MAXIM MAX1697

19-1499; Rev 0; 7/99
60mA, SOT23 Inverting Charge Pump
with Shutdown
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
12Ω 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.
Applications
Negative Supply from +5V or +3.3V Logic Supplies
Small LCD Panels
Features
♦ 60mA Output Current
♦ Low 12Ω Output Resistance
♦ 150µA Supply Current (MAX1697R)
♦ Requires Only Two 1µF Capacitors (MAX1697U)
♦ Start-Up Current Limited
♦ +1.25V to +5.5V Input Voltage Range
♦ 0.1µA Logic-Controlled Shutdown
♦ Slew-Rate Limited to Reduce EMI
♦ 6-Pin SOT23 Package
Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1697_EUT-T
-40°C to +85°C
6 SOT23-6
Note: 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.
GaAsFET Bias Supplies
PART NO.
SUFFIX
FREQUENCY
(kHz)
TOP
MARK
Handy-Terminals, PDAs
R
12
AABV
Battery-Operated Equipment
S
35
AABW
T
125
AABX
U
250
AABY
Pin Configuration
Typical Operating Circuit
1µF
TOP VIEW
INPUT
1.5V to 5.5V
C1+
C1OUT
IN
MAX1697U
SHDN
ON
OFF
NEGATIVE
OUTPUT
-1 · VIN
60mA
OUT
1
IN
2
C1-
3
MAX1697
6
C1+
5
SHDN
4
GND
1µF
GND
SOT23-6
________________________________________________________________ Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
MAX1697
General Description
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
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
Continuous Power Dissipation (TA = +70°C)
6-Pin SOT23 (derate 14mW/°C above +70°C) ................1.1W
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°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.
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.)
PARAMETER
CONDITIONS
MAX1697R/S, RL = 5kΩ
Supply Voltage Range
MAX1697T/U, RL = 5kΩ
Quiescent Supply Current
TA = 0°C to + 85°C
1.5
5.5
TA = +25°C
1.4
5.5
TA = 0°C to + 85°C
1.5
150
MAX1697S
350
650
MAX1697T
950
1700
MAX1697U
1800
3400
TA = +25°C
0.002
1
TA = +85°C
0.03
Output shorted to ground, TA = +25°C
Voltage Conversion Efficiency
IOUT = 0, TA = +25°C
7
12
17
MAX1697S
20
35
50
MAX1697T
70
125
180
MAX1697U
140
250
360
99
99.9
IOUT = 60mA
OUT to GND Shutdown
Resistance
SHDN = GND, OUT is internally pulled to GND
in shutdown
SHDN Input Logic Low
SHDN Bias Current
Wake-Up Time from Shutdown
12
TA = 0°C to +85°C
2.5V ≤ VIN ≤ 5.5V
8
2.0
VIN(MIN) ≤ VIN ≤ 2.5V
0.6
VIN(MIN) ≤ VIN ≤ 2.5V
0.2
IOUT = 15mA
TA = +25°C
-100
kHz
Ω
Ω
V
VIN - 0.2
2.5V ≤ VIN ≤ 5.5V
SHDN = GND or IN
µA
%
25
33
3
µA
mA
MAX1697R
Output Resistance (Note 1)
V
300
170
TA = +25°C
UNITS
5.5
MAX1697R
Short-Circuit Current
TA = +25°C
MAX
5.5
SHDN = GND
Oscillator Frequency
TYP
1.25
Shutdown Supply Current
SHDN Input Logic High
2
TA = +25°C
MIN
TA = +25°C
0.05
TA = +85°C
10
MAX1697R
1200
MAX1697S
600
MAX1697T
100
MAX1697U
70
_______________________________________________________________________________________
+100
V
nA
µs
60mA, SOT23 Inverting Charge Pump
with Shutdown
(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.)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
THERMAL SHUTDOWN
Trip Temperature
Temperature increasing
Hysteresis
150
°C
15
°C
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
MIN
MAX
MAX1697R/S
1.5
5.5
MAX1697T/U
1.6
5.5
Supply Voltage Range
RL = 5kΩ
Output Current
Continuous, long-term
60
MAX1697R
350
MAX1697S
750
MAX1697T
1800
Quiescent Current
MAX1697U
Oscillator Frequency
UNITS
V
mARMS
µA
3600
MAX1697R
6
21
MAX1697S
16
60
MAX1697T
60
200
MAX1697U
120
400
kHz
Output Resistance (Note 1)
IOUT = 60mA
33
Ω
OUT to GND Shutdown
Resistance
SHDN = GND, OUT is internally pulled to GND in
shutdown
8
Ω
SHDN Input Logic High
SHDN Input Logic Low
2.5V ≤ VIN ≤ 5.5V
VIN(MIN) ≤ VIN ≤ 2.5V
2.1
V
VIN - 0.2
2.5V ≤ VIN ≤ 5.5V
0.6
VIN(MIN) ≤ VIN ≤ 2.5V
0.2
V
Note 1: Output resistance is guaranteed with capacitor ESR of 0.3Ω or less.
Note 2: All specifications from -40°C to +85°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
3
MAX1697
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25°C, unless otherwise noted.)
-3.0
-3.5
VIN = +5V
VIN = +3.3V
-2.5
-3.0
-3.5
20
30
40
50
60
70
-3.5
10
20
30
40
50
60
70
0
80
10
20
30
40
50
60
70
OUTPUT CURRENT (mA)
MAX1697U
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697R
EFFICIENCY vs. OUTPUT CURRENT
MAX1697S
EFFICIENCY vs. OUTPUT CURRENT
-2.0
VIN = +3.3V
-2.5
-3.0
VIN = +5V
80
EFFICIENCY (%)
-1.5
90
-3.5
70
VIN = +3.3V
60
50
VIN = +2V
40
100
90
50
40
30
30
20
10
10
-5.0
0
20
30
40
50
60
70
VIN = +2V
0
0
80
VIN = +3.3V
60
20
VIN = +5V
80
70
-4.5
-4.0
VIN = +5V
80
EFFICIENCY (%)
-1.0
100
MAX1697 TOC04
VIN = +2V
10
20
30
40
50
60
70
0
80
10
20
30
40
50
60
70
80
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
MAX1697T
EFFICIENCY vs. OUTPUT CURRENT
MAX1697U
EFFICIENCY vs. OUTPUT CURRENT
MAX1697R/S/T/U
OUTPUT IMPEDANCE vs. INPUT VOLTAGE
80
VIN = +3.3V
50
90
VIN = +2V
40
VIN = +5V
80
EFFICIENCY (%)
70
60
100
70
VIN = +3.3V
60
50
VIN = +2V
40
30
30
20
20
10
10
10
20
30
40
50
60
OUTPUT CURRENT (mA)
70
80
25
20
15
10
5
0
0
0
30
MAX1697 TOC09
VIN = +5V
OUTPUT IMPEDANCE (Ω)
90
MAX1697 TOC07
100
0
VIN = +5V
OUTPUT CURRENT (mA)
-0.5
10
MAX1697 TOC03
-3.0
OUTPUT CURRENT (mA)
0
0
VIN = +3.3V
-2.5
-5.0
0
80
MAX1697 TOC05
10
-2.0
-4.5
-5.0
0
VIN = +2V
-1.5
-4.0
VIN = +5V
-4.5
-5.0
OUTPUT VOLTAGE (V)
-2.0
-4.0
-4.5
4
-1.5
MAX1697 TOC06
VIN = +3.3V
-1.0
OUTPUT VOLTAGE (V)
-2.0
VIN = +2V
-1.0
-0.5
MAX1697 TOC08
OUTPUT VOLTAGE (V)
-1.5
-4.0
-0.5
OUTPUT VOLTAGE (V)
VIN = +2V
0
MAX1697 TOC02
-0.5
-2.5
0
MAX1697 TOC01
0
-1.0
MAX1697T
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697S
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
MAX1697R
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
EFFICIENCY (%)
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
0
10
20
30
40
50
60
OUTPUT CURRENT (mA)
70
80
1.5
2.0
2.5
3.0
3.5
4.0
INPUT VOLTAGE (V)
_______________________________________________________________________________________
4.5
5.0
5.5
60mA, SOT23 Inverting Charge Pump
with Shutdown
MAX1697R/S/T/U
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1697 TOC11
VIN = +3.3V
VIN = +2V
10
2.5
3.0
3.5
4.0
4.5
5.0
5.5
15
VIN = +3.3V
10
VIN = +5V
-20
0
20
40
60
80
-40
-20
0
20
40
60
TEMPERATURE (°C)
TEMPERATURE (°C)
MAX1697S
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697T
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697U
OUTPUT RESISTANCE
vs. TEMPERATURE
VIN = +2V
20
15
VIN = +3.3V
10
VIN = +5V
25
VIN = +2V
20
10
5
0
0
20
40
60
80
VIN = +3.3V
15
5
0
VIN = +1.5V
30
VIN = +5V
-20
0
20
40
60
30
VIN = +2V
25
20
VIN = +3.3V
15
VIN = +5V
10
-40
80
MAX1697R/S
OUTPUT NOISE AND RIPPLE
0
20
40
60
80
MAX1697T/U
OUTPUT NOISE AND RIPPLE
MAX1697 TOC17
MAX1697 TOC16
-20
TEMPERATURE (°C)
PUMP FREQUENCY
vs. TEMPERATURE
MAX1697U
VIN = +1.5V
35
0
-40
TEMPERATURE (°C)
100
40
5
TEMPERATURE (°C)
1000
80
45
OUTPUT RESISTANCE (Ω)
25
35
OUTPUT RESISTANCE (Ω)
VIN = +1.5V
-20
VIN = +2V
20
INPUT VOLTAGE (V)
30
-40
25
0
-40
MAX1697 TOC13
2.0
VIN = +1.5V
5
0
1.5
OUTPUT RESISTANCE (Ω)
20
5
0
PUMP FREQUENCY (kHz)
VIN = +5V
15
30
MAX1697 TOC15
MAX1697S
MAX1697R
35
OUTPUT RESISTANCE (Ω)
MAX1697T
1.0
25
MAX1697 TOC14
SUPPLY CURRENT (mA)
1.5
0.5
30
SUPPLY CURRENT (nA)
MAX1697U
2.0
35
MAX1697 TOC10
2.5
MAX1697R
OUTPUT RESISTANCE
vs. TEMPERATURE
MAX1697 TOC12
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1697
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25°C, unless otherwise noted.)
MAX1697 TOC18
VOUT
MAX1697R
(12kHz)
VOUT
MAX1697T
(125kHz)
MAX1697T
MAX1697S
MAX1697R
10
VOUT
MAX1697S
(35kHz)
VOUT
MAX1697U
(250kHz)
VIN = +1.5V TO +5V
1
-40
-20
0
20
40
TEMPERATURE (°C)
60
80
20µs/div
VIN = 3.3V, IOUT = 5mA,
10mV/div, AC-COUPLED
2µs/div
VIN = 3.3V, IOUT = 5mA,
10mV/div, AC-COUPLED
_______________________________________________________________________________________
5
Typical Operating Characteristics (continued)
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25°C, unless otherwise noted.)
MAX1697R
OUTPUT CURRENT
vs. CAPACITANCE
START-UP FROM SHUTDOWN
MAX1697 TOC20
MAX1697 TOC19
0V
MAX1697U
(250kHz)
VOUT, 2V/div
0V
MAX1697S
(35kHz)
VOUT, 2V/div
0V
0V
MAX1697R
(12kHz)
VOUT, 2V/div
MAX1697T
(125kHz)
VOUT, 2V/div
SHDN
70
MAX1697 TOC21
START-UP FROM SHUTDOWN
VIN = +4.75V, VOUT = -4.0V
60
OUTPUT CURRENT (mA)
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
SHDN
VIN = +3.15V, VOUT = -2.5V
50
40
30
VIN = +1.9V, VOUT = -1.5V
20
10
0
50µs/div
400µs/div
0
5
10 15 20 25 30 35 40 45 50
CAPACITANCE (µF)
MAX1697T
OUTPUT CURRENT
vs. CAPACITANCE
50
40
VIN = +1.9V, VOUT = -1.5V
30
60
OUTPUT CURRENT (mA)
VIN = +3.15V, VOUT = -2.5V
VIN = +4.75V, VOUT = -4.0V
20
VIN = +3.15V, VOUT = -2.5V
50
40
30
VIN = +1.9V, VOUT = -1.5V
20
0
5
10
15
20
25
30
35
40
45
1
2
3
4
5
6
7
8
9
10
VIN = +1.9V, VOUT = -1.5V
20
0
1
2
4
5
500
350
VIN = +4.75V, VOUT = -4.0V
VIN = +3.15V, VOUT = -2.5V
VIN = +1.9V, VOUT = -1.5V
450
400
350
300
250
VIN = +4.75V, VOUT = -4.0V
200
VIN = +3.15V, VOUT = -2.5V
VIN = +1.9V, VOUT = -1.5V
150
100
100
50
50
0
MAX1697 TOC26
400
3
MAX1697S
OUTPUT RIPPLE vs. CAPACITANCE
OUTPUT RIPPLE (mV)
450
150
30
0
0
5
10 15 20 25 30 35 40 45 50
CAPACITANCE (µF)
6
7
CAPACITANCE (µF)
MAX1697 TOC25
500
200
40
CAPACITANCE (µF)
MAX1697R
OUTPUT RIPPLE vs. CAPACITANCE
250
VIN = +3.15V, VOUT = -2.5V
50
0
0
CAPACITANCE (µF)
300
60
10
0
0
VIN = +4.75V, VOUT = -4.0V
70
10
10
6
80
OUTPUT CURRENT (mA)
60
OUTPUT RIPPLE (mV)
OUTPUT CURRENT (mA)
70
70
MAX1697 TOC23
VIN = +4.75V, VOUT = -4.0V
MAX1697 TOC22
80
MAX1697U
OUTPUT CURRENT
vs. CAPACITANCE
MAX1697 TOC24
MAX1697S
OUTPUT CURRENT
vs. CAPACITANCE
0
5
10 15 20 25 30 35 40 45 50
CAPACITANCE (µF)
_______________________________________________________________________________________
8
9
10
60mA, SOT23 Inverting Charge Pump
with Shutdown
(Circuit of Figure 1, capacitors from Table 2, VIN = +5V, SHDN = IN, TA = +25°C, unless otherwise noted.)
MAX1697T
OUTPUT RIPPLE vs. CAPACITANCE
400
450
400
OUTPUT RIPPLE (mV)
350
300
250
VIN = +4.75V, VOUT = -4.0V
200
VIN = +3.15V, VOUT = -2.5V
150
VIN = +1.9V, VOUT = -1.5V
100
MAX1697 TOC28
450
OUTPUT RIPPLE (mV)
500
MAX1697 TOC27
500
MAX1697U
OUTPUT RIPPLE vs. CAPACITANCE
350
300
250
200
VIN = +4.75V, VOUT = -4.0V
150
VIN = +3.15V, VOUT = -2.5V
100
50
VIN = +1.9V, VOUT = -1.5V
50
0
0
0
1
2
3
4
5
6
7
8
9
10
0
1
2
CAPACITANCE (µF)
3
4
5
6
7
8
9
10
CAPACITANCE (µF)
Pin Description
PIN
NAME
1
OUT
2
3
4
C1
FUNCTION
Inverting Charge-Pump Output
IN
Power-Supply Voltage Input. Input
range is 1.5V to 5.5V.
C1-
Negative Terminal of the Flying
Capacitor
GND
Ground
5
SHDN
Shutdown Input. Drive this pin high
for normal operation; drive it low for
shutdown mode. OUT is actively
pulled to ground during shutdown.
6
C1+
Positive Terminal of the Flying
Capacitor
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
INPUT
1.5V to 5.5V
2
3
C1-
6
C1+
IN
OUT
C3
MAX1697
ON
OFF
5
SHDN
NEGATIVE
OUTPUT
-1 · VIN
1
RL
C2
GND
4
TE: (
Figure 1. Typical Application Circuit
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:
η≅
IOUT  IOUT ⋅ROUT 
1−

IOUT + IQ 
VIN

_______________________________________________________________________________________
7
MAX1697
Typical Operating Characteristics (continued)
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
S1
REQUIV
S2
IN
V+
C1
S3
VOUT
REQUIV =
1
fOSC · C1
C2
RL
C2
S4
VOUT = -(VIN)
Figure 3b. Equivalent Circuit
Thermal Shutdown
Figure 2. Ideal Voltage Inverter
fOSC
V+
VOUT
C1
C2
The MAX1697 has a thermal shutdown mode for additional protection against fault conditions. When the temperature 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 oscillating around the temperature trip point.
RL
Applications Information
Capacitor Selection
Figure 3a. Switched-Capacitor Model
where the output impedance is roughly approximated
by:
1
ROUT ≅
+ 2R
+ 4ESRC1 + ESRC2
f
( OSC ) ⋅C1 SW
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 4Ω to 5Ω 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 3Ω 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
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 ⋅IOUT ⋅ESRC2
2(fOSC )C2
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
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.
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
Layout and Grounding
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
is the number of parallel devices. Figure 5 shows the
equation for calculating output resistance.
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
MANUFACTURER
SERIES
PHONE
FAX
Surface-Mount
Tantalum
Surface-Mount
Ceramic
AVX
TPS series
803-946-0690
803-626-3123
Matsuo
267 series
714-969-2491
714-960-6492
Sprague
593D, 595D series
603-224-1961
603-224-1430
AVX
X7R
803-946-0690
803-626-3123
Matsuo
X7R
714-969-2491
714-960-6492
Table 2. Capacitor Selection to Minimize
Output Resistance
Table 3. Capacitor Selection to Minimize
Capacitor Size
PART
FREQUENCY
(kHz)
CAPACITOR
(µF)
TYPICAL
ROUT (Ω)
PART
FREQUENCY
(kHz)
CAPACITOR
(µF)
TYPICAL
ROUT (Ω)
MAX1697R
12
22
12
MAX1697R
12
10
17
MAX1697S
35
6.8
12
MAX1697S
35
3.3
17
MAX1697T
125
2.2
12
MAX1697T
125
1
17
MAX1697U
250
1
12
MAX1697U
250
0.47
17
_______________________________________________________________________________________
9
MAX1697
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.
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
SHDN
…
+VIN
2
3
C1
4
3
3
MAX1697
4
C1
6
1
C1
MAX1697
…
SHDN
VOUT
3
4
C1
1
6
5
SHDN
C4
VOUT = (2VIN) (VFD1) - (VFD2)
Figure 6. Combined Doubler and Inverter
GND
2
MAX1697
VOUT = -VIN
C2
…
2
C1
1
C3
Figure 4. Cascading MAX1697s to Increase Output Voltage
3
6
D2
VOUT = -nVIN
+VIN
MAX1697
C2
5
C2
4
D1, D2 = 1N4148
2
D1
1
6
5
+VIN
5
2
4
…
1
VOUT
5
VOUT = -VIN
V+
MAX1697
MAX1697
6
4
RL
OUT
1
Figure 7. Heavy Load Connected to a Positive Supply
C2
ROUT OF SINGLE DEVICE
ROUT = NUMBER OF DEVICES
Figure 5. Paralleling MAX1697s to Reduce Output Resistance
Chip Information
TRANSISTOR COUNT: 275
10
______________________________________________________________________________________
60mA, SOT23 Inverting Charge Pump
with Shutdown
6LSOT.EPS
______________________________________________________________________________________
11
MAX1697
________________________________________________________Package Information
MAX1697
60mA, SOT23 Inverting Charge Pump
with Shutdown
NOTES
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.
12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 1999 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.