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19-1499; Rev 3; 12/08
60mA, SOT23 Inverting Charge Pump with Shutdown
General Description
The MAX1697 ultra-small, monolithic, CMOS chargepump voltage inverter accepts an input voltage ranging from +1.25V to +5.5V. This device features an ultra-low 12 output resistance, permitting loads of up to 60mA with maximum efficiency. The MAX1697 is available with operating frequencies of 12kHz, 35kHz, 125kHz, or 250kHz, allowing optimization of supply current or external component size. Its small external components and micropower shutdown mode make this device 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. All versions come in a 6-pin SOT23 package and deliver 60mA. For applications with lower current requirements, the MAX1719/MAX1720/MAX1721 are pin-compatible SOT23 charge pumps that supply up to 25mA. 60mA Output Current Low 12 Output Resistance 150A Supply Current (MAX1697R) Requires Only Two 1F Capacitors (MAX1697U) Start-Up Current Limited +1.25V to +5.5V Input Voltage Range Slew-Rate Limited to Reduce EMI
Features
MAX1697
Ordering Information
PART MAX1697_EUT-T TEMP RANGE -40C to +85C PIN-PACKAGE 6 SOT23
Note 1: The MAX1697 requires special solder temperature profile described in the Absolute Maximum Ratings section. Note 2: The MAX1697 is available with four different operating frequencies. Choose the desired frequency from the table below and insert the suffix in the blank above to complete the part number.
PART NO. SUFFIX R S T U FREQUENCY (kHz) 12 35 125 250 TOP MARK -T AABV AABW AABX AABY +T AABV AABW AABX AABY #T ACBT ACCK ACCL ACCM
Applications
Negative Supply from +5V or +3.3V Logic Supplies Small LCD Panels GaAsFET Bias Supplies Handy-Terminals, PDAs Battery-Operated Equipment
Note 3: MAX1697 is available in different package material. Add the following suffix to the part number when ordering: -T = Denotes a package containing lead(Pb). +T = Denotes a lead(Pb)-free/RoHS-compliant package. #T = Denotes an RoHS-compliant device that may include lead(Pb) that is exempt under the RoHS requirements.
Typical Operating Circuit
1F
Pin Configuration
TOP VIEW
+ OUT 1 6 C1+
INPUT 1.5V to 5.5V
C1+ IN
C1OUT
NEGATIVE OUTPUT -1 VIN 60mA 1F
IN
2
MAX1697
5
SHDN
MAX1697U
ON OFF SHDN GND
C1-
3
4
GND
SOT23 Note 4: Leaded and lead-free top marks are identical. Per Maxim guideline, the pin 1 indicator for leaded package is a `*' and the lead-free package is a `+'. 1
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
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 Output Current............................................................90mA OUT Short-Circuit to GND .............................................Indefinite Note 5: Note 6: Continuous Power Dissipation (TA = +70C) 6-Pin SOT23 (derate 14mW/C above +70C) (Note 5)...1.1W Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C Storage Temperature Range .............................-65C to +150C Lead Temperature ..........................................................(Note 6)
Thermal properties are specified with product mounted on the PC board with one square-inch of copper area and still air. This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board level solder attach and rework. Maxim recommends the use of the solder profiles recommended in the industry standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and Convection reflow processes. Preheating, per this standard, is required. Hand or wave soldering is not recommended.
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 = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MAX1697R/S, RL = 5k Supply Voltage Range MAX1697T/U, RL = 5k TA = +25C TA = 0C to +85C TA = +25C TA = 0C to +85C MAX1697R Quiescent Supply Current (Note 9) TA = +25C MAX1697S MAX1697T MAX1697U Shutdown Supply Current Short-Circuit Current SHDN = GND TA = +25C TA = +85C MAX1697R Oscillator Frequency TA = +25C MAX1697S MAX1697T MAX1697U Voltage Conversion Efficiency Output Resistance (Note 7) OUT to GND Shutdown Resistance SHDN Input Logic High SHDN Input Logic Low SHDN Bias Current IOUT = 0, TA = +25C IOUT = 60mA TA = +25C TA = 0C to +85C 3 2.0 VIN - 0.2 0.6 0.2 TA = +25C TA = +85C -100 0.05 10 +100 7 20 70 140 99 MIN 1.25 1.5 1.4 1.5 150 350 950 1800 0.002 0.03 170 12 35 125 250 99.9 12 25 33 8 17 50 180 360 % V V nA kHz TYP MAX 5.5 5.5 5.5 5.5 300 650 1700 3400 1 A mA A V UNITS
Output shorted to ground, TA = +25C
SHDN = GND, OUT is internally pulled to GND in shutdown 2.5V VIN 5.5V VIN(MIN) VIN 2.5V 2.5V VIN 5.5V VIN(MIN) VIN 2.5V SHDN = GND or IN
2
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60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) PARAMETER CONDITIONS MAX1697R Wake-Up Time from Shutdown IOUT = 15mA MAX1697S MAX1697T MAX1697U THERMAL SHUTDOWN Trip Temperature Hysteresis Temperature increasing 150 15 C C MIN TYP 1200 600 100 70 s MAX UNITS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = -40C to +85C, unless otherwise noted.) (Note 8) PARAMETER Supply Voltage Range Output Current Quiescent Current (Note 9) RL = 5k Continuous, long-term MAX1697R MAX1697S MAX1697T MAX1697U MAX1697R Oscillator Frequency MAX1697S MAX1697T MAX1697U Output Resistance (Note 7) OUT to GND Shutdown Resistance SHDN Input Logic High SHDN Input Logic Low IOUT = 60mA SHDN = GND, OUT is internally pulled to GND in shutdown 2.5V VIN 5.5V VIN(MIN) VIN 2.5V 2.5V VIN 5.5V VIN(MIN) VIN 2.5V 2.1 VIN - 0.2 0.6 0.2 6 16 60 120 CONDITIONS MAX1697R/S MAX1697T/U MIN 1.5 1.6 MAX 5.5 5.5 60 350 750 1800 3600 21 60 200 400 33 8 V V kHz A UNITS V mARMS
Note 7: Output resistance is guaranteed with capacitor ESR of 0.3 or less. Note 8: All specifications from -40C to +85C are guaranteed by design, not production tested. Note 9: The MAX1697 may draw high supply current during startup, up to the minimum operating supply voltage. To guarantee proper startup, the input supply must be capable of delivering 90mA more than the maximum load current.
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3
60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
Typical Operating Characteristics
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25C, unless otherwise noted.) MAX1697T MAX1697S MAX1697R OUTPUT VOLTAGE OUTPUT VOLTAGE OUTPUT VOLTAGE vs. OUTPUT CURRENT vs. OUTPUT CURRENT vs. OUTPUT CURRENT
MAX1697 TOC01 MAX1697 TOC02
-0.5 -1.0 OUTPUT VOLTAGE (V) -1.5 -2.0 -2.5 -3.0 -3.5 -4.0 -4.5 -5.0 0 10 20 30 40 50 60 70 VIN = +5V VIN = +3.3V VIN = +2V
-0.5 -1.0 OUTPUT VOLTAGE (V) -1.5 -2.0 -2.5 -3.0 -3.5 -4.0 -4.5 -5.0
VIN = +2V
-0.5 -1.0 OUTPUT VOLTAGE (V) -1.5 -2.0 -2.5 -3.0 -3.5 -4.0 -4.5 -5.0 VIN = +5V VIN = +3.3V VIN = +2V
VIN = +3.3V
VIN = +5V
80
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
MAX1697U OUTPUT VOLTAGE vs. OUTPUT CURRENT
MAX1697 TOC04
MAX1697R EFFICIENCY vs. OUTPUT CURRENT
MAX1697 TOC05
MAX1697S EFFICIENCY vs. OUTPUT CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 VIN = +2V VIN = +3.3V VIN = +5V
MAX1697 TOC06
0 -0.5 -1.0 OUTPUT VOLTAGE (V) -1.5 -2.0 -2.5 -3.0 -3.5 -4.0 -4.5 -5.0 0 10 20 30 40 50 60 70 VIN = +5V VIN = +3.3V VIN = +2V
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 VIN = +2V VIN = +3.3V VIN = +5V
100
80
0
10
20
30
40
50
60
70
80
0
10
20
30
40
50
60
70
80
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
MAX1697T EFFICIENCY vs. OUTPUT CURRENT
MAX1697 TOC07
MAX1697U EFFICIENCY vs. OUTPUT CURRENT
90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 VIN = +2V VIN = +3.3V VIN = +5V
MAX1697 TOC08
MAX1697R/S/T/U OUTPUT IMPEDANCE vs. INPUT VOLTAGE
MAX1697 TOC09
100 90 80 EFFICIENCY (%) 70 60 50 40 30 20 10 0 0 10 20 30 40 50 60 70 VIN = +2V VIN = +3.3V VIN = +5V
100
30 25 OUTPUT IMPEDANCE () 20 15 10 5 0
80
0
10
20
30
40
50
60
70
80
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
INPUT VOLTAGE (V)
4
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MAX1697 TOC03
0
0
0
60mA, SOT23 Inverting Charge Pump with Shutdown
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1697 TOC10
MAX1697
MAX1697R/S/T/U SHUTDOWN SUPPLY CURRENT vs. TEMPERATURE
MAX1697 TOC11
MAX1697R OUTPUT RESISTANCE vs. TEMPERATURE
30 OUTPUT RESISTANCE () 25 VIN = +2V 20 15 10 5 0 VIN = +3.3V VIN = +5V
MAX1697 TOC12
2.5 MAX1697U
35 30 SUPPLY CURRENT (nA) 25 20 15 10 5 0 VIN = +3.3V VIN = +2V VIN = +5V
35 VIN = +1.5V
2.0 SUPPLY CURRENT (mA)
1.5 MAX1697T 1.0 MAX1697S 0.5 MAX1697R
0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 INPUT VOLTAGE (V)
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (C)
TEMPERATURE (C)
MAX1697S OUTPUT RESISTANCE vs. TEMPERATURE
MAX1697 TOC13
MAX1697T OUTPUT RESISTANCE vs. TEMPERATURE
MAX1697 TOC14
MAX1697U OUTPUT RESISTANCE vs. TEMPERATURE
40 OUTPUT RESISTANCE () 35 30 25 20 15 10 5 0 VIN = +5V VIN = +3.3V VIN = +2V VIN = +1.5V
MAX1697 TOC15
30 VIN = +1.5V 25 OUTPUT RESISTANCE () 20 15 10 5 0 -40 -20 0 20 40 60 VIN = +2V VIN = +3.3V VIN = +5V
35 30 OUTPUT RESISTANCE () 25 VIN = +2V 20 15 10 5 0 VIN = +3.3V VIN = +5V VIN = +1.5V
45
80
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
PUMP FREQUENCY vs. TEMPERATURE
MAX1697 TOC16
MAX1697R/S OUTPUT NOISE AND RIPPLE
MAX1697 TOC17
MAX1697T/U OUTPUT NOISE AND RIPPLE
MAX1697 TOC18
1000 MAX1697U PUMP FREQUENCY (kHz) 100 MAX1697T MAX1697S MAX1697R
VOUT MAX1697R (12kHz)
VOUT MAX1697T (125kHz)
10
VOUT MAX1697S (35kHz) VIN = +1.5V TO +5V
VOUT MAX1697U (250kHz)
1 -40 -20 0 20 40 60 80 TEMPERATURE (C) 20s/div VIN = +3.3V, IOUT = 5mA, 10mV/div, AC-COUPLED 2s/div VIN = +3.3V, IOUT = 5mA, 10mV/div, AC-COUPLED
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5
60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25C, unless otherwise noted.)
MAX1697R OUTPUT CURRENT vs. CAPACITANCE
0V MAX1697U (250kHz) VOUT, 2V/div 0V MAX1697T (125kHz) VOUT, 2V/div VIN = +4.75V, VOUT = -4.0V 60 OUTPUT CURRENT (mA) 50 40 30 20 10 0 400s/div 50s/div 0 5 10 15 20 25 30 35 40 45 50 CAPACITANCE (F) VIN = +1.9V, VOUT = -1.5V VIN = +3.15V, VOUT = -2.5V
MAX1697 TOC21
START-UP FROM SHUTDOWN
MAX1697 TOC19
START-UP FROM SHUTDOWN
MAX1697 TOC20
70
0V MAX1697S (35kHz) VOUT, 2V/div 0V MAX1697R (12kHz) VOUT, 2V/div SHDN
SHDN
MAX1697S OUTPUT CURRENT vs. CAPACITANCE
MAX1697 TOC22
MAX1697T OUTPUT CURRENT vs. CAPACITANCE
MAX1697 TOC23
MAX1697U OUTPUT CURRENT vs. CAPACITANCE
70 OUTPUT CURRENT (mA) 60 50 40 30 20 10 0 VIN = +1.9V, VOUT = -1.5V VIN = +3.15V, VOUT = -2.5V VIN = +4.75V, VOUT = -4.0V
MAX1697 TOC24
80 VIN = +4.75V, VOUT = -4.0V 70 OUTPUT CURRENT (mA) 60 50 40 30 20 10 0 0 5 10 15 20 25 30 35 40 VIN = +1.9V, VOUT = -1.5V VIN = +3.15V, VOUT = -2.5V
70 VIN = +4.75V, VOUT = -4.0V 60 OUTPUT CURRENT (mA) 50 40 30 VIN = +1.9V, VOUT = -1.5V 20 10 0 VIN = +3.15V, VOUT = -2.5V
80
45
0
1
2
3
4
5
6
7
8
9
10
0
1
2
3
4
5
6
7
8
9
10
CAPACITANCE (F)
CAPACITANCE (F)
CAPACITANCE (F)
MAX1697R OUTPUT RIPPLE vs. CAPACITANCE
MAX1697 TOC25
MAX1697S OUTPUT RIPPLE vs. CAPACITANCE
450 400 OUTPUT RIPPLE (mV) 350 300 250 200 150 100 50 0 VIN = +4.75V, VOUT = -4.0V VIN = +3.15V, VOUT = -2.5V VIN = +1.9V, VOUT = -1.5V
MAX1697 TOC26
500 450 400 OUTPUT RIPPLE (mV) 350 300 250 200 150 100 50 0 0 5 VIN = +4.75V, VOUT = -4.0V VIN = +3.15V, VOUT = -2.5V VIN = +1.9V, VOUT = -1.5V
500
10 15 20 25 30 35 40 45 50 CAPACITANCE (F)
0
5
10 15 20 25 30 35 40 45 50 CAPACITANCE (F)
6
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60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25C, unless otherwise noted.)
MAX1697T OUTPUT RIPPLE vs. CAPACITANCE
MAX1697 TOC27
MAX1697U OUTPUT RIPPLE vs. CAPACITANCE
450 400 OUTPUT RIPPLE (mV) 350 300 250 200 150 100 50 0 VIN = +4.75V, VOUT = -4.0V VIN = +3.15V, VOUT = -2.5V VIN = +1.9V, VOUT = -1.5V
MAX1697 TOC28
500 450 400 OUTPUT RIPPLE (mV) 350 300 250 200 150 100 50 0 0 1 2 3 4 5 6 7 8 9 VIN = +4.75V, VOUT = -4.0V VIN = +3.15V, VOUT = -2.5V VIN = +1.9V, VOUT = -1.5V
500
10
0
1
2
3
4
5
6
7
8
9
10
CAPACITANCE (F)
CAPACITANCE (F)
Pin Description
PIN NAME OUT IN C1GND FUNCTION Inverting Charge-Pump Output Power-Supply Voltage Input. Input range is 1.5V to 5.5V. Negative Terminal of the Flying Capacitor Ground Shutdown Input. Drive this pin high for normal operation; drive it low for shutdown mode. OUT is actively pulled to ground during shutdown. Positive Terminal of the Flying Capacitor
TE: ( INPUT 1.5V to 5.5V C3 2 6 C1+ IN C1 3 C1OUT
1
2 3 4
1 RL
NEGATIVE OUTPUT -1 VIN C2
MAX1697
ON OFF 5 SHDN GND 4
5
SHDN
Figure 1. Typical Application Circuit
6
C1+
Detailed Description
The MAX1697 capacitive 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.
Efficiency Considerations
The efficiency of the MAX1697 is dominated by its quiescent supply current (IQ) at low output current and by its output impedance (ROUT) at higher output current; it is given by: I OUT x ROUT 1 - VIN IOUT + IQ IOUT
_______________________________________________________________________________________
7
60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
S1 IN C1 S2 V+ REQUIV = 1 fOSC C1 C2 RL REQUIV VOUT
S3
S4
C2 VOUT = -(VIN)
Figure 3b. Equivalent Circuit
Thermal Shutdown
Figure 2. Ideal Voltage Inverter
fOSC V+ VOUT C2 RL
The MAX1697 has a thermal shutdown mode for additional protection against fault conditions. When the temperature of the die exceeds +150C, the internal clock stops, suspending the device's operation. The MAX1697 resumes operation when the die temperature falls 15C. This prevents the device from rapidly oscillating around the temperature trip point.
C1
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:
VRIPPLE = IOUT + 2 x IOUT x ESRC2 2(fOSC )C2
Figure 3a. Switched-Capacitor Model
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 resistances (typically 4 to 5 at VIN = +5V). The typical output impedance is more accurately determined from the Typical Operating Characteristics.
Current Limit
The MAX1697 limits its input current upon start-up to 170mA (typ). This prevents low-current or higher output impedance input supplies (such as alkaline cells) from being overloaded when power is applied or when the device awakes from shutdown.
Shutdown
The MAX1697 has a logic-controlled shutdown input. Driving SHDN low places the device in a low-power shutdown mode. The charge-pump switching halts, supply current is reduced to 2nA, and OUT is actively pulled to ground through a 3 resistance. 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.
8
Input Bypass Capacitor (C3) If necessary, bypass the incoming supply to reduce its AC impedance and the impact of the MAX1697's switching noise. A bypass capacitor with a value equal to that of C1 is recommended.
_______________________________________________________________________________________
60mA, SOT23 Inverting Charge Pump with Shutdown
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. is the number of parallel devices. Figure 5 shows the equation for calculating output resistance.
MAX1697
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 60mA.
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 dramatically. For applications requiring larger negative voltages, see the MAX865 and MAX868 data sheets. The maximum load current and startup current of the nth cascaded circuit must not exceed the maximum output current capability of the (n-1)th circuit to ensure proper startup.
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).
Paralleling Devices
Paralleling multiple MAX1697s 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
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.
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 MAX1697R MAX1697S MAX1697T MAX1697U FREQUENCY (kHz) 12 35 125 250 CAPACITOR (F) 22 6.8 2.2 1 TYPICAL ROUT () 12 12 12 12
Table 3. Capacitor Selection to Minimize Capacitor Size
PART MAX1697R MAX1697S MAX1697T MAX1697U FREQUENCY (kHz) 12 35 125 250 CAPACITOR (F) 10 3.3 1 0.47 TYPICAL ROUT () 17 17 17 17 9
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60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
...
2 3 C1 4 6 5 SHDN MAX1697 C1 1 +VIN 3 4 6 MAX1697 1 5 VOUT C2 D2 C3 C4 2 C1 SHDN 5 3 4 6 MAX1697 D1 1 C2 VOUT = (2VIN) (VFD1) - (VFD2) VOUT = -VIN 2 +VIN D1, D2 = 1N4148
...
C2
VOUT = -nVIN
Figure 4. Cascading MAX1697s to Increase Output Voltage
Figure 6. Combined Doubler and Inverter
+VIN 2 3 C1 4 6 5 SHDN ROUT OF SINGLE DEVICE ROUT = NUMBER OF DEVICES 1 MAX1697 C1
...
2 3 4 6 1 5 VOUT = -VIN C2 VOUT MAX1697 MAX1697 OUT 1 GND 4 V+ RL
...
Figure 7. Heavy Load Connected to a Positive Supply
Figure 5. Paralleling MAX1697s to Reduce Output Resistance
Chip Information
TRANSISTOR COUNT: 275
10
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60mA, SOT23 Inverting Charge Pump with Shutdown
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE 6 SOT23 PACKAGE CODE U6F-6 DOCUMENT NO. 21-0058
MAX1697
PACKAGE OUTLINE, SOT 6L BODY
21-0058
I
1
2
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6LSOT.EPS
11
60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE OUTLINE, SOT 6L BODY
21-0058
I
2
2
12
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60mA, SOT23 Inverting Charge Pump with Shutdown MAX1697
Revision History
REVISION NUMBER 3 REVISION DATE 12/08 DESCRIPTION Added additional available top mark for RoHS compliance PAGES CHANGED 1
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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600___________________ 13 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

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