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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 (3.3F 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 A (MAX828) and 115 A (MAX829). The MAX828 and MAX829 are available in a SOT-23 5 lead surface mount package. Features
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SOT-23-5 SN SUFFIX CASE TBD PRELIMINARY INFORMATION
Charge Pump in SOT-23 5 Lead Package >95% Voltage Conversion Efficiency Voltage Inversion and/or Doubling Low 50 A (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: -40C to +85C
PIN CONFIGURATION (Top View)
1 2 3 4 GND 5 C+
OUT Vin C-
Typical Applications LCD Panel Bias Cellular Phones Pagers PDAs, Portable Dataloggers Battery-Powered Devices
TYPICAL OPERATING CIRCUIT
Voltage Inverter C+ + C- MAX828 MAX829 C1 Vin INPUT MAX829SNTR
SOT-23-5*
NOTE: *SOT-23-5 is equivalent to EIAJ-SC74A
ORDERING INFORMATION
Device MAX828SNTR Package SOT-23-5 SOT-23-5 Shipping 3000 Tape/Reel 3000 Tape/Reel
OUT GND + C2
V- OUTPUT
(c) Semiconductor Components Industries, LLC, 1999
1
February, 2000 - Rev. 0
Publication Order Number: MAX828/D
MAX828 MAX829
PIN DESCRIPTION
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1 2 3 4 4 OUT VIN C- Inverting charge pump output Positive power supply input Commutation capacitor negative terminal Ground GND C+ Commutation capacitor positive terminal
Pin No.
Symbol
Description
ABSOLUTE MAXIMUM RATINGS*
Symbol
Parameter
Value
Unit V V mA
Input Voltage (VIN to GND) Output Voltage (OUT to GND) Current at OUT Pin Short-Circuit Duration - OUT to GND TA PD Tstg Tsol Operating Temperature Range Power Dissipation (TA 70C) SOT-23-5 Derate by 4mW/C for TA > 70C Storage Temperature Range Lead Temperature (Soldering, 10 Seconds)
+6.0, - 0.3 -6.0, +0.3 50 Indefinite -40 to +85 240 -65 to +150 +300
C mW C C
* Maximum Ratings are those values beyond which damage to the device may occur.
ELECTRICAL CHARACTERISTICS (TA = 0C to +85C, VIN = +5V, C1 = C2 = 10F (MAX828), C1 = C2 = 3.3F (MAX829), unless otherwise noted. Typical values are at TA = 25C.)
Symbol IDD Supply Current (TA = 25C) MAX828 MAX829 Supply Voltage Range (RLOAD = 10kW) Oscillator Frequency (TA = 25C) MAX828 MAX829 Power Efficiency ILOAD = 3mA, TA = 25C Voltage Conversion Efficiency (RLOAD = Output Resistance (Note 1.) IOUT = 5mA, TA = 25C TA = 0C to +85C Characteristic Min -- -- -- 8.4 24.5 -- 95 -- -- Typ 50 115 -- 12 35 96 99.9 25 -- 50 65 Max 90 260 5.5 15.6 45.5 % -- %
W
Unit A
V+ FOSC
V kHz
PEFF VEFF ROUT
R)
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 = -40C to +85C, VIN = +5V, C1 = C2 = 10F (MAX828), C1 = C2 = 3.3F (MAX829), unless otherwise noted. Typical values are at TA = 25C.) (Note 2.)
Symbol IDD Supply Current MAX828 MAX829 Supply Voltage Range (RLOAD = 10kW) Oscillator Frequency MAX828 MAX829 Characteristic Min -- -- 1.5 6.0 19 -- Typ -- -- -- -- -- -- Max 115 325 5.5 20 54.3 65
W
Unit A
Vin FOSC
V kHz
ROUT Output Resistance (IOUT = 5mA) 2. All -40C to +85C specifications are guaranteed by design.
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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 IN C1 S2
(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.
P LOSS(2,3,4) 1 (f OSC )C1
+ IOUT
2
R
OUT
^ IOUT
2
) 8RSWITCH ) 4ESRC1 ) ESRC2
Equation 1.
MAX828/829
C2 S3 S4 Vout = -(Vin)
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.
P LOSS(4)
+
(V
(0.5)(C1)( V 2 IN
2
RIPPLE
* 2VOUT VRIPPLE)
* VOUT ) ) (0.5)(C2)
2
f
OSC
Equation 2. Figure 1. Ideal Switched Capacitor Charge Pump V RIPPLE
APPLICATIONS INFORMATION
Output Voltage Considerations
+ (f
OUT )(C2) OSC
I
) 2(IOUT)(ESRC2)
Equation 3.
f V+ Vout RL
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 +25C and VIN = +5V. VOUT is approximately - 5V at light loads, and droops according to the equation below: VDROP = IOUT x ROUT VOUT = - (VIN - VDROP)
Charge Pump Efficiency
C1
C2
Figure 2a. Ideal Switched Capacitor Model
REQUIV V+ R Vout
The overall power 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 effective series resistance (ESR).
EQUIV
+f
1 C1
C2
RL
Figure 2b. Equivalent Output Resistance
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MAX828 MAX829
Capacitor Selection
3.3 mF* C3 + Vin
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 +25C. 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.
Table 1. Output Resistance vs. C1 (ESR = 0.1) C1(F) 0.1 1 3.3 10 47 100 MAX828 ROUT (W) 1.7k 170 55 21 8.0 6.2 MAX829 ROUT (W) 580 61 21 10 5.7 5.1
1
OUT MAX828 MAX829
C1+
5 +
C2 3.3 mF* + C1 3.3 mF* RL
Vout
2
IN
GND - 3 C1 Voltage Inverter
4
*10 mF (MAX828)
Figure 3. Test Circuit Cascading Devices
Table 2. Output Voltage Ripple vs. C2 (ESR = 0.1W) IOUT = 10mA C2(F) 1 3.3 10 47 100 MAX828 VRIPPLE (mV) MAX829 VRIPPLE (mV) 830 250 83 17 8.3 290 87 28 6.1 2.9
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.
Vin+ 3 C1 + 4 MAX828 MAX829 "1" 2 3 C1 + 4 MAX828 MAX829 "n" Vout 5 1 C2 + Vout = -nVin 5 1 C2 + 2
Input Supply Bypassing
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 (0.1F) capacitor from IN to OUT is sufficient.
Voltage Inverter
Figure 4. Cascading MAX828s or MAX829s to Increase Output Voltage Paralleling Devices
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.
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.
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MAX828 MAX829
R out out OF SINGLE DEVICE + RNUMBER OF DEVICES
Diode Protection for Heavy Loads
Vin+
3 C1 + 4 MAX828 MAX829 "1"
2
3 C1 + 4 MAX828 MAX829 "n" ...
2
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.
GND
4
Vout 5 1 5 Vout = Vin- 1 C2
MAX828 MAX829
+
OUT
1
Figure 5. Paralleling MAX828s or MAX829s to Reduce Output Resistance Voltage Doubler/Inverter
Figure 7. High V- Load Current Layout Considerations
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+ 3 C1 + 4 MAX828 MAX829 D1 2 D1, D2 = 1N4148
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.
5
1 + D2 + C3 +
C2
Vout = Vin-
C4
Vout = (2Vin) - (VFD1) - (VFD2)
Figure 6. Combined Doubler and Inverter
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MAX828 MAX829 TYPICAL CHARACTERISTICS
Circuit of Figure 3, Vin = +5 V, C1 = C2 = C3, TA = +25C, unless otherwise noted.
70 OUTPUT RESISTANCE (W ) OUTPUT RESISTANCE (W ) 60 50 40 30 20 10 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) MAX829 MAX828 80 70 Vin = 1.5 V 60 50 40 30 20 10 0 -40 0 25 85 TEMPERATURE (C) Vin = 3.3 V Vin = 5.0 V
Figure 8. Output Resistance versus Supply Voltage
40 OUTPUT CURRENT (mA) Vin = 4.75 V, Vout = -4.0 V OUTPUT CURRENT (mA) 35 30 25 Vin = 3.15 V, Vout = -2.5 V 20 15 10 Vin = 1.9 V, Vout = -1.5 V 5 0 0 5 10 15 20 25 30 35 CAPACITANCE (mF) 40 35 30 25 20 15 10 5 0 0
Figure 9. Output Resistance versus Temperature
Vin = 4.75 V, Vout = -4.0 V
Vin = 3.15 V, Vout = -2.5 V
Vin = 1.9 V, Vout = -1.5 V
5
10
15
20
25
30
35
CAPACITANCE (mF)
Figure 10. Output Current versus Capacitance (MAX828)
OUTPUT VOLTAGE RIPPLE (mVp-p) OUTPUT VOLTAGE RIPPLE (mVp-p) 450 400 350 300 250 200 150 100 50 0 0 5 10 15 20 25 30 35 CAPACITANCE (mF) Vin = 4.75 V, Vout = -4.0 V 300 250 200
Figure 11. Output Current versus Capacitance (MAX829)
Vin = 4.75 V, Vout = -4.0 V Vin = 3.15 V, Vout = -2.5 V
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 CAPACITANCE (mF)
Vin = 1.9 V, Vout = -1.5 V
Figure 12. Output Voltage Ripple versus Capacitance (MAX828)
Figure 13. Output Voltage Ripple versus Capacitance (MAX829)
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MAX828 MAX829 TYPICAL CHARACTERISTICS
Circuit of Figure 3, Vin = +5 V, C1 = C2 = C3, TA = +25C, unless otherwise noted.
120 PUMP FREQUENCY (kHz) 100 MAX829 80 60 40 MAX828 20 0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 14 12 10 8 6 4 2 0 -40 0 25 85 TEMPERATURE (C) Vin = 3.3 V Vin = 1.5 V Vin = 5.0 V
SUPPLY CURRENT ( m A)
Figure 14. Supply Current versus Supply Voltage
45 40 PUMP FREQUENCY (kHz) 35 30 25 20 15 10 5 0 -40 0 25 85 Vin = 3.3 V Vin = 1.5 V Vin = 5.0 V -1 OUTPUT VOLTAGE (V) -2 -3 0
Figure 15. Pump Frequency versus Temperature (MAX828)
Vin = 2.0 V
Vin = 3.3 V Vin = 5.0 V
-4 -5 -6 0 10 20 30 40 50
TEMPERATURE (C)
OUTPUT CURRENT (mA)
Figure 16. Pump Frequency versus Temperature (MAX829)
100
Figure 17. Output Voltage versus Output Current
Vin = 5.0 V EFFICIENCY (%) 80 Vin = 3.3 V Vin = 1.5 V 60
40 0 10 20 30 40 50 OUTPUT CURRENT (mA)
Figure 18. Efficiency versus Output Current
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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 5L SOT-23 Tape Width (W) 8 mm Pitch (P) 4 mm Part Per Full Reel 3000 Diameter 7 inches
MARKING
SOT-23-5
1
2
3
4
MAX828/829 MAX828SNTR MAX829SNTR
Marking CA CB Date Code
1
+
2
3
+
4
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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) .006 (0.15) .000 (0.00) NOTE: SOT-23-5 is equivalent to EIAJ-SC74A
10 MAX.
.010 (0.25) .004 (0.09) .022 (0.55) .008 (0.20) 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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