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PDF MAX1720 Data sheet ( Hoja de datos )
| Número de pieza | MAX1720 | |
| Descripción | Switched Capacitor Voltage Inverter | |
| Fabricantes | ON Semiconductor | |
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MAX1720
Switched Capacitor Voltage
Inverter with Shutdown
The MAX1720 is a CMOS charge pump voltage inverter that is
designed for operation over an input voltage range of 1.15 V to 5.5 V
with an output current capability in excess of 50 mA. The operating
current consumption is only 67 mA, and a power saving shutdown
input is provided to further reduce the current to a mere 0.4 mA. The
device contains a 12 kHz oscillator that drives four low resistance
MOSFET switches, yielding a low output resistance of 26 W and a
voltage conversion efficiency of 99%. This device requires only two
external 10 mF capacitors for a complete inverter making it an ideal
solution for numerous battery powered and board level applications.
The MAX1720 is available in the space saving TSOP−6 package.
Features
• Operating Voltage Range of 1.15 V to 5.5 V
• Output Current Capability in Excess of 50 mA
• Low Current Consumption of 67 mA
• Power Saving Shutdown Input for a Reduced Current of 0.4 mA
• Operation at 12 kHz
• Low Output Resistance of 26 W
• Space Saving TSOP−6 Package
• Pb−Free Package is Available
Typical Applications
• LCD Panel Bias
• Cellular Telephones
• Pagers
• Personal Digital Assistants
• Electronic Games
• Digital Cameras
• Camcorders
• Hand Held Instruments
−Vout
16
Vin 2
3
5
4
This device contains 77 active transistors.
Figure 1. Typical Application
© Semiconductor Components Industries, LLC, 2005
December, 2005 − Rev. 3
1
http://onsemi.com
6
1
TSOP−6
SN SUFFIX
CASE 318G
MARKING DIAGRAM
EACAYW G
G
1
EAC = Device Code
A = Assembly Location
Y = Year
W = Work Week
G = Pb−Free Package
(Note: Microdot may be in either location)
PIN CONNECTIONS
Vout 1
6 C+
Vin 2
5 SHDN
C− 3
4 GND
(Top View)
ORDERING INFORMATION
Device
Package
Shipping†
MAX1720EUT TSOP−6 3000 Tape & Reel
MAX1720EUTG TSOP−6 3000 Tape & Reel
(Pb−Free)
†For information on tape and reel specifications,
including part orientation and tape sizes, please
refer to our Tape and Reel Packaging Specifications
Brochure, BRD8011/D.
Publication Order Number:
MAX1720/D
1 page  
MAX1720
1
OSC
Vin + 2
C3
3
6
5
4
−Vout
+C2 RL
+
C1
C1 = C2 = C3 = 10 mF
Figure 14. Test Setup/Voltage Inverter
DETAILED OPERATING DESCRIPTION
The MAX1720 charge pump converter inverts the voltage
applied to the Vin pin. Conversion consists of a two−phase
operation (Figure 15). During the first phase, switches S2 and
S4 are open and S1 and S3 are closed. During this time, C1
charges to the voltage on Vin and load current is supplied from
C2. During the second phase, S2 and S4 are closed, and S1 and
S3 are open. This action connects C1 across C2, restoring
charge to C2.
S1
Vin
S2
C1
S3
From Osc
C2
S4
−Vout
Figure 15. Ideal Switched Capacitor Charge Pump
APPLICATIONS INFORMATION
Output Voltage Considerations
The MAX1720 performs voltage conversion but does not
provide regulation. The output voltage will drop in a linear
manner with respect to load current. The value of this
equivalent output resistance is approximately 26 W nominal
at 25°C with Vin = 5.0 V. Vout is approximately −5.0 V at light
loads, and drops according to the equation below:
VDROP + Iout Rout
Vout + * (Vin * VDROP)
Charge Pump Efficiency
The overall power conversion efficiency of the charge
pump is affected by four factors:
1. Losses from power consumed by the internal
oscillator, switch drive, etc. (which vary with input
voltage, temperature and oscillator frequency).
2. I2R losses due to the on−resistance of the MOSFET
switches on−board the charge pump.
3. Charge pump capacitor losses due to Equivalent
Series Resistance (ESR).
4. Losses that occur during charge transfer from the
commutation capacitor to the output capacitor when
a voltage difference between the two capacitors
exists.
Most of the conversion losses are due to factors 2, 3 and 4.
These losses are given by Equation 1.
PLOSS(2,3,4) + Iout 2 Rout ^ Iout 2
ƪ ƫ1
(fOSC)C1
)
8RSWITCH
)
4ESRC1
)
ESRC2
(eq. 1)
The 1/(fOSC)(C1) term in Equation 1 is the effective output
resistance of an ideal switched capacitor circuit (Figures 16
and 17).
The losses due to charge transfer above are also shown in
Equation 2. The output voltage ripple is given by Equation 3.
PLOSS + [ 0.5C 1 (Vin2 * Vout2)
) 0.5C2 (VRIPPLE2 * 2VoutVRIPPLE)]
fOSC
(eq. 2)
VRIPPLE
+
Iout
(fOSC)(C2)
)
2(Iout)(ESRC2)
(eq.
3)
f
Vin
Vout
C1 C2 RL
Figure 16. Ideal Switched Capacitor Model
REQUIV
Vin
REQUIV + f
1
C1
Vout
C2 RL
Figure 17. Equivalent Output Resistance
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5
5 Page 
MAX1720
A zener diode can be used with the shutdown input to provide closed loop regulation performance. This significantly reduces
the converter’s output resistance and dramatically enhances the load regulation. For closed loop operation, the desired
regulated output voltage must be lower in magnitude than −Vin. The output will regulate at a level of −VZ + V .th(SHDN) Note that
the shutdown input voltage threshold is typically 0.5 Vin and therefore, the regulated output voltage will change proportional
to the converter’s input. This characteristic will not present a problem when used in applications with constant input voltage.
In this case the zener breakdown was measured at 25 mA. The performance characteristics for the above converter are shown
below. Note that the dashed curve sections represent the converter’s open loop performance.
−1.0
−2.0
−3.0
TA = 25°C
A
−4.0
B
Curve
A
B
Vin (V)
3.3 V
5.0 V
Vz (V)
4.5
6.5
Vout (V)
−2.8
−3.8
−5.0
0
10 20 30 40 50 60
Iout, OUTPUT CURRENT (mA)
Figure 31. Load Regulation, Output Voltage vs.
Output Current
1
OSC
6
Vin + 2
5
34
−Vout
+
R1
+ R2
10 k
Capacitors = 10 mF
Figure 32. Line and Load Regulated Negative Output Voltage
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11
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| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX1720.PDF ] | |
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