_______________General Description
The MAX679 step-up, regulated charge pump generates a 3.3V ±4% output voltage from a 1.8V to 3.6V
input voltage (two alkaline, NiCd, or NiMH; or one
Lithium-Ion battery). Output current is 20mA (min) from
a 2.0V input. Only three external capacitors are needed
to build a complete DC-DC converter.
The MAX679’s switching frequency is pin selectable at
330kHz or 1MHz to allow trade-offs between lowest
supply current and smallest-size capacitors. The logic
shutdown function reduces the supply current to 5µA
(max) and disconnects the load from the input. Special
soft-start circuitry prevents excessive current from
being drawn from the battery during start-up. This DCDC converter requires no inductors and has low EMI. It
is available in the ultra-small µMAX package, which is
only 1.11mm high and half the area of an 8-pin SO.
________________________Applications
Battery-Powered Applications
Miniature Equipment
Backup-Battery Boost Converters
Translators
Two-Way Pagers
____________________________Features
♦ Regulated 3.3V ±4% Output
♦ Ultra-Small:
1.1mm-High, 8-Pin µMAX Package
♦ No Inductors Required
♦ Up to 1MHz Operation
(small external components)
♦ Fits into 0.05 in.
2
♦ Up to 85% Efficiency
♦ 1.8V to 3.6V Input Voltage Range
♦ 50µA Quiescent Supply Current
♦ 1µA Shutdown Current
MAX679
Regulated 3.3V Charge Pump
________________________________________________________________
Maxim Integrated Products
1
C1-
PGND
GND
1
2
87OUT
C1+
SHDN
IN
FSET
µMAX
TOP VIEW
3
4
6
5
MAX679
__________________Pin Configuration
MAX679
OUT
C1+
C1-
OFF/ON
IN
FSET
SHDN
INPUT
2V to 3.6V
OUTPUT
3.3V, 20mA
C
IN
C
OUT
C1
GND
PGND
__________Typical Operating Circuit
19-1217; Rev 0; 4/97
PART
MAX679C/D 0°C to +70°C
TEMP. RANGE PIN-PACKAGE
Dice*
______________Ordering Information
*
Dice are tested at TA= +25°C only.
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
MAX679EUA -40°C to +85°C 8 µMAX
MAX679
Regulated 3.3V Charge Pump
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= V
SHDN
= V
FSET
= 2V, CIN= 4.7µF, C1 = 0.33µF, C
OUT
= 10µF, TA= -40°C to +85°C, unless otherwise noted. Typical values
are at T
A
= +25°C.) (Note 1)
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.
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
IN, OUT, SHDN, FSET to GND....................................-0.3V to 6V
PGND to GND.....................................................................±0.3V
C1- to GND..................................................-0.3V to (V
IN
+ 0.3V)
C1+ to GND..............................................-0.3V to (V
OUT
+ 0.3V)
OUT Short to GND..............................................................10sec
Continuous Power Dissipation (T
A
= +70°C)
µMAX (derate 4.1mW/°C above +70°C) .......................330mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +160°C
Lead Temperature (soldering, 10sec).............................+300°C
FSET = GND
FSET,SHDN = GND or V
IN
VIN= 2V, I
OUT
= 10mA
VIN= 3.6V
VIN= 1.8V
VIN= 1.8V, V
OUT
> 3.17V
VIN= 2.5V, FSET = IN or GND
V
OUT
= 3.6V, SHDN = GND
OUT = GND, VIN= 3.3V
VIN= 3.3V
FSET = IN
CONDITIONS
%80Efficiency
mA100 200Output Short-Circuit Current
kHz
700 1000 1300
V0.8 1.6
V1.8 3.6Input Voltage
Input Undervoltage Lockout Voltage
260 330 450
Switching Frequency
µA0.1 1
FSET, SHDN Input Leakage Current
V
0.7 x 0.5 x
V
IN
V
IN
FSET, SHDN Input Voltage High
V
0.5 x 0.3 x
V
IN
V
IN
FSET, SHDN Input Voltage Low
mA20Output Current
µA50 80No-Load Supply Current
µA15 25Leakage Current into OUT in Shutdown
µA1 5Supply Current in Shutdown
UNITSMIN TYP MAXPARAMETER
2V < VIN< 3.3V,
0mA < I
OUT
< 20mA
3.15 3.45
Output Voltage
TA= 0°C to +85°C
TA= -40°C to +85°C
V
3.17 3.3 3.43
MAX679
Regulated 3.3V Charge Pump
_______________________________________________________________________________________
3
0
EFFICIENCY
vs. OUTPUT CURRENT
20
10
MAX679 TOC01a
OUTPUT CURRENT (mA)
EFFICIENCY (%)
10
50
70
60
40
30
0.01 1
100
90
80
100
0.1
FSET = IN (1MHz)
VIN = 3.0V
VIN = 3.5V
VIN = 2.4V
VIN = 2.0V
V
IN
= 1.8V
0
0.01
EFFICIENCY
vs. OUTPUT CURRENT
20
10
30
MAX679 TOC01b
OUTPUT CURRENT (mA)
EFFICIENCY (%)
10
60
50
80
70
40
0.1 100
90
100
1
VIN = 3.5V
VIN = 3.0V
VIN = 2.4V
VIN = 2.0V
VIN = 1.8V
FSET = GND (330kHz)
2.8
0
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
3.0
2.9
MAX679 TOC02a
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
3.3
3.4
3.1
3.2
20 3010 60 70 80
3.5
3.6
40 50
FSET = GND (330kHz)
DASHED LINES INDICATE
OUTPUT OUT OF REGULATION
VIN = 3.5V
VIN = 3.0V
VIN = 2.4V
VIN = 2.0V
VIN = 1.8V
2.9
0
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
3.0
MAX679 TOC02b
OUTPUT CURRENT (mA)
OUTPUT VOLTAGE (V)
80 90
3.2
3.1
20 3010 60 70 100
3.3
3.4
40 50
FSET = IN (1MHz)
DASHED LINES INDICATE
OUTPUT OUT OF REGULATION
VIN = 3.5V
VIN = 3.0V
VIN = 2.4V
VIN = 2.0VVIN = 1.8V
0.1
1.8
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX679 TOC05
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (µA)
3.2 3.4
10
1
2.22.0 3.0 3.6
100
2.6 2.82.4
SHDN = IN
SHDN = GND
0
-40
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
100
MAX679 TOC06
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (nA)
60
300
400
200
-15 35 85
500
600
10
VIN = 2.4V
__________________________________________Typical Operating Characteristics
(Typical Operating Circuit with: VIN= V
SHDN
= 2V, CIN= 4.7µF, C1 = 0.33µF, C
OUT
= 10µF, tested in-circuit, TA= +25°C, unless
otherwise noted.)
300
-40
PUMP FREQUENCY
vs. TEMPERATURE
310
MAX679 TOC08a
TEMPERATURE (°C)
PUMP FREQUENCY (kHz)
60
330
340
320
-15 35 85
350
360
10
FSET = GND (330kHz)
V
IN
= 2.5V
900
-40
PUMP FREQUENCY
vs. TEMPERATURE
940
920
960
MAX679 TOC08b
TEMPERATURE (°C)
PUMP FREQUENCY (kHz)
60
1020
1000
1060
1040
980
-15 35 85
1080
1100
10
FSET = IN (1MHz)
V
IN
= 2.5V
OUTPUT RIPPLE (2mA LOAD)
MAX679 TOC09
V
OUT
50mV/div
AC COUPLED
100µs/div
FSET = GND (330kHz)
MAX679
Regulated 3.3V Charge Pump
4 _______________________________________________________________________________________
____________________________Typical Operating Characteristics (continued)
(Typical Operating Circuit with: VIN= V
SHDN
= 2V, CIN= 4.7µF, C1 = 0.33µF, C
OUT
= 10µF, tested in-circuit, TA= +25°C, unless
otherwise noted.)
______________________________________________________________Pin Description
NAME FUNCTION
1 FSET
Set Charge-Pump Frequency Input. FSET = GND selects 330kHz and FSET = IN selects 1MHz. Do not leave
FSET unconnected.
2
SHDN
Shutdown Input. The device shuts down, the output disconnects from the input, and the supply current
decreases to 1µA when SHDN is a logic low. Connect SHDN to IN for normal operation.
PIN
3 IN
Supply Input. Connect to an input supply in the 1.8V to 3.6V range. Bypass IN to GND with a (C
OUT
/ 2)µF
capacitor.
4 GND Ground. Analog ground for internal reference and control circuitry.
8 OUT 3.3V Power Output. Bypass OUT to GND with an output filter capacitor (see the
Design Procedure
section).
7 C1+ Positive Terminal of the Charge-Pump Capacitor
6 C1- Negative Terminal of the Charge-Pump Capacitor
5 PGND Power Ground. Charge-pump current flows through this pin.
_______________Detailed Description
The MAX679 regulated charge pump has a 50% dutycycle clock. In phase one (charge phase), the chargetransfer capacitor (C1) charges to the input voltage,
and output current is delivered by the output filter
capacitor (C
OUT
). In phase two (transfer phase), C1 is
placed in series with the input and connects to the output, transferring its charge to C
OUT
. If the clock were to
run continuously, this process would eventually generate an output voltage equal to two times the input voltage (hence the name “doubler”).
The charge pump regulates by gating the oscillator on
and off as needed to maintain output regulation. This
method has low quiescent current, but to achieve
acceptable output ripple, C1 must be significantly
lower in value than C
OUT
.
Start-Up Sequence
The MAX679 soft-start circuitry prevents excessive current from being drawn from the battery at start-up or
when the output is shorted. This is done by limiting the
charge pump to 1/10 the normal current until either the
output is in regulation or the first 4096 charge-pump
OUTPUT RIPPLE (2mA LOAD)
MAX679 TOC10
V
OUT
50mV/div
AC COUPLED
100µs/div
FSET = IN (1MHz)
LOAD-TRANSIENT RESPONSE
(1mA TO 10mA LOAD, V
IN
= 3V)
MAX679 TOC11
LOAD-TRANSIENT RESPONSE
(1mA TO 10mA LOAD, V
IN
= 2V)
MAX679 TOC12
VIN = 3V
FSET = IN (1MHz)
100µs/div
V
OUT
10mV/div
AC COUPLED
I
OUT
5mA/div
VIN = 2V
FSET = IN (1MHz)
50µs/div
V
OUT
10mV/div
AC COUPLED
I
OUT
5mA/div
MAX679
Regulated 3.3V Charge Pump
_______________________________________________________________________________________ 5
P6
IN OUT
P5
P4
Φ
SW
P3
Φ
T
Φ
C
P2
PGND
C1-
C1
C1+
10% OF N1
Φ
SC
Φ
C
N1
Φ
T
P1
PULSER
Φ
SW
Φ
C
Φ
T
Φ
SC
CLOCK
RESET
2
12
COUNTER
OSCILLATOR +
CONTROL LOGIC
CHIP SUPPLY
OUT
FSET
SHDN
1.25V REF
GND
EAOUT (1 = OUTPUT OVER REGULATION POINT)
MAX679
Φ
SW
Φ
T
Φ
C
Φ
SC
SWITCH CONNECTS OUT TO IN DURING START-UP
TRANSFER PHASE OF PUMP
CHARGE PHASE OF PUMP (FULL STRENGTH)
CHARGE PHASE OF PUMP (REDUCED STRENGTH)
=
=
=
=
Figure 1. Block Diagram
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.
6
___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
MAX679
Regulated 3.3V Charge Pump
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.
6
___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
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.
6
___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1997 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
cycles (about 4ms) have elapsed. The start-up
sequence begins at power-up, when exiting shutdown,
or when recovering from a short circuit. If VINis less
than the 1.6V UVLO threshold, the device remains shut
down and ignores a high SHDN input.
__________________Design Procedure
Optimize the charge-pump circuit for size, quiescent
current, and output ripple by properly selecting the
operating frequency and capacitors CIN, C1, and
C
OUT
.
For lowest output ripple, select 1MHz operation (FSET
= IN). In addition, increasing C
OUT
relative to C1 will
further reduce ripple. For highest efficiency, select
330kHz operation (FSET = GND) and select the largest
practical values for C
OUT
and C1 while maintaining a
30-to-1 ratio. See Table 1 for some suggested values
and the resulting output ripple.
Note that the capacitors must have low ESR (<20mΩ)
to maintain low ripple. Currently, only ceramic capacitors can provide such low ESR; therefore, the output filter capacitors should be a combination of a 1µF
ceramic capacitor and a 10µF tantalum capacitor.
Smallest Size
Set the frequency to 1MHz by connecting FSET to IN.
Table 1 shows typical external component values.
Table 1. External Component Selection
PC Board Layout
Place C1, C
OUT
, and CINclose to the IC. Connect
PGND and GND with a short trace.
Efficiency
Charge-pump efficiency is best at low frequency
(330kHz). The theoretical maximum efficiency is given
in the following equation:
Theoretical maximum efficiency = V
OUT
/ (2 x VIN)
Gate-charge losses amount to approximately 1mA from
the output at full switching frequency (about 5% to 7%
loss).
Table 2. Manufacturers of Low-ESR Capacitors
TRANSISTOR COUNT: 819
SUBSTRATE CONNECTED TO GND
___________________Chip Information
C1
(µF)
C
OUT
(µF)
2 0.33 10
10
FSET
(Hz)
Vp-p
(mV)
V
IN
(V)
1M 7
14330k2 0.33
2 0.1 3.3
3.3
1M 16
22330k2 0.1
3 0.33 10
10
1M 27
56330k3 0.33
3 0.1 3.3
3.3
1M 72
89330k3 0.1
X7R (714) 960-6492(714) 969-2491
Surface-Mount
Ceramic Capacitors
Matsuo
Sprague 593D, 595D series
X7R
(603) 224-1961 (603) 224-1430
(803) 626-3123(803) 946-0690AVX
MANUFACTURER CAPACITORS
Surface-Mount
Tantalum Capacitors
AVX TPS series
267 series
PHONE FAX
PRODUCTION
METHOD
(803) 946-0690 (803) 626-3123
(714) 960-6492(714) 969-2491Matsuo
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