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PDF ZXM64NO3X Data sheet ( Hoja de datos )
| Número de pieza | ZXM64NO3X | |
| Descripción | HIGH EFFICIENCY SIMPLESYNC PWM DC-DC CONTROLLERS | |
| Fabricantes | Zetex Semiconductors | |
| Logotipo |  |
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ZXRD1000 SERIES
HIGH EFFICIENCY SIMPLESYNC PWM DC-DC CONTROLLERS
DESCRIPTION
The ZXRD1000 series provides complete control and
protection functions for a high efficiency (> 95%) DC-DC
converter solution. The choice of external MOSFETs allow
the designer to size devices according to application. The
ZXRD1000 series uses advanced DC-DC converter
techniques to provide synchronous drive capability, using
innovative circuits that allow easy and cost effective
implementation of shoot through protection. The
FEATURES
• > 95% Efficiency
• Fixed frequency (adjustable) PWM
• Voltage mode to ensure excellent stability &
transient response
• Low quiescent current in shutdown mode,15µA
• Low battery flag
• Output down to 2.0V
• Overload protection
• Demonstration boards available
• Synchronous or non-synchronous operation
• Cost effective solution
• N or P channel MOSFETs
• QSOP16 package
ZXRD1000 series can be used with an all N channel
topology or a combination N & P channel topology.
Additional functionality includes shutdown control, a
user adjustable low battery flag and simple
adjustment of the fixed PWM switching frequency.
The controller is available with fixed outputs of 5V or
3.3V and an adjustable (2.0 to 12V) output.
• Fixed 3.3, 5V and adjustable outputs
• Programmable soft start
APPLICATIONS
• High efficiency 5 to 3.3V converters up to 4A
• Sub-notebook computers
• Embedded processor power supply
• Distributed power supply
• Portable instruments
• Local on card conversion
• GPS systems
Very high efficiency SimpleSyncTM converter.
VCC
4.5-10V
Shut Down
Low input flag
CIN
68µF
R1
100k
IC1
9 SHDN
13
VIN
VDRIVE 2
C10
1µF
C1
1µF
C5 LBSET Bootstrap 1
1µF
11 LBF
RSENSE+ 7
C2 330pF
1µF C3
14
10
6
5
Delay
Decoup
VINT
CT
GND
4
1µF
C4
RSENSE - 8
VFB 16
Comp
PWR
15
GND
3
C7
22µF
C6
1µF
R6820RC0X.0122µF
RX
2k7
R4
10k
D2
BAT54
ZXM64N02X
N1
C11
1µF
L1
15µH
Fx
D3
BAT54
N2
ZXM64N02X
C8
D1 2.2µF
ZHCS1000
R3
3k
RSENSE
0.01R
VOUT
3.3V 4A
R6 Cx2
10k
0.01µF
COUT
x2
680µF 120µF
R5
6k
C9
1µF
ISSUE 4 - OCTOBER 2000
1
1 page  
ZXRD1000 SERIES
DETAILED DESCRIPTION
The ZXRD1000 series can be configured to use either
N or P channel MOSFETs to suit most applications.
The most popular format, an all N channel
synchronous solution gives the optimum efficiency. A
feature of the ZXRD1000 series solution is the unique
method of generating the synchronous drive, called
SimpleSync . Most solutions use an additional
output from the controller, inverted and delayed from
the main switch drive. The ZXRD1000 series solution
uses a simple overwinding on the main choke (wound
on the same core at no real cost penalty) plus a small
ferrite bead . This means that the synchronous FET is
only enhanced when the main FET is turned off. This
reduces the ‘blanking period’ required for shoot-
through protection, increasing efficiency and allowing
smaller catch diodes to be used, making the controller
simpler and less costly by avoiding complex timing
circuitry. Included on chip are numerous functions that
allow flexibility to suit most applications. The nominal
switching frequency (200kHz) can be adjusted by a
simple timing capacitor, C3. A low battery detect circuit
is also provided. Off the shelf components are available
from major manufacturers such as Sumida to provide
either a single winding inductor for non-synchronous
applications or a coil with an over-winding for
synchronous applications. The combination of these
switching characteristics, innovative circuit design and
excellent user flexibility, make the ZXRD1000 series
DC-DC solutions some of the smallest and most cost
effective and electrically efficient currently available.
Using Zetex’s HDMOS low RDS(on) devices, ZXM64N02X
for the main and synchronous switch, efficiency can
peak at upto 95% and remains high over a wide range
of operating currents. Programmable soft start can also be
adjusted via the capacitor, C7, in the compensation loop.
What is SimpleSyncTM?
Conventional Methods
In the conventional approach to the synchronous
DC-DC solution, much care has to be taken with the
timing constraints between the main and synchronous
switching devices. Not only is this dependent upon
individual MOSFET gate thresholds (which vary from
device to device within data sheet limits and over
temperature), but it is also somewhat dependent upon
magnetics, layout and other parasitics. This normally
means that significant ‘dead time’ has to be factored
in to the design between the main and synchronous
devices being turned off and on respectively.
Incorrect application of dead time constraints can
potentially lead to catastrophic short circuit conditions
between VIN and GND. For some battery operated
systems this can not only damage MOSFETs, but also
the battery itself. To realise correct ‘dead time’
implementation takes complex circuitry and hence
implies additional cost.
The ZETEX Method
Zetex has taken a different approach to solving these
problems. By looking at the basic architecture of a
synchronous converter, a novel approach using the
main circuit inductor was developed. By taking the
inverse waveform found at the input to the main
inductor of a non-synchronous solution, a
synchronous drive waveform can be generated that is
always relative to the main drive waveform and
inverted with a small delay. This waveform can be
used to drive the synchronous switch which means no
complex circuitry in the IC need be used to allow for
shoot-through protection.
Implementation
Implementation was very easy and low cost. It simply
meant peeling off a strand of the main inductor
winding and isolating it to form a coupled secondary
winding. These are available as standard items
referred to in the applications circuits parts list.The use
of a small, surface mount, inexpensive ’square loop’
ferrite bead provides an excellent method of
eliminating shoot-through due to variation in gate
thresholds. The bead essentially acts as a high
impedance for the few nano seconds that
shoot-through would normally occur. It saturates very
quickly as the MOSFETs attain steady state operation,
reducing the bead impedance to virtually zero.
Benefits
The net result is an innovative solution that gives
additional benefits whilst lowering overall
implementation costs. It is also a technique that can
be simply omitted to make a non-synchronous
controller, saving further cost, at the expense of a few
efficiency points.
ISSUE 4 - OCTOBER 2000
5
5 Page 
VCC
4.5-10V
Shut Down
Low input flag
CIN
68µF
R1
100k
IC1
9 SHDN
13
VIN
VDRIVE 2
C10
1µF
C1
1µF
C5 LBSET Bootstrap 1
1µF
11 LBF
RSENSE+ 7
C2 330pF
1µF C3
14
10
6
5
Delay
Decoup
VINT
CT
GND
4
1µF
C4
RSENSE - 8
VFB 16
Comp
PWR
15
GND
3
C7
22µF
C6
1µF
6R820RC0X.0122µF
RX
2k7
R4
10k
D2
BAT54
ZXM64N02X
N1
C11
1µF
L1
15µH
Fx
D3
BAT54
N2
ZXM64N02X
C8
D1 2.2µF
ZHCS1000
R3
3k
RSENSE
0.01R
VOUT
3.3V 4A
R6 Cx2
10k
0.01µF
COUT
x2
R5 680µF 120µF
6k
C9
1µF
Optimised Transient Response, 4.5V-10V Input, 3V/4A Output, N Phase Adjustable, SimpleSyncTM converter 200kHz.
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet ZXM64NO3X.PDF ] | |
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