General Description
The MAX1697 ultra-small, monolithic, CMOS charge-
pump voltage inverter accepts an input voltage ranging
from +1.25V to +5.5V. This device features an ultra-low
12Ωoutput 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.
Applications
Negative Supply from +5V or +3.3V Logic Supplies
Small LCD Panels
GaAsFET Bias Supplies
Handy-Terminals, PDAs
Battery-Operated Equipment
Features
♦♦60mA Output Current
♦♦Low 12ΩOutput Resistance
♦♦150µA Supply Current (MAX1697R)
♦♦Requires Only Two 1µF Capacitors (MAX1697U)
♦♦Start-Up Current Limited
♦♦+1.25V to +5.5V Input Voltage Range
♦♦Slew-Rate Limited to Reduce EMI
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
________________________________________________________________ Maxim Integrated Products 1
SHDN
5
TOP VIEW
IN
GND
C1-
C1+
OUT
SOT23
16
MAX1697
2
34
+
Pin Configuration
C1+ C1-
IN
SHDN
OUT
GND
ON
1μF
1μF
OFF
INPUT
1.5V to 5.5V
NEGATIVE
OUTPUT
-1 ✕ VIN
60mA
MAX1697U
Typical Operating Circuit
19-1499; Rev 3; 12/08
Note 1: The MAX1697 requires special solder temperature pro-
file 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.
Ordering Information
PART TEMP RANGE PIN-PACKAGE
MAX1697_EUT-T
-40°C to +85°C
6 SOT23
TOP MARK
PART NO.
SUFFIX
FREQUENCY
(kHz) -T +T #T
R 12 AABV AABV ACBT
S 35 AABW AABW ACCK
T 125 AABX AABX ACCL
U 250 AABY AABY ACCM
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.
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 ‘+’.
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.
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= 0°C to +85°C, unless otherwise noted. Typical values are at
TA= +25°C.)
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.
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
Continuous Power Dissipation (TA= +70°C)
6-Pin SOT23 (derate 14mW/°C above +70°C) (Note 5)...1.1W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature ..........................................................(Note 6)
MAX1697T/U, RL= 5kΩ
SHDN = GND or IN
VIN(MIN) ≤VIN ≤2.5V
MAX1697R/S, RL= 5kΩ
2.5V ≤VIN ≤5.5V
VIN(MIN) ≤VIN ≤2.5V
2.5V ≤VIN ≤5.5V
IOUT = 0, TA= +25°C
SHDN = GND, OUT is internally pulled to GND
in shutdown
TA= +25°C
TA= +25°C
SHDN = GND
IOUT = 60mA
CONDITIONS
10 nA
-100 0.05 +100
SHDN Bias Current
0.2 V
0.6
SHDN Input Logic Low
VIN - 0.2 V
2.0
SHDN Input Logic High
Ω38
OUT to GND Shutdown
Resistance
33 Ω
12 25
Output Resistance (Note 7)
1.4 5.5
1.5 5.5 V
1.25 5.5
Supply Voltage Range
%99 99.9Voltage Conversion Efficiency
20 35 50 kHzOscillator Frequency
0.03
1.5 5.5
µA
150 300
Quiescent Supply Current
(Note 9)
350 650
µA
0.002 1
Shutdown Supply Current
UNITSMIN TYP MAXPARAMETER
TA= 0°C to +85°C
TA= +25°C
TA= 0°C to +85°C
TA= +25°C
MAX1697S
MAX1697R
TA= +85°C
TA= +25°C
TA= 0°C to +85°C
TA= +25°C
TA= +85°C
TA= +25°C
MAX1697U
MAX1697T 950 1700
1800 3400
Output shorted to ground, TA= +25°C mA170Short-Circuit Current
71217
140 250 360
70 125 180
MAX1697R
MAX1697S
MAX1697T
MAX1697U
Note 5: Thermal properties are specified with product mounted on the PC board with one square-inch of copper area and still air.
Note 6: 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.
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= -40°C to +85°C, unless otherwise noted.) (Note 8)
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= 0°C to +85°C, unless otherwise noted. Typical values are at
TA= +25°C.)
CONDITIONS
150
UNITSMIN TYP MAXPARAMETER
Note 7: Output resistance is guaranteed with capacitor ESR of 0.3Ωor less.
Note 8: All specifications from -40°C to +85°C 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.
Trip Temperature °C
Hysteresis °C15
Temperature increasing
THERMAL SHUTDOWN
VRL= 5kΩSupply Voltage Range 1.6 5.5
MAX1697R
VIN(MIN) ≤VIN ≤2.5V
2.5V ≤VIN ≤5.5V
VIN(MIN) ≤VIN ≤2.5V
2.5V ≤VIN ≤5.5V
MAX1697T/U
1.5 5.5
µA
SHDN = GND, OUT is internally pulled to GND in
shutdown
350
Continuous, long-term
Quiescent Current
(Note 9)
750
MAX1697T
MAX1697R
IOUT = 60mA
CONDITIONS
1800
kHz
621
3600
MAX1697S
MAX1697U
Oscillator Frequency 16 60
MAX1697T 60 200
120 400
MAX1697S
MAX1697U
MAX1697R/S
0.2 V
0.6
SHDN Input Logic Low
VIN - 0.2 V
2.1
SHDN Input Logic High
Ω8
OUT to GND Shutdown
Resistance
33 ΩOutput Resistance (Note 7)
mARMS
60Output Current
UNITSMIN MAXPARAMETER
µsIOUT = 15mAWake-Up Time from Shutdown
70MAX1697U
600
100
1200MAX1697R
MAX1697S
MAX1697T
0
10
15
25
20
30
1.5 2.5 3.02.0 3.5 4.0 4.5 5.0 5.5
MAX1697R/S/T/U
OUTPUT IMPEDANCE vs. INPUT VOLTAGE
MAX1697 TOC09
INPUT VOLTAGE (V)
OUTPUT IMPEDANCE (Ω)
5
0
20
10
40
30
60
50
70
90
80
100
0203010 40 50 60 70 80
MAX1697U
EFFICIENCY vs. OUTPUT CURRENT
MAX1697 TOC08
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +2V
VIN = +5V
VIN = +3.3V
MAX1697
4 _______________________________________________________________________________________
0
20
10
40
30
60
50
70
90
80
100
0203010 40 50 60 70 80
MAX1697T
EFFICIENCY vs. OUTPUT CURRENT
MAX1697 TOC07
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +2V
VIN = +5V
VIN = +3.3V
-5.0
-4.0
-4.5
-3.0
-3.5
-2.0
-2.5
-1.5
-0.5
-1.0
0
0203010 40 50 60 70 80
MAX1697R
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697 TOC01
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
VIN = +2V
VIN = +5V
VIN = +3.3V
-5.0
-4.0
-4.5
-3.0
-3.5
-2.0
-2.5
-1.5
-0.5
-1.0
0
0203010 40 50 60 70 80
MAX1697U
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697 TOC04
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
VIN = +2V
VIN = +5V
VIN = +3.3V
-5.0
-4.0
-4.5
-3.0
-3.5
-2.0
-2.5
-1.5
-0.5
-1.0
0
0203010 40 50 60 70 80
MAX1697S
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697 TOC02
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
VIN = +2V
VIN = +5V
VIN = +3.3V
-5.0
-4.0
-4.5
-3.0
-3.5
-2.0
-2.5
-1.5
-0.5
-1.0
0
0203010 40 50 60 70 80
MAX1697T
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697 TOC03
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
VIN = +2V
VIN = +5V
VIN = +3.3V
0
20
10
40
30
60
50
70
90
80
100
0203010 40 50 60 70 80
MAX1697R
EFFICIENCY vs. OUTPUT CURRENT
MAX1697 TOC05
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +2V
VIN = +5V
VIN = +3.3V
0
20
10
40
30
60
50
70
90
80
100
0203010 40 50 60 70 80
MAX1697S
EFFICIENCY vs. OUTPUT CURRENT
MAX1697 TOC06
OUTPUT CURRENT (mA)
EFFICIENCY (%)
VIN = +2V
VIN = +5V
VIN = +3.3V
Typical Operating Characteristics
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= +25°C, unless otherwise noted.)
60mA, SOT23 Inverting Charge Pump
with Shutdown
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
_______________________________________________________________________________________ 5
0
0.5
1.0
2.0
1.5
2.5
1.5 2.5 3.02.0 3.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1697 TOC10
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
MAX1697R
MAX1697S
MAX1697T
MAX1697U
0
5
15
10
25
20
30
35
-40 0 20-20 406080
MAX1697R/S/T/U
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1697 TOC11
TEMPERATURE (°C)
SUPPLY CURRENT (nA)
VIN = +2V
VIN = +3.3V
VIN = +5V
0
5
15
10
25
20
30
35
-40 0 20-20 406080
MAX1697R
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697 TOC12
TEMPERATURE (°C)
OUTPUT RESISTANCE (Ω)
VIN = +2V
VIN = +1.5V
VIN = +5V
VIN = +3.3V
0
5
15
10
25
20
30
-40 0 20-20 406080
MAX1697S
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697 TOC13
TEMPERATURE (°C)
OUTPUT RESISTANCE (Ω)
VIN = +2V
VIN = +1.5V
VIN = +5V
VIN = +3.3V
1
100
10
1000
-40-200 20406080
PUMP FREQUENCY
vs. TEMPERATURE
MAX1697 TOC16
TEMPERATURE (°C)
PUMP FREQUENCY (kHz)
MAX1697U
MAX1697T
MAX1697S
MAX1697R
VIN = +1.5V TO +5V
0
5
15
10
25
20
30
35
-40 0 20-20 406080
MAX1697T
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697 TOC14
TEMPERATURE (°C)
OUTPUT RESISTANCE (Ω)
VIN = +2V
VIN = +1.5V
VIN = +5V
VIN = +3.3V
0
5
15
10
25
20
30
40
35
45
-40 0 20-20 40 60 80
MAX1697U
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697 TOC15
TEMPERATURE (°C)
OUTPUT RESISTANCE (Ω)
VIN = +2V
VIN = +1.5V
VIN = +5V
VIN = +3.3V
VOUT
MAX1697R
(12kHz)
VOUT
MAX1697S
(35kHz)
MAX1697R/S
OUTPUT NOISE AND RIPPLE
MAX1697 TOC17
20μs/div
VIN = +3.3V, IOUT = 5mA,
10mV/div, AC-COUPLED
VOUT
MAX1697T
(125kHz)
VOUT
MAX1697U
(250kHz)
MAX1697T/U
OUTPUT NOISE AND RIPPLE
MAX1697 TOC18
2μs/div
VIN = +3.3V, IOUT = 5mA,
10mV/div, AC-COUPLED
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= +25°C, unless otherwise noted.)
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= +25°C, unless otherwise noted.)
0V
SHDN
0V
MAX1697S
(35kHz)
VOUT, 2V/div
MAX1697R
(12kHz)
VOUT, 2V/div
START-UP FROM SHUTDOWN
MAX1697 TOC19
400μs/div
0V
0V
MAX1697U
(250kHz)
VOUT, 2V/div
MAX1697T
(125kHz)
VOUT, 2V/div
START-UP FROM SHUTDOWN
MAX1697 TOC20
50μs/div
SHDN
0
20
10
40
30
60
50
70
0 1015205 253035 4540 50
MAX1697R
OUTPUT CURRENT
vs. CAPACITANCE
MAX1697 TOC21
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
VIN = +4.75V, VOUT = -4.0V
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
0
20
10
40
30
60
50
70
80
0 1015205 2530354045
MAX1697S
OUTPUT CURRENT
vs. CAPACITANCE
MAX1697 TOC22
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
0
100
50
200
150
300
250
350
450
400
500
0 1015205 253035 4540 50
MAX1697R
OUTPUT RIPPLE vs. CAPACITANCE
MAX1697 TOC25
CAPACITANCE (μF)
OUTPUT RIPPLE (mV)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
0
20
10
40
30
60
50
70
0 2341 567 9810
MAX1697T
OUTPUT CURRENT
vs. CAPACITANCE
MAX1697 TOC23
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
VIN = +1.9V, VOUT = -1.5V
0
20
10
40
30
60
50
70
80
0 2341 567 9810
MAX1697U
OUTPUT CURRENT
vs. CAPACITANCE
MAX1697 TOC24
CAPACITANCE (μF)
OUTPUT CURRENT (mA)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
0
100
50
200
150
300
250
350
450
400
500
0 1015205 253035 4540 50
MAX1697S
OUTPUT RIPPLE vs. CAPACITANCE
MAX1697 TOC26
CAPACITANCE (μF)
OUTPUT RIPPLE (mV)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
Detailed Description
The MAX1697 capacitive charge pumps invert the volt-
age 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 half-
cycle, S1 and S3 open, S2 and S4 close, and C1 is level
shifted downward by VIN volts. This connects C1 in par-
allel 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 qui-
escent supply current (IQ) at low output current and by
its output impedance (ROUT) at higher output current; it
is given by:
I
II
1I x R
V
OUT
OUT Q
OUT OUT
IN
η≅ +−
⎛
⎝
⎜⎞
⎠
⎟
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
_______________________________________________________________________________________ 7
0
100
50
200
150
300
250
350
450
400
500
0 2341 567 9810
MAX1697T
OUTPUT RIPPLE vs. CAPACITANCE
MAX1697 TOC27
CAPACITANCE (μF)
OUTPUT RIPPLE (mV)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
0
100
50
200
150
300
250
350
450
400
500
0 2341 567 9810
MAX1697U
OUTPUT RIPPLE vs. CAPACITANCE
MAX1697 TOC28
CAPACITANCE (μF)
OUTPUT RIPPLE (mV)
VIN = +1.9V, VOUT = -1.5V
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
Pin Description
6Positive Terminal of the Flying
Capacitor
1Inverting Charge-Pump Output
2Power-Supply Voltage Input. Input
range is 1.5V to 5.5V.
3Negative Terminal of the Flying
Capacitor
4Ground
5
Shutdown Input. Drive this pin high
for normal operation; drive it low for
shutdown mode. OUT is actively
pulled to ground during shutdown.
PIN FUNCTIONNAME
C1+
OUT
IN
C1-
GND
SHDN
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA= +25°C, unless otherwise noted.)
TE: (
C1
C2
21
5
ON
OFF
3
RL
6
4
C3
C1+ C1-
IN
SHDN
OUT
GND
INPUT
1.5V to 5.5V NEGATIVE
OUTPUT
-1 ✕ VIN
MAX1697
Figure 1. Typical Application Circuit
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
8 _______________________________________________________________________________________
where the output impedance is roughly approximated
by:
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 4Ωto 5Ωat VIN = +5V). The typi-
cal 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 3Ωresistance.
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.
Thermal Shutdown
The MAX1697 has a thermal shutdown mode for addi-
tional protection against fault conditions. When the tem-
perature of the die exceeds +150°C, the internal clock
stops, suspending the device’s operation. The
MAX1697 resumes operation when the die temperature
falls 15°C. This prevents the device from rapidly oscil-
lating around the temperature trip point.
Applications Information
Capacitor Selection
The charge-pump output resistance is a function of the
ESR of C1 and C2. To maintain the lowest output resis-
tance, use capacitors with low ESR. (See Table 1 for a
list of recommended manufacturers.) Tables 2 and 3
suggest capacitor values for minimizing output resis-
tance or capacitor size.
Flying Capacitor (C1)
Increasing the flying capacitor’s value reduces the out-
put resistance. Above a certain point, increasing C1’s
capacitance has negligible effect because the output
resistance is then dominated by internal switch resis-
tance 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:
Input Bypass Capacitor (C3)
If necessary, bypass the incoming supply to reduce its
AC impedance and the impact of the MAX1697’s switch-
ing noise. A bypass capacitor with a value equal to that
of C1 is recommended.
V=
I
2(f )C2 2 I ESR
RIPPLE OUT
OSC OUT C2
+× ×
R1
f x C1
2R 4ESR ESR
OUT
OSC
SW C1 C2
≅
()
++ +
S1
IN
S2
S3 S4
C1
C2
VOUT = -(VIN)
Figure 2. Ideal Voltage Inverter
V+
C1
fOSC
C2 RL
VOUT
Figure 3a. Switched-Capacitor Model
REQUIV =
REQUIV
VOUT
RL
1
V+
fOSC ✕ C1 C2
Figure 3b. Equivalent Circuit
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
_______________________________________________________________________________________ 9
Surface-Mount
Tantalum
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METHOD
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803-626-3123
FAXMANUFACTURER
AVX
Matsuo
Sprague
SERIES
TPS series
267 series
593D, 595D series
714-969-2491
803-946-0690AVX
Matsuo 714-960-6492
803-626-3123X7R
X7R
Surface-Mount
Ceramic
Table 2. Capacitor Selection to Minimize
Output Resistance
Table 3. Capacitor Selection to Minimize
Capacitor Size
Table 1. Low-ESR Capacitor Manufacturers
Voltage Inverter
The most common application for these devices is a
charge-pump voltage inverter (Figure 1). This applica-
tion 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.
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 dra-
matically. 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.
Paralleling Devices
Paralleling multiple MAX1697s reduces the output resis-
tance. 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.
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.
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).
Layout and Grounding
Good layout is important, primarily for good noise per-
formance. To ensure good layout, mount all compo-
nents as close together as possible, keep traces short
to minimize parasitic inductance and capacitance, and
use a ground plane.
MAX1697R
MAX1697S
MAX1697T
MAX1697U
12
35
125
250
22
6.8
2.2
1
12
12
12
12
PART FREQUENCY
(kHz)
CAPACITOR
(µF)
TYPICAL
ROUT (Ω)
MAX1697R
MAX1697S
PART
MAX1697T
MAX1697U
FREQUENCY
(kHz)
CAPACITOR
(µF)
TYPICAL
ROUT (Ω)
12
35
125
250
10
3.3
1
0.47
17
17
17
17
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
10 ______________________________________________________________________________________
MAX1697
2
5
1
VOUT = (2VIN) -
(VFD1) - (VFD2)
C2
+VIN
C1
3
4
6VOUT = -VIN
C4
D1
D1, D2 = 1N4148
C3
D2
SHDN
Figure 6. Combined Doubler and Inverter
MAX1697
4
1
GND
OUT
V+
RL
Figure 7. Heavy Load Connected to a Positive Supply
TRANSISTOR COUNT: 275
MAX1697MAX1697
2
1VOUT
C2
2
+VIN
C1
C1
33
44
6
55
61
VOUT = -VIN
ROUT = ROUT OF SINGLE DEVICE
NUMBER OF DEVICES
…
…
SHDN
Figure 5. Paralleling MAX1697s to Reduce Output Resistance
Chip Information
MAX1697
MAX1697
2
1VOUT
C2
2
+VIN
C1
C2
SHDN
C1
33
44
6
55
61
VOUT = -nVIN
…
…
Figure 4. Cascading MAX1697s to Increase Output Voltage
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
______________________________________________________________________________________ 11
6LSOT.EPS
PACKAGE OUTLINE, SOT 6L BODY
21-0058
2
1
I
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
6 SOT23 U6F-6 21-0058
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
12 ______________________________________________________________________________________
PACKAGE OUTLINE, SOT 6L BODY
21-0058
2
2
I
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
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
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
60mA, SOT23 Inverting Charge Pump
with Shutdown
MAX1697
Revision History
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NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
3 12/08 Added additional available top mark for RoHS compliance 1
