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19-1792; Rev 0; 9/00
SC70 Inverting Charge Pumps with Shutdown
General Description
The MAX1852/MAX1853 monolithic, CMOS chargepump voltage inverters in the ultra-small SC70 package feature a low 15 output resistance, permitting loads up to 30mA with maximum efficiency. The MAX1852/ MAX1853 are available with operating frequencies of 50kHz and 200kHz, respectively, allowing optimization of supply current or external component size. Small external components and micropower shutdown mode make these devices ideal for both battery-powered and board-level voltage conversion applications. Oscillator control circuitry and four power-MOSFET switches are included on-chip. Applications include generating a negative supply from a +5V or +3.3V logic supply to power analog circuitry. Both versions come in a 6-pin SC70 package that is 40% smaller than a SOT23. o 30mA Output Current o Low 15 Output Resistance o 68A Supply Current (MAX1852) o Requires Only Two 0.68F Capacitors (MAX1853) o +2.5V to +5.5V Input Voltage Range o 0.1A Logic-Controlled Shutdown o Two Switching Frequencies 50kHz (MAX1852) 200kHz (MAX1853) o Slew-Rate Limited to Reduce EMI o Ultra-Small 6-Pin SC70 Package
Features
MAX1852/MAX1853
Applications
Negative Supply from +5V or +3.3V Logic Supplies Small LCD Panels GaAsFET Bias Supplies Handy-Terminals, PDAs Battery-Operated Equipment
PART MAX1852EXT MAX1853EXT TEMP. RANGE -40C to +85C -40C to +85C PINPACKAGE 6 SC70 6 SC70 TOP MARK AAL AAM
Ordering Information
Typical Operating Circuit
0.68F
Pin Configuration
TOP VIEW
INPUT 2.5V TO 5.5V
C1+ IN
C1OUT
NEGATIVE OUTPUT -1 VIN 30mA 0.68F
OUT
1
6
C1+
MAX1853
ON OFF SHDN GND
GND
2
MAX1852 MAX1853
5 C1-
SHDN
3
4
IN
SC70-6
________________________________________________________________ Maxim Integrated Products
1
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SC70 Inverting Charge Pumps with Shutdown MAX1852/MAX1853
ABSOLUTE MAXIMUM RATINGS
IN to GND .................................................................-0.3V to +6V C1+, SHDN to GND .....................................-0.3V to (VIN + 0.3V) C1- to GND...............................................(VOUT - 0.3V) to +0.3V OUT to GND .............................................................+0.3V to -6V OUT Short-Circuit to GND ..............................................1 minute Continuous Power Dissipation (TA = +70C) 6-Pin SC70 (derate 3.1mW/C above +70C) .............245mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1)
PARAMETER Supply Voltage Range MAX1852 Quiescent Supply Current MAX1853 Shutdown Supply Current SHDN = GND MAX1852 Oscillator Frequency MAX1853 Voltage Conversion Efficiency Output Resistance (Note 2) Output Current SHDN Input Logic High SHDN Input Logic Low SHDN Bias Current Wake-Up Time From Shutdown IOUT = 0 IOUT = 10mA Continuous, long-term +2.5V VIN +5.5V +2.5V VIN +5.5V SHDN = GND or IN IOUT = 5mA TA = +25C TA = +85C MAX1852 MAX1853 -100 1 10 260 112 0.7 x VIN 0.3 x VIN 100 TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C TA = +25C TA = +85C TA = +25C TA = -40C to +85C TA = +25C TA = -40C to +85C 32 25 130 110 99 99.9 15 30 40 30 200 0.002 0.01 50 68 78 270 310 % mARMS V V nA s kHz 165 CONDITIONS MIN 2.5 75 TYP MAX 5.5 130 150 320 350 0.5 A A UNITS V
Note 1: All devices are 100% production tested at TA = +25C. All temperature limits are guaranteed by design. Note 2: Output resistance is guaranteed with capacitor ESR of 0.3 or less.
2
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SC70 Inverting Charge Pumps with Shutdown MAX1852/MAX1853
Typical Operating Characteristics
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25C, unless otherwise noted.)
MAX1852 OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1852/3 toc01
MAX1853 OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1852/3 toc02
MAX1852 EFFICIENCY vs. LOAD CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 VIN = +5V VIN = +3.3V VIN = +2.5V
MAX1852/3 toc03
-2.0 -2.5 VIN = +3.3V OUTPUT VOLTAGE (V) -3.0 -3.5 -4.0 -4.5 -5.0 -5.5 0 5 10 15 20 25 VIN = +5V
-2.0 -2.5 VIN = +3.3V OUTPUT VOLTAGE (V) -3.0 -3.5 -4.0 -4.5 -5.0 -5.5 VIN = +5V
100
10 0 0 5 10 15 20 25 30 0 5 10 15 20 25 30 LOAD CURRENT (mA) LOAD CURRENT (mA)
30
LOAD CURRENT (mA)
MAX1853 EFFICIENCY vs. LOAD CURRENT
MAX1852/3 toc04
OUTPUT RESISTANCE vs. INPUT VOLTAGE
22 OUTPUT RESISTANCE () 21 20 19 18 17 16 15 14 13 MAX1852 MAX1853
MAX1852/3 toc05
NO-LOAD SUPPLY CURRENT vs. SUPPLY VOLTAGE
180 160 SUPPLY CURRENT (A) 140 120 100 80 60 40 20 0 MAX1852 MAX1853
MAX1852/3 toc06
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 5 10 15 20 25 VIN = +5V VIN = +3.3V VIN = +2.5V
23
200
30
2.5
3.0
3.5
4.0
4.5
5.0
5.5
0
1
2
3
4
5
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
SUPPLY VOLTAGE (V)
SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX1852/3 toc07
MAX1852 OUTPUT RESISTANCE vs. TEMPERATURE
MAX1852/3 toc08
MAX1853 OUTPUT RESISTANCE vs. TEMPERATURE
26 OUTPUT RESISTANCE () 24 22 20 18 16 14 12 VIN = +5V VIN = +3.3V VIN = +2.5V
MAX1852/3 toc09
8 7 SUPPLY CURRENT (nA) 6 5 4 3 2 1 0 -40 -15 10 35 60
28 26 OUTPUT RESISTANCE () 24 VIN = +2.5V 22 20 18 16 14 12 -40 -15 10 35 60 VIN = +5V VIN = +3.3V
28
85
85
-40
-15
10
35
60
85
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
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SC70 Inverting Charge Pumps with Shutdown MAX1852/MAX1853
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25C, unless otherwise noted.)
MAX1852 CHARGE-PUMP FREQUENCY vs. TEMPERATURE
MAX1852/3 toc10
MAX1853 CHARGE-PUMP FREQUENCY vs. TEMPERATURE
MAX1852/3 toc11
CHARGE-PUMP FREQUENCY vs. INPUT VOLTAGE
270 220 170 120 70 20 MAX1852 MAX1853
MAX1852/3 toc12
60 59 58 FREQUENCY (kHz) 57 56 55 54 53 52 51 50 -40 -20 0 20 40 60 80 TEMPERATURE (C)
230 225 FREQUENCY (kHz) 220 215 210 205 200 -40 -20 0 20 40 60 80 TEMPERATURE (C)
FREQUENCY (kHz)
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
INPUT VOLTAGE (V)
MAX1852 AND MAX1853 OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1852/3 toc13
OUTPUT VOLTAGE RIPPLE vs. CAPACITANCE
MAX1852/3 toc14
MAX1852 OUTPUT NOISE AND RIPPLE
C1 = C2 = 4.7F
MAX1852/3 toc15
-2.0 -2.5 OUTPUT VOLTAGE (V) -3.0 -3.5 -4.0 -4.5 -5.0 -5.5 2.0 2.5 3.0 3.5 4.0
ILOAD = 10mA
350 OUTPUT VOLTAGE RIPPLE (mV) 300 250 200 150 100 MAX1853 50 0 MAX1852 C1 = C2 ILOAD = 10mA
VOUT 20mV/div
4.5
5.0
5.5
0.2 0.7 1.2 1.7 2.2 2.7 3.2 3.7 4.2 4.7 CAPACITANCE (F)
INPUT VOLTAGE (V)
10s/div ILOAD = 10mA, AC-COUPLED
MAX1853 OUTPUT NOISE AND RIPPLE
C1 = C2 = 1F
MAX1852/3 toc16
MAX1852 STARTUP FROM SHUTDOWN
MAX1852/3 toc17
MAX1853 STARTUP FROM SHUTDOWN
MAX1852/3 toc18
SHDN
SHDN
VOUT 20mV/div
0 0
2V/div
0 0 VOUT
2V/div
VOUT
2s/div ILOAD = 10mA, AC-COUPLED
100s/div
40s/div
4
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SC70 Inverting Charge Pumps with Shutdown
Pin Description
C1
MAX1852/MAX1853
PIN
NAME OUT GND SHDN
FUNCTION Inverting Charge-Pump Output Ground Shutdown Input. Drive this pin high for normal operation; drive it low for shutdown mode. Power-Supply Voltage Input. Input range is +2.5V to +5.5V. Negative Terminal of the Flying Capacitor Positive Terminal of the Flying Capacitor
INPUT 2.5V TO 5.5V C3 4 6 C1+ IN 5 C1OUT 1 RL NEGATIVE OUTPUT -1 VIN C2
1
2 3
ON OFF
3
MAX1852 MAX1853
SHDN GND 2
4 5 6
IN C1C1+
TE: (
Figure 1. Typical Application Circuit
Detailed Description
The MAX1852/MAX1853 charge pumps invert the voltage applied to their input. For highest performance use low equivalent series resistance (ESR) capacitors (e.g., ceramic). During the first half-cycle, switches S2 and S4 open, switches S1 and S3 close, and capacitor C1 charges to the voltage at IN (Figure 2). During the second halfcycle, S1 and S3 open, S2 and S4 close, and C1 is level shifted downward by VIN volts. This connects C1 in parallel with the reservoir capacitor C2. If the voltage across C2 is smaller than the voltage across C1, charge flows from C1 to C2 until the voltage across C2 reaches -VIN. The actual voltage at the output is more positive than -VIN since switches S1-S4 have resistance and the load drains charge from C2.
resistances (typically 6 at VIN = +5V). The typical output impedance is more accurately determined from the Typical Operating Characteristics.
Shutdown
The MAX1852/MAX1853 have a logic-controlled shutdown input. Driving SHDN low places the devices in a low-power shutdown mode. The charge-pump switching halts, supply current is reduced to 2nA. Driving SHDN high will restart the charge pump. The switching frequency and capacitor values determine how soon the device will reach 90% of the input voltage.
Applications Information
Capacitor Selection
The charge-pump output resistance is a function of the ESR of C1 and C2. To maintain the lowest output resistance, use capacitors with low ESR. (See Table 1 for a list of recommended manufacturers.) Tables 2 and 3 suggest capacitor values for minimizing output resistance or capacitor size. Flying Capacitor (C1) Increasing the flying capacitor's value reduces the output resistance. Above a certain point, increasing C1's capacitance has negligible effect because the output resistance is then dominated by internal switch resistance and capacitor ESR. Output Capacitor (C2) Increasing the output capacitor's value reduces the output ripple voltage. Decreasing its ESR reduces both output resistance and ripple. Lower capacitance values can be used with light loads if higher output ripple can be tolerated. Use the following equation to calculate the peak-to-peak ripple:
5
Efficiency Considerations
The efficiency of the MAX1852/MAX1853 is dominated by their quiescent supply current (IQ) at low output current and by their output impedance (ROUT) at higher output current; it is given by: IOUT IOUT x ROUT 1 - VIN IOUT + IQ where the output impedance is roughly approximated by: 1 ROUT + 2RSW + 4ESRC1 + ESRC2 fOSC x C1
(
)
The first term is the effective resistance of an ideal switched-capacitor circuit (Figures 3a and 3b), and RSW is the sum of the charge pump's internal switch
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SC70 Inverting Charge Pumps with Shutdown MAX1852/MAX1853
S1 IN C1 S2 V+ REQUIV = 1 fOSC C1 C2 RL REQUIV VOUT
S3
S4
C2 VOUT = -(VIN)
Figure 3b. Equivalent Circuit
Paralleling Devices
Figure 2. Ideal Voltage Inverter
fOSC V+ VOUT C2 RL
Paralleling multiple MAX1852/MAX1853s reduces the output resistance. Each device requires its own pump capacitor (C1), but the reservoir capacitor (C2) serves all devices (Figure 5). Increase C2's value by a factor of n, where n is the number of parallel devices. Figure 5 shows the equation for calculating output resistance.
C1
Combined Doubler/Inverter
In the circuit of Figure 6, capacitors C1 and C2 form the inverter, while C3 and C4 form the doubler. C1 and C3 are the pump capacitors; C2 and C4 are the reservoir capacitors. Because both the inverter and doubler use part of the charge-pump circuit, loading either output causes both outputs to decline toward GND. Make sure the sum of the currents drawn from the two outputs does not exceed 30mA.
Figure 3a. Switched-Capacitor Model
VRIPPLE =
IOUT + 2 x IOUT x ESRC2 2(fOSC )C2
Input Bypass Capacitor (C3) If necessary, bypass the incoming supply to reduce its AC impedance and the impact of the MAX1852/ MAX1853s' switching noise. A bypass capacitor with a value equal to that of C1 is recommended.
Heavy Load Connected to a Positive Supply
Under heavy loads, where a higher supply is sourcing current into OUT, the OUT supply must not be pulled above ground. Applications that sink heavy current into OUT require a Schottky diode (1N5817) between GND and OUT, with the anode connected to OUT (Figure 7).
Voltage Inverter
The most common application for these devices is a charge-pump voltage inverter (Figure 1). This application requires only two external components--capacitors C1 and C2--plus a bypass capacitor, if necessary. Refer to the Capacitor Selection section for suggested capacitor types.
Layout and Grounding
Good layout is important, primarily for good noise performance. To ensure good layout, mount all components as close together as possible, keep traces short to minimize parasitic inductance and capacitance, and use a ground plane.
Cascading Devices
Two devices can be cascaded to produce an even larger negative voltage (Figure 4). The unloaded output voltage is normally -2 VIN, but this is reduced slightly by the output resistance of the first device multiplied by the quiescent current of the second. When cascading more than two devices, the output resistance rises significantly. For applications requiring larger negative voltages, see the MAX865 and MAX868 data sheets.
6
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SC70 Inverting Charge Pumps with Shutdown MAX1852/MAX1853
Table 1. Low-ESR Capacitor Manufacturers
PRODUCTION METHOD Surface-Mount Tantalum Surface-Mount Ceramic MANUFACTURER AVX Matsuo Sprague AVX Matsuo SERIES TPS series 267 series 593D, 595D series X7R X7R PHONE 803-946-0690 714-969-2491 603-224-1961 803-946-0690 714-969-2491 FAX 803-626-3123 714-960-6492 603-224-1430 803-626-3123 714-960-6492
Table 2. Capacitor Selection to Minimize Output Resistance
PART MAX1852 MAX1853 FREQUENCY (kHz) 50 200 CAPACITOR (F) 4.7 1 TYPICAL ROUT () 15 15
Table 3. Capacitor Selection to Minimize Capacitor Size
PART MAX1852 MAX1853 FREQUENCY (kHz) 50 200 CAPACITOR (F) 3.3 0.68 TYPICAL ROUT () 20 20
...
4 5 C1 2 6 3 SHDN MAX1852 MAX1853 1 C1 +VIN 5 2 6 MAX1852 MAX1853 1 3 VOUT C2 C1 4
SHDN 3 5 2 6 MAX1852 MAX1853 1 C2 D2 VOUT = -nVIN C3 C4 VOUT = (2VIN) (VFD1) - (VFD2) 4 +VIN D1, D2 = 1N4148
D1 VOUT = -VIN
...
C2
Figure 4. Cascading MAX1852/MAX1853s to Increase Output Voltage
Figure 6. Combined Doubler and Inverter
+VIN 4 5 C1 2 6 3 SHDN ROUT OF SINGLE DEVICE ROUT = NUMBER OF DEVICES MAX1852 MAX1853 1
...
4 5 MAX1852 MAX1853 1 3 VOUT = -VIN C2 VOUT MAX1852 MAX1853 OUT 1 GND 2 V+ RL
C1
2 6
...
Figure 7. Heavy Load Connected to a Positive Supply
Chip Information
TRANSISTOR COUNT: 252
7
Figure 5. Paralleling MAX1852/MAX1853s to Reduce Output Resistance
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SC70 Inverting Charge Pumps with Shutdown MAX1852/MAX1853
________________________________________________________Package Information
SC70, 6L.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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