systems, that is
reliable and offers the most space and
cost efficient solution. To perform the
same function with a P-Channel MOSFET
would require a much larger die (and
therefore package) and therefore an
increase in price and weight for the user.
Analogue IC vendors manufacture
microprocessor
power
supply
supervisory devices, that monitor the
state of memory supply rails and switch
over the supplies as required. These
devices often require a low loss PNP or
P-Channel part as the pass element, and
this function can usually be effected
with much less cost by a suitable PNP
transistor.
Voltage Regulation
Low drop out regulator controller ICs are
now available that provide the user with
the advantages of a monolithic voltage
reference, and the freedom to specify
the output device rele vant to the
application. These devices usually
require a PNP device to function as the
linear drop element. To allow the system
to operate down to the minimum input
voltage as the battery pack reaches the
end of a discharge cycle, implies that the
transistor must exhibit very low VCE(sat),
preferably with a minimal amount of
base drive drawn from the controller IC.
Device
Package
IC (DC)
PD
VCE(sat)
@Ic /Ib
FMMT717
SOT23
2.5A
625mW
100mV
1A /10mA
ZTX788B
E-Line
3A
1W
190mV
1A /5mA
ZTX949
E-Line
4.5A
1.2W
190mV
3A /60mA
ZBD949
TO126
5A
2W/25W
480mV
5A /50mA
Table 4
PNP Transistors for Low Dropout regulator Designs.
AN21- 10
Application Note 21
Issue 2 January 1996
There are a number of Zetex parts ideally
suited for this application, and Table 4
provides an overview of suitable parts.
Fi gur e 10 s ho w s t wo ty pic al L DO
regulator circuits published by Linear
Technology and MAXIM.
620
5.4 - 7.2V
ZBD949
10µF
20
Drive
OUTPUT
= 5V/4A
F/b
LT1123
10µF
Gnd
Input +3.5V to +5V ZTX749
Base
27
In
On
Blim
Out
MAX687
0.47µF
Output 3.3V at 500mA
Gnd
50µF
PFO
CC 10nF
Gnd
Figure 10
Low Drop Out Regulators - IC + Discrete
Implementation.
DC-DC Converters and Fast Chargers
Battery charge management and fast
charge circ uit topologies using
intelligent charge, voltage inflection,
current, and cell temperature
monitoring, frequently employ a DC-DC
converter to effect an efficient charge
transfer between the available source
and the battery pack. This is usually a
step down or Buck converter which
d i c t a t e s a fa i r l y h i g h o p e r a t i n g
f r e q u e n c y (t o m e e t i n d uc t or s i z e
constraints), and is also subject to very
tight cos t c ontr ol. To meet these
requirements, Zetex have a range of
high current, high gain transistors
available in E-Line, SOT223 and TO126
that allow converter designs to 100kHz,
and fast charge currents of up to 5A.
Figure 11 shows a circuit designed by
Benchmarq Microelectronics Inc., that
uses the 3A rated ZTX788B for a low cost
fast charger running at typically 80kHz
and supplying a charging current of
2.3A. (This particular circuit being
configured to charge two cells, and will
accept an input voltage up to 15V). The
circuit uses a turn-off circuit devised by
Benchmarq to remove switching losses
associated with bipolar transistor
storage time and turn-off fall time, to
allow the transistors to exhibit similar
switching efficiences to large MOSFETs.
This switch-off circuit is also shown in
Figure 12. Q2 is driven by the PWM
switching controller, and with the
emitter resistor sets the base current for
the high current PNP. These
components are selected to ensure that
on-state losses are acceptable for a
given load condition without incurring
excessive drive loss. When Q2 switches
off, the inductor L1 rings, turning Q1 on
hard. Q2 then performs active pull-up on
the base of Q3 -the switching transistor.
This method, and similar circuit
techniques to remove base charge can
be used to allow cost effective bipolar
DC-DC converters.
AN21- 11
Application Note 21
Issue 2 January 1996
pair of FZT849s or a ZDT1048 SM-8 dual
transistor to produce a 90% efficient
i n v e r t e r . P l e a s e r e f e r to L i n e a r
Technology application note AN65 Oct
9 5 , “ A F ou r t h G e n e r at i o n o f L C D
Backlight Technology” by Jim Williams.
Power Supply Switching
P o w e r s u p p l y s w i tc h i n g f o r l o a d
m a n a g e m e n t ( s u c h a s p e r i ph e r a l
control, transmit circuit blocks in
handphones, and RAM back-up) should
be considered carefully in terms of the
DC and peak currents required; the
allowable voltage drop across the switch
element (the PCMCIA power switching
specification for example, states a 5%
maximum drop at a 1A output, from the
nominal 5V or 3.3V rail); ease of drive
and cost constraints. The FMMT717 is a
SOT23 PNP transistor that exhibits a
best in class VCE(sat) of 100mV at a pass
current of 1A, equating to a switch
resistance of 100mΩ. This on-state
performance also allows a 2.5A DC
capability, providing a power switch for
PCMCIA (peripherals may demand up to
1.5A peak for say hard disc spin-up),
mobile phone battery chargers, and
battery management systems, that is
reliable and offers the most space and
cost efficient solution. To perform the
same function with a P-Channel MOSFET
would require a much larger die (and
therefore package) and therefore an
increase in price and weight for the user.
Analogue IC vendors manufacture
microprocessor
power
supply
supervisory devices, that monitor the
state of memory supply rails and switch
over the supplies as required. These
devices often require a low loss PNP or
P-Channel part as the pass element, and
this function can usually be effected
with much less cost by a suitable PNP
transistor.
Voltage Regulation
Low drop out regulator controller ICs are
now available that provide the user with
the advantages of a monolithic voltage
reference, and the freedom to specify
the output device rele vant to the
application. These devices usually
require a PNP device to function as the
linear drop element. To allow the system
to operate down to the minimum input
voltage as the battery pack reaches the
end of a discharge cycle, implies that the
transistor must exhibit very low VCE(sat),
preferably with a minimal amount of
base drive drawn from the controller IC.
Device
Package
IC (DC)
PD
VCE(sat)
@Ic /Ib
FMMT717
SOT23
2.5A
625mW
100mV
1A /10mA
ZTX788B
E-Line
3A
1W
190mV
1A /5mA
ZTX949
E-Line
4.5A
1.2W
190mV
3A /60mA
ZBD949
TO126
5A
2W/25W
480mV
5A /50mA
Table 4
PNP Transistors for Low Dropout regulator Designs.
AN21- 10
Application Note 21
Issue 2 January 1996
There are a number of Zetex parts ideally
suited for this application, and Table 4
provides an overview of suitable parts.
Fi gur e 10 s ho w s t wo ty pic al L DO
regulator circuits published by Linear
Technology and MAXIM.
620
5.4 - 7.2V
ZBD949
10µF
20
Drive
OUTPUT
= 5V/4A
F/b
LT1123
10µF
Gnd
Input +3.5V to +5V ZTX749
Base
27
In
On
Blim
Out
MAX687
0.47µF
Output 3.3V at 500mA
Gnd
50µF
PFO
CC 10nF
Gnd
Figure 10
Low Drop Out Regulators - IC + Discrete
Implementation.
DC-DC Converters and Fast Chargers
Battery charge management and fast
charge circ uit topologies using
intelligent charge, voltage inflection,
current, and cell temperature
monitoring, frequently employ a DC-DC
converter to effect an efficient charge
transfer between the available source
and the battery pack. This is usually a
step down or Buck converter which
d i c t a t e s a fa i r l y h i g h o p e r a t i n g
f r e q u e n c y (t o m e e t i n d uc t or s i z e
constraints), and is also subject to very
tight cos t c ontr ol. To meet these
requirements, Zetex have a range of
high current, high gain transistors
available in E-Line, SOT223 and TO126
that allow converter designs to 100kHz,
and fast charge currents of up to 5A.
Figure 11 shows a circuit designed by
Benchmarq Microelectronics Inc., that
uses the 3A rated ZTX788B for a low cost
fast charger running at typically 80kHz
and supplying a charging current of
2.3A. (This particular circuit being
configured to charge two cells, and will
accept an input voltage up to 15V). The
circuit uses a turn-off circuit devised by
Benchmarq to remove switching losses
associated with bipolar transistor
storage time and turn-off fall time, to
allow the transistors to exhibit similar
switching efficiences to large MOSFETs.
This switch-off circuit is also shown in
Figure 12. Q2 is driven by the PWM
switching controller, and with the
emitter resistor sets the base current for
the high current PNP. These
components are selected to ensure that
on-state losses are acceptable for a
given load condition without incurring
excessive drive loss. When Q2 switches
off, the inductor L1 rings, turning Q1 on
hard. Q2 then performs active pull-up on
the base of Q3 -the switching transistor.
This method, and similar circuit
techniques to remove base charge can
be used to allow cost effective bipolar
DC-DC converters.
AN21- 11
Application Note 21
Issue 2 January 1996
Application Note 21
Issue 2 January 1996
APPENDIX A
FMMT717 datasheet including absolute maximum ratings, detail sheet and full DC
characterisation.
“SuperSOT”
SOT23 PNP SILICON POWER
(SWITCHING) TRANSISTOR
FMMT717
FEATURES
*
625mW POWER DISSIPATION
*
*
*
*
IC CONT 2.5A
10A PEAK PULSE CURRENT
EXCELLENT HFE CHARACTERISTICS UP TO 10A (PULSED)
LOW SATURATION VOLTAGE
E
C
B
COMPLEMENTARY TYPE – FMMT617
PARTMARKING DETAIL – 717
SOT23
Figure 11
Fast Charge Circuit (Benchmarq Microelectronics) using the ZTX788B.
ABSOLUTE MAXIMUM RATINGS.
PARAMETER
L2
ZTX788B
Input
Q3
150µ
µH
Q1
2N3904 1K
1N5820
L1
10µ
µH
+Bat
10µ
µF
1N4148
Q2
2N3904
Drive
Feedback
68
Figure 12
Turn-off circuit for Bipolar Transistors, allowing High Efficiency DC-DC Conversion at
High Frequency.
AN21- 12
SYMBOL
VALUE
UNIT
V
Collector-Base Voltage
VCBO
-12
Collector-Emitter Voltage
VCEO
-12
V
Emitter-Base Voltage
VEBO
-5
V
Peak Pulse Current **
ICM
-10
A
Continuous Collector Current
IC
-2.5
A
Base Current
IB
-500
mA
Power Dissipation at T amb=25°C*
Ptot
-625
mW
Operating and Storage Temperature Range
Tj:Tstg
-55 to +150
°C
*Maximum power dissipation is calculated assuming that the device is mounted on a
ceramic substrate measuring 15x15x0.6mm
**Measured under pulsed conditions. Pulse width=300µs. Duty cycle ≤ 2%
AN21- 13
Application Note 21
Issue 2 January 1996
Application Note 21
Issue 2 January 1996
APPENDIX A
FMMT717 datasheet including absolute maximum ratings, detail sheet and full DC
characterisation.
“SuperSOT”
SOT23 PNP SILICON POWER
(SWITCHING) TRANSISTOR
FMMT717
FEATURES
*
625mW POWER DISSIPATION
*
*
*
*
IC CONT 2.5A
10A PEAK PULSE CURRENT
EXCELLENT HFE CHARACTERISTICS UP TO 10A (PULSED)
LOW SATURATION VOLTAGE
E
C
B
COMPLEMENTARY TYPE – FMMT617
PARTMARKING DETAIL – 717
SOT23
Figure 11
Fast Charge Circuit (Benchmarq Microelectronics) using the ZTX788B.
ABSOLUTE MAXIMUM RATINGS.
PARAMETER
L2
ZTX788B
Input
Q3
150µ
µH
Q1
2N3904 1K
1N5820
L1
10µ
µH
+Bat
10µ
µF
1N4148
Q2
2N3904
Drive
Feedback
68
Figure 12
Turn-off circuit for Bipolar Transistors, allowing High Efficiency DC-DC Conversion at
High Frequency.
AN21- 12
SYMBOL
VALUE
UNIT
V
Collector-Base Voltage
VCBO
-12
Collector-Emitter Voltage
VCEO
-12
V
Emitter-Base Voltage
VEBO
-5
V
Peak Pulse Current **
ICM
-10
A
Continuous Collector Current
IC
-2.5
A
Base Current
IB
-500
mA
Power Dissipation at T amb=25°C*
Ptot
-625
mW
Operating and Storage Temperature Range
Tj:Tstg
-55 to +150
°C
*Maximum power dissipation is calculated assuming that the device is mounted on a
ceramic substrate measuring 15x15x0.6mm
**Measured under pulsed conditions. Pulse width=300µs. Duty cycle ≤ 2%
AN21- 13
Application Note 21
Issue 2 January 1996
Application Note 21
Issue 2 January 1996
ELECTRICAL CHARACTERISTICS (at Tamb = 25°C unless otherwise
stated).
PARAMETER
SYMBOL
MIN.
TYP.
Collector-Base
Breakdown Voltage
V (BR)CBO
-12
Collector-Emitter
Breakdown Voltage
V(BR)CEO
-12
Emitter-Base
Breakdown Voltage
V(BR)EBO
MAX.
UNIT
CONDITIONS.
-35
V
IC=-100µA
-25
V
IC=-10mA*
TYPICAL CHARACTERISTICS
1
0.8
+25°C
IC/IB=10
0.7
Collector Cut-Off
Current
ICBO
-100
nA
VCB=-10V
Emitter Cut-Off
Current
IEBO
-100
nA
VEB=-4V
Collector Emitter
Cut-Off Current
ICES
-100
Collector-Emitter
Saturation Voltage
VCE(sat)
-17
-140
-170
-220
mV
mV
mV
mV
IC=-0.1A, IB=-10mA*
IC=-1A, IB=-10mA*
IC=-1.5A, IB=-50mA*
IC=-2.5A, IB=-50mA*
-0.9
-1.0
V
IC=-2.5A, IB=-50mA*
VBE(on)
Static Forward
Current Transfer
Ratio
hFE
Transition
Frequency
fT
Output Capacitance
Cobo
21
Turn-On Time
t(on)
70
Turn-Off Time
t(off)
130
-0.8
-1.0
V
475
450
275
100
70
80
110
1
0.0
1mA
10
100mA
1A
Collector Current
VCE(SAT) vs IC
10A
100A
10A
100A
1.6
IC=-50mA, VCE=-10V
f=100MHz
pF
V CB=-10V, f=1MHz
V CC=-6V, IC=-2A
IB1=IB2=50mA
IC/IB=10
1.4
450
1.2
25°C
1.0
0.8
225
-55°C
0.6
0.4
0.0
100mA
1A
10A
1.2
1.0
-55°C
0.8
25°C
100°C
0.6
0.4
0.2
0
10mA
0.0
1mA
100A
10mA
hFE vs IC
1.2
100mA
1A
Collector Current
Collector Current
VBE(SAT) vs IC
10
SINGLE PULSE TEST Tamb = 25 deg C
VCE=2V
1.0
0.8
-55°C
25°C
0.6
100°C
0.4
1.0
0.1
D.C.
1s
100ms
10ms
1ms
100µs
0.2
0.0
1mA
10mA
100mA
1A
10A
100A
0.01
0.1
1.0
10
VCE (VOLTS)
Collector Current
VBE(ON) vs IC
AN21- 14
10mA
VCE(SAT) vs IC
0.2
IC =-2.5A, V CE=-2V*
MHz
*Measured under pulsed conditions. Pulse width=300µs. Duty cycle ≤ 2%
0.2
VCE=2V
IC=-10mA, VCE=-2V*
IC=-100mA, VCE=-2V*
IC=-2.5A, VCE=-2V*
IC=-8A, VCE=-2V*
IC=-10A, VCE=-2V*
30
100°C
25°C
-55°C
0.3
Collector Current (A)
100°C
1mA
300
300
180
60
45
100m
1.4
Normalised Gain
-10
-100
-110
-180
Base-Emitter
Turn-On Voltage
10m
0.4
VCES=-10V
1.6
VBE(sat)
VCE (VOLTS)
VCE(sat) - (V)
1m
0.5
0.1
1m
VBE (VOLTS)
Base-Emitter
Saturation Voltage
nA
IC/IB=100
IC/IB=50
IC/IB=30
IC/IB=10
IE=-100µA
VBE (VOLTS)
V
10m
IC (AMPS)
-8.5
100m
Typical Gain (hFE)
-5
0.6
Safe Operating Area
AN21- 15
100
Application Note 21
Issue 2 January 1996
Application Note 21
Issue 2 January 1996
ELECTRICAL CHARACTERISTICS (at Tamb = 25°C unless otherwise
stated).
PARAMETER
SYMBOL
MIN.
TYP.
Collector-Base
Breakdown Voltage
V (BR)CBO
-12
Collector-Emitter
Breakdown Voltage
V(BR)CEO
-12
Emitter-Base
Breakdown Voltage
V(BR)EBO
MAX.
UNIT
CONDITIONS.
-35
V
IC=-100µA
-25
V
IC=-10mA*
TYPICAL CHARACTERISTICS
1
0.8
+25°C
IC/IB=10
0.7
Collector Cut-Off
Current
ICBO
-100
nA
VCB=-10V
Emitter Cut-Off
Current
IEBO
-100
nA
VEB=-4V
Collector Emitter
Cut-Off Current
ICES
-100
Collector-Emitter
Saturation Voltage
VCE(sat)
-17
-140
-170
-220
mV
mV
mV
mV
IC=-0.1A, IB=-10mA*
IC=-1A, IB=-10mA*
IC=-1.5A, IB=-50mA*
IC=-2.5A, IB=-50mA*
-0.9
-1.0
V
IC=-2.5A, IB=-50mA*
VBE(on)
Static Forward
Current Transfer
Ratio
hFE
Transition
Frequency
fT
Output Capacitance
Cobo
21
Turn-On Time
t(on)
70
Turn-Off Time
t(off)
130
-0.8
-1.0
V
475
450
275
100
70
80
110
1
0.0
1mA
10
100mA
1A
Collector Current
VCE(SAT) vs IC
10A
100A
10A
100A
1.6
IC=-50mA, VCE=-10V
f=100MHz
pF
V CB=-10V, f=1MHz
V CC=-6V, IC=-2A
IB1=IB2=50mA
IC/IB=10
1.4
450
1.2
25°C
1.0
0.8
225
-55°C
0.6
0.4
0.0
100mA
1A
10A
1.2
1.0
-55°C
0.8
25°C
100°C
0.6
0.4
0.2
0
10mA
0.0
1mA
100A
10mA
hFE vs IC
1.2
100mA
1A
Collector Current
Collector Current
VBE(SAT) vs IC
10
SINGLE PULSE TEST Tamb = 25 deg C
VCE=2V
1.0
0.8
-55°C
25°C
0.6
100°C
0.4
1.0
0.1
D.C.
1s
100ms
10ms
1ms
100µs
0.2
0.0
1mA
10mA
100mA
1A
10A
100A
0.01
0.1
1.0
10
VCE (VOLTS)
Collector Current
VBE(ON) vs IC
AN21- 14
10mA
VCE(SAT) vs IC
0.2
IC =-2.5A, V CE=-2V*
MHz
*Measured under pulsed conditions. Pulse width=300µs. Duty cycle ≤ 2%
0.2
VCE=2V
IC=-10mA, VCE=-2V*
IC=-100mA, VCE=-2V*
IC=-2.5A, VCE=-2V*
IC=-8A, VCE=-2V*
IC=-10A, VCE=-2V*
30
100°C
25°C
-55°C
0.3
Collector Current (A)
100°C
1mA
300
300
180
60
45
100m
1.4
Normalised Gain
-10
-100
-110
-180
Base-Emitter
Turn-On Voltage
10m
0.4
VCES=-10V
1.6
VBE(sat)
VCE (VOLTS)
VCE(sat) - (V)
1m
0.5
0.1
1m
VBE (VOLTS)
Base-Emitter
Saturation Voltage
nA
IC/IB=100
IC/IB=50
IC/IB=30
IC/IB=10
IE=-100µA
VBE (VOLTS)
V
10m
IC (AMPS)
-8.5
100m
Typical Gain (hFE)
-5
0.6
Safe Operating Area
AN21- 15
100
Application Note 21
Issue 2 January 1996
THERMAL CHARACTERISTICS
DERATING CURVE
MAXIMUM TRANSIENT THERMAL RESISTANCE
* Reference above figures, Devices were mounted on a 15mmx15mm ceramic
NOTE: Spice parameter data for FMMT717 can be provided upon request.
AN21- 16
Application Note 21
Issue 2 January 1996
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