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PDF NCP7662 Data sheet ( Hoja de datos )
| Número de pieza | NCP7662 | |
| Descripción | INDUCTORLESS VOLTAGE CONVERTER | |
| Fabricantes | ON Semiconductor | |
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Hay una vista previa y un enlace de descarga de NCP7662 (archivo pdf) en la parte inferior de esta página. Total 12 Páginas | ||
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NCP7662
Inductorless Voltage
Converter
The NCP7662 is a pin–compatible upgrade to the industry standard
TC7660 charge pump voltage converter. It converts a +1.5 V to +15 V
input to a corresponding –1.5 to –15 V output using only two low–cost
capacitors, eliminating inductors and their associated cost, size and
EMI.
The on–board oscillator operates at a nominal frequency of 10 kHz.
Frequency is increased to 35 kHz when pin 1 is connected to V+,
allowing the use of smaller external capacitors. Operation below 10 kHz
(for lower supply current applications) is also possible by connecting an
external capacitor from OSC to ground (with pin 1 open).
The NCP7662 is available in both 8–pin DIP and 8–pin small outline
(SO) packages in commercial and extended temperature ranges.
Features
• Wide Operating Voltage Range: 1.5 V to 15 V
• Boost Pin (Pin 1) for Higher Switching Frequency
• High Power Efficiency is 96%
• Easy to Use – Requires Only 2 External Non–Critical Passive
Components
• Improved Direct Replacement for Industry Standard ICL7660 and
Other Second Source Devices
www.DataSheet4U.com
Applications
"• Simple Conversion of +5 V to 5 V Supplies
"• Voltage Multiplication VOUT = nVIN
• Negative Supplies for Data Acquisition Systems and Instrumentation
• RS232 Power Supplies
"• Supply Splitter, VOUT = VS/2
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8
1
SO–8
D SUFFIX
CASE 751
MARKING
DIAGRAMS
8
NCP
7662
YWWXZ
1
8
1
PDIP–8
P SUFFIX
CASE 626
8
NCP7662
YYWWXZ
CO
1
YY, Y
WW
X
Z
CO
= Year
= Work Week
= Assembly ID Code
= Subcontractor ID Code
= Country of Orgin
PIN CONNECTIONS
BOOST 1
CAP+ 2
GND 3
CAP– 4
8 V+
7 OSC
6
LOW
VOLTAGE (LV)
5 VOUT
ORDERING INFORMATION
Device
Package
Shipping
NCP7662DR2
SO–8 2500 Tape & Reel
NCP7662P
PDIP–8
50 Units/Rail
© Semiconductor Components Industries, LLC, 2000
June, 2000 – Rev. 0
1
Publication Order Number:
NCP7662/D
1 page  
NCP7662
TYPICAL APPLICATIONS
Simple Negative Voltage Converter
The majority of applications will undoubtedly utilize the
NCP7662 for generation of negative supply voltages.
Figure 3 shows typical connections to provide a negative
supply where a positive supply of +1.5 V to +15 V is
available. Keep in mind that pin 6 (LV) is tied to the supply
negative (GND) for supply voltages below 3.5 volts.
V+
10 µF
+
–
1
2
3
4
8
7
6
5
10
µF
–
+
RO
VOUT = –V+
–
V+
+
VOUT
(a) (b)
Figure 3. Simple Negative Converter
and its Output Equivalent
The output characteristics of the circuit in Figure 3 can be
approximated by an ideal voltage source in series with a
resistance as shown in Figure 3b. The voltage source has a
value of –(V+). The output impedance (RO) is a function of
the ON resistance of the internal MOS switches (shown in
Figure 2), the switching frequency, the value of C1 and C2,
and the ESR (equivalent series resistance) of C1 and C2. A
good first order approximation for RO is:
RO ^ 2(RSW1 ) RSW3 ) ESRC1) ) 2(RSW2 ) RSW4
)
ESRC1) )
1
fPUMP
C1 ) ESRC2
+ +(fPUMP
fOSC
2
,
RSWX
MOSFET switch resistance)
Combining the four RSWX terms as RSW, we see that:
RO ^ 2
)RSW
1
fPUMP
C1 ) 4
ESRC1
) ESRC2Ω
RSW, the total switch resistance, is a function of supply
voltage and temperature (see the Output Source Resistance
graphs), typically 23 Ω at +25°C and 5 V. Careful selection
of C1 and C2 will reduce the remaining terms, minimizing
the output impedance. High value capacitors will reduce the
1/(fPUMP C1) component, and low ESR capacitors will
lower the ESR term. Increasing the oscillator frequency will
reduce the 1/(fPUMP C1) term, but may have the side
ueffect of a net increase in output impedance when C1
10 µF and there is not enough time to fully charge the
capacitors every cycle. In a typical application when fOSC =
10 kHz and C = C1 = C2 = 10 µF:
^ )RO
2
23
5
1
103 10
10–6)
) 4 )ESRC1 ESRC2
RO ^ (46 ) 20 ) 5 ESRC) Ω
Since the ESRs of the capacitors are reflected in the output
impedance multiplied by a factor of 5, a high value could
potentially swamp out a low 1/(fPUMP C1) term,
rendering an increase in switching frequency or filter
capacitance ineffective. Typical electrolytic capacitors may
have ESRs as high as 10 Ω.
Output Ripple
ESR also affects the ripple voltage seen at the output. The
total ripple is determined by 2 voltages, A and B, as shown
in Figure 4. Segment A is the voltage drop across the ESR
of C2 at the instant it goes from being charged by C1 (current
flowing into C2) to being discharged through the load
(current flowing out of C2). The magnitude of this current
change is 2 IOUT, hence the total drop is 2 IOUT
ESRC2 volts. Segment B is the voltage change across C2
during time t2, the half of the cycle when C2 supplies current
to the load. The drop at B is IOUT t2/C2 volts. The
peak–to–peak ripple voltage is the sum of these voltage
ǒdrops:
^VRIPPLE
2
1
fPUMP
C2 ) ESRC2
ǓIOUT
t2 t1
0
V
–(V+)
B
A
Figure 4. Output Ripple
Paralleling Devices
Any number of NCP7662 voltage converters may be
paralleled to reduce output resistance (Figure 5). The
reservoir capacitor, C2, serves all devices, while each device
requires its own pump capacitor, C1. The resultant output
resistance would be approximately:
+ROUT
ROUT (of NCP7662)
n (number of devices)
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5
5 Page 
Notes
NCP7662
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11
11 Page | ||
| Páginas | Total 12 Páginas | |
| PDF Descargar | [ Datasheet NCP7662.PDF ] | |
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