ON MAX829SNTR Switched capacitor voltage converter Datasheet

MAX828 MAX829
Switched Capacitor
Voltage Converters
The MAX828/829 are CMOS “charge–pump” voltage converters in
ultra–small SOT–23 5 lead packages. They invert and/or double an
input voltage which can range from +1.5V to +5.5V. Conversion
efficiency is typically >95%. Switching frequency is 12kHz for the
MAX828 and 35kHz for the MAX829.
External component requirement is only two capacitors (3.3µF
nominal) for standard voltage inverter applications. With a few
additional components a positive doubler can also be built. All other
circuitry, including control, oscillator, power MOSFETs are integrated
on–chip. Supply current is 50 µA (MAX828) and 115 µA (MAX829).
The MAX828 and MAX829 are available in a SOT–23 5 lead
surface mount package.
Features
•
•
•
•
•
•
•
•
Charge Pump in SOT–23 5 Lead Package
>95% Voltage Conversion Efficiency
Voltage Inversion and/or Doubling
Low 50 µA (MAX828) Quiescent Current
Operates from +1.5V to +5.5V
Up to 25 mA Output Current
Only Two External Capacitors Required
Tested Operating Temperature Range: –40°C to +85°C
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SOT–23–5
SN SUFFIX
CASE TBD
PRELIMINARY INFORMATION
PIN CONFIGURATION
(Top View)
OUT
1
Vin
2
C–
3
Typical Applications
•
•
•
•
•
4 GND
SOT–23–5*
LCD Panel Bias
Cellular Phones
Pagers
PDAs, Portable Dataloggers
Battery–Powered Devices
NOTE: *SOT–23–5 is equivalent to EIAJ–SC74A
ORDERING INFORMATION
TYPICAL OPERATING CIRCUIT
Device
Voltage Inverter
C+
Vin
C–
MAX828
MAX829
C1
 Semiconductor Components Industries, LLC, 1999
Shipping
MAX828SNTR
SOT–23–5
3000 Tape/Reel
MAX829SNTR
SOT–23–5
3000 Tape/Reel
V–
OUTPUT
OUT
GND
Package
INPUT
+
February, 2000 – Rev. 0
5 C+
+
C2
1
Publication Order Number:
MAX828/D
MAX828 MAX829
PIN DESCRIPTION
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Pin No.
Symbol
Description
1
OUT
Inverting charge pump output
2
VIN
C–
Positive power supply input
3
4
GND
Ground
4
C+
Commutation capacitor negative terminal
Commutation capacitor positive terminal
ABSOLUTE MAXIMUM RATINGS*
Symbol
Value
Unit
Input Voltage (VIN to GND)
Parameter
+6.0, – 0.3
V
Output Voltage (OUT to GND)
–6.0, +0.3
V
50
mA
Current at OUT Pin
Short–Circuit Duration – OUT to GND
TA
Operating Temperature Range
PD
Power Dissipation (TA ≤ 70°C) SOT–23–5
Derate by 4mW/°C for TA > 70°C
Tstg
Storage Temperature Range
Tsol
Lead Temperature (Soldering, 10 Seconds)
Indefinite
–40 to +85
°C
240
mW
–65 to +150
°C
+300
°C
* Maximum Ratings are those values beyond which damage to the device may occur.
ELECTRICAL CHARACTERISTICS (TA = 0°C to +85°C, VIN = +5V, C1 = C2 = 10µF (MAX828), C1 = C2 = 3.3µF (MAX829), unless
otherwise noted. Typical values are at TA = 25°C.)
Symbol
Min
Typ
Max
Supply Current (TA = 25°C)
MAX828
MAX829
—
—
50
115
90
260
V+
Supply Voltage Range (RLOAD = 10kW)
—
—
5.5
FOSC
Oscillator Frequency (TA = 25°C)
MAX828
MAX829
8.4
24.5
12
35
15.6
45.5
—
96
—
95
99.9
—
—
25
—
IDD
PEFF
Characteristic
Unit
µA
Power Efficiency
ILOAD = 3mA, TA = 25°C
V
kHz
%
VEFF
Voltage Conversion Efficiency (RLOAD =
ROUT
Output Resistance (Note 1.)
IOUT = 5mA, TA = 25°C
TA = 0°C to +85°C
R)
%
W
50
65
1. Capacitors C1 and C2 contribution is approximately 20% of the output impedance. For additional information, refer to Equation 1 in the
Applications Information section.
ELECTRICAL CHARACTERISTICS (TA = –40°C to +85°C, VIN = +5V, C1 = C2 = 10µF (MAX828), C1 = C2 = 3.3µF (MAX829),
unless otherwise noted. Typical values are at TA = 25°C.) (Note 2.)
Characteristic
Min
Typ
Max
Supply Current
MAX828
MAX829
—
—
—
—
115
325
Vin
Supply Voltage Range (RLOAD = 10kW)
1.5
—
5.5
FOSC
Oscillator Frequency
MAX828
MAX829
6.0
19
—
—
20
54.3
—
—
65
Symbol
IDD
Unit
µA
V
kHz
ROUT
Output Resistance (IOUT = 5mA)
2. All –40°C to +85°C specifications are guaranteed by design.
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2
W
MAX828 MAX829
DETAILED OPERATING DESCRIPTION
The MAX828/829 charge pump converters invert the
voltage applied to the VIN pin. Conversion consists of a
two–phase operation (Figure 1). 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
(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) above. These losses are given by Equation 1.
ƪ
S2
MAX828/829
R
OUT
^ IOUT
ƫ
2
)C1
Equation 1.
The 1/(fOSC)(C1) term in Equation 1 is the effective output
resistance of an ideal switched capacitor circuit (Figures 2a,
2b).
The losses in the circuit due to factor (4) above are also
shown in Equation 2. The output voltage ripple is given by
Equation 3.
C2
S3
OSC
2
) 8RSWITCH ) 4ESRC1 ) ESRC2
1
(f
IN
C1
+ IOUT
P
LOSS(2,3,4)
S4
Vout = –(Vin)
ƪ
P
LOSS(4)
+
(V
ƪ
(0.5)(C1)( V 2
IN
2
RIPPLE
* VOUT ) ) (0.5)(C2)
2
* 2VOUT VRIPPLE)
ƫ
f
OSC
Equation 2.
Figure 1. Ideal Switched Capacitor Charge Pump
V
RIPPLE
APPLICATIONS INFORMATION
+ (f
I
OUT
)(C2)
OSC
) 2(IOUT)(ESRC2)
Equation 3.
Output Voltage Considerations
The MAX828/829 perform voltage conversion but do 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 25W nominal
at +25°C and VIN = +5V. VOUT is approximately - 5V at light
loads, and droops according to the equation below:
f
V+
Vout
C1
VDROP = IOUT x ROUT
VOUT = – (VIN – VDROP)
C2
RL
Figure 2a. Ideal Switched Capacitor Model
Charge Pump Efficiency
REQUIV
V+
The overall power efficiency of the charge pump is
affected by four factors:
Vout
R
(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 effective
series resistance (ESR).
EQUIV
+f
1
C1
C2
RL
Figure 2b. Equivalent Output Resistance
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MAX828 MAX829
Capacitor Selection
1
2
C1+
OUT
IN
Vout
C2
3.3 mF*
5
+
+
MAX828
MAX829
In order to maintain the lowest output resistance and
output ripple voltage, it is recommended that low ESR
capacitors be used. Additionally, larger values of C1 will
lower the output resistance and larger values of C2 will
reduce output ripple. (See Equation 3).
Table 1 shows various values of C1 and the corresponding
output resistance values at +25°C. It assumes a 0.1W ESRC1
and 0.5W RSW. Table 2 shows the output voltage ripple for
various values of C2. The VRIPPLE values assume 10mA
output load current and 0.1W ESRC2.
Vin
+
C3
3.3 mF*
RL
C1
3.3 mF*
GND
4
–
3 C1
Table 1. Output Resistance vs. C1 (ESR = 0.1Ω)
C1(µF)
MAX828 ROUT (W)
MAX829 ROUT (W)
0.1
1.7k
580
1
170
61
3.3
55
21
Cascading Devices
10
21
10
47
8.0
5.7
100
6.2
5.1
Two or more MAX828/829’s can be cascaded to increase
output voltage (Figure 4). If the output is lightly loaded, it
will be close to (- 2 x VIN) but will droop at least by ROUT of
the first device multiplied by the IQ of the second. It can be
seen that the output resistance rises rapidly for multiple
cascaded devices.
Figure 3. Test Circuit
Table 2. Output Voltage Ripple vs. C2 (ESR = 0.1W) IOUT
= 10mA
C2(µF)
MAX828 VRIPPLE (mV) MAX829 VRIPPLE (mV)
1
830
290
3.3
250
87
10
83
28
47
17
6.1
100
8.3
2.9
*10 mF (MAX828)
Voltage Inverter
Vin+
3
C1
+
4
2
3
C1
+
MAX828
MAX829
“1”
4
2
MAX828
MAX829
“n”
Input Supply Bypassing
Vout
The VIN input should be capacitively bypassed to reduce
AC impedance and minimize noise effects due to the
switching internal to the device. The recommended
capacitor depends on the configuration of the MAX828/829.
If the device is loaded from OUT to GND it is
recommended that a large value capacitor (at least equal to
C1) be connected from the input to GND. If the device is
loaded from IN to OUT a small (0.1µF) capacitor from IN
to OUT is sufficient.
5
5
1
C2
1
C2
+
+
Vout = –nVin
Figure 4. Cascading MAX828s or MAX829s to
Increase Output Voltage
Paralleling Devices
To reduce the value of ROUT, multiple MAX828/829s can
be connected in parallel (Figure 5). The output resistance
will be reduced by a factor of N where N is the number of
MAX828/829’s. Each device will require it’s own pump
capacitor (C1), but all devices may share one reservoir
capacitor (C2). However, to preserve ripple performance the
value of C2 should be scaled according to the number of
paralleled MAX828/829’s.
Voltage Inverter
The most common application for charge pump devices is
the inverter (Figure 3). This application uses two external
capacitors - C1 and C2 (plus a power supply bypass
capacitor, if necessary). The output is equal to –VIN plus any
voltage drops due to loading. Refer to Table 1 and Table 2
for capacitor selection.
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MAX828 MAX829
R out
out OF SINGLE DEVICE
+ RNUMBER
OF DEVICES
Diode Protection for Heavy Loads
When heavy loads require the OUT pin to sink large
currents being delivered by a positive source, diode
protection may be needed. The OUT pin should not be
allowed to be pulled above ground. This is accomplished by
connecting a Schottky diode (1N5817) as shown in Figure
7.
Vin+
3
C1
+
4
2
3
C1
+
MAX828
MAX829
“1”
4
2
MAX828
MAX829
“n”
...
GND
Vout
5
5
1
MAX828
MAX829
1
Vout = Vin–
C2
+
OUT
Figure 5. Paralleling MAX828s or MAX829s to
Reduce Output Resistance
Layout Considerations
As with any switching power supply circuit good layout
practice is recommended. Mount components as close
together as possible to minimize stray inductance and
capacitance. Also use a large ground plane to minimize
noise leakage into other circuitry.
Another common application of the MAX828/829 is
shown in Figure 6. This circuit performs two functions in
combination. C1 and C2 form the standard inverter circuit
described above. C3 and C4 plus the two diodes form the
voltage doubler circuit. C1 and C3 are the pump capacitors
and C2 and C4 are the reservoir capacitors. Because both
sub–circuits rely on the same switches if either output is
loaded, both will droop toward GND. Make sure that the
total current drawn from both the outputs does not total more
than 40mA.
Vin+
D1, D2 = 1N4148
2
C1
+
4
D1
MAX828
MAX829
5
1
+
C2
D2
+
C3
1
Figure 7. High V– Load Current
Voltage Doubler/Inverter
3
4
+
C4
Vout = Vin–
Vout = (2Vin) –
(VFD1) – (VFD2)
Figure 6. Combined Doubler and Inverter
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MAX828 MAX829
TYPICAL CHARACTERISTICS
80
60
70
OUTPUT RESISTANCE (W )
OUTPUT RESISTANCE (W )
Circuit of Figure 3, Vin = +5 V, C1 = C2 = C3, TA = +25°C, unless otherwise noted.
70
50
40
30
MAX829
MAX828
20
10
40
Vin = 3.3 V
30
20
Vin = 5.0 V
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
–40
5.0
0
25
85
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 8. Output Resistance versus
Supply Voltage
Figure 9. Output Resistance versus
Temperature
40
35
OUTPUT CURRENT (mA)
40
OUTPUT CURRENT (mA)
50
10
0
Vin = 4.75 V, Vout = –4.0 V
30
25
Vin = 3.15 V, Vout = –2.5 V
20
15
10
Vin = 1.9 V, Vout = –1.5 V
35
Vin = 4.75 V, Vout = –4.0 V
30
25
Vin = 3.15 V, Vout = –2.5 V
20
15
10
Vin = 1.9 V, Vout = –1.5 V
5
5
0
0
0
5
10
15
20
25
30
35
0
15
20
25
30
CAPACITANCE (mF)
Figure 11. Output Current versus
Capacitance (MAX829)
Vin = 4.75 V, Vout = –4.0 V
350
10
CAPACITANCE (mF)
450
400
5
Figure 10. Output Current versus
Capacitance (MAX828)
OUTPUT VOLTAGE RIPPLE (mVp–p)
OUTPUT VOLTAGE RIPPLE (mVp–p)
Vin = 1.5 V
60
300
Vin = 3.15 V, Vout = –2.5 V
250
200
Vin = 1.9 V, Vout = –1.5 V
150
100
50
0
35
300
250
Vin = 4.75 V, Vout = –4.0 V
200
Vin = 3.15 V, Vout = –2.5 V
150
Vin = 1.9 V, Vout = –1.5 V
100
50
0
0
5
10
15
20
25
30
35
0
5
10
15
20
25
30
CAPACITANCE (mF)
CAPACITANCE (mF)
Figure 12. Output Voltage Ripple versus
Capacitance (MAX828)
Figure 13. Output Voltage Ripple versus
Capacitance (MAX829)
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35
MAX828 MAX829
TYPICAL CHARACTERISTICS
Circuit of Figure 3, Vin = +5 V, C1 = C2 = C3, TA = +25°C, unless otherwise noted.
14
100
PUMP FREQUENCY (kHz)
SUPPLY CURRENT ( m A)
120
MAX829
80
60
40
MAX828
20
12
Vin = 3.3 V
10
Vin = 1.5 V
8
6
4
2
0
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
–40
25
85
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
Figure 15. Pump Frequency versus
Temperature (MAX828)
0
Vin = 5.0 V
40
–1
OUTPUT VOLTAGE (V)
35
Vin = 3.3 V
30
25
Vin = 1.5 V
20
15
10
Vin = 2.0 V
–2
Vin = 3.3 V
–3
Vin = 5.0 V
–4
–5
5
–6
0
25
85
0
10
20
30
40
TEMPERATURE (°C)
OUTPUT CURRENT (mA)
Figure 16. Pump Frequency versus
Temperature (MAX829)
Figure 17. Output Voltage versus
Output Current
100
Vin = 5.0 V
EFFICIENCY (%)
0
–40
0
Figure 14. Supply Current versus
Supply Voltage
45
PUMP FREQUENCY (kHz)
Vin = 5.0 V
80
Vin = 3.3 V
Vin = 1.5 V
60
40
0
10
20
30
40
OUTPUT CURRENT (mA)
Figure 18. Efficiency versus Output
Current
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50
50
MAX828 MAX829
TAPING FORM
Component Taping Orientation for 5L SOT–23 Devices
USER DIRECTION OF FEED
DEVICE
MARKING
PIN 1
Standard Reel Component Orientation
for TR Suffix Device
(Mark Right Side Up)
Tape & Reel Specifications Table
Package
Tape Width (W)
Pitch (P)
Part Per Full Reel
Diameter
5L SOT–23
8 mm
4 mm
3000
7 inches
MARKING
SOT–23–5
1
2
3
4
MAX828/829
Marking
MAX828SNTR
MAX829SNTR
CA
CB
3
+
4
1
+
2
Date Code
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MAX828 MAX829
PACKAGE DIMENSIONS
SOT–23–5
PLASTIC PACKAGE
CASE TBD
ISSUE TBD
0.75 (1.90)
REFERENCE
.122 (3.10)
.098 (2.50)
.071 (1.80)
.059 (1.50)
.020 (0.50)
.012 (0.30)
.037 (0.95)
REFERENCE
.122 (3.10)
.106 (2.70)
.057 (1.45)
.035 (0.90)
10 ° MAX.
.006 (0.15)
.000 (0.00)
.010 (0.25)
.004 (0.09)
.022 (0.55)
.008 (0.20)
NOTE: SOT–23–5 is equivalent to EIAJ–SC74A
Dimensions: inches (mm)
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MAX828 MAX829
Notes
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MAX828 MAX829
Notes
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MAX828 MAX829
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MAX828/D
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