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MAX679EUA+ |MAX679EUAMAXIMN/a270avaiRegulated 3.3V Charge Pump
MAX679EUA+TN/AN/a2500avaiRegulated 3.3V Charge Pump


MAX679EUA+T ,Regulated 3.3V Charge PumpFeaturesThe MAX679 step-up, regulated charge pump gener-♦ Regulated 3.3V ±4% Outputates a 3.3V ±4% ..
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MAX679EUA+-MAX679EUA+T
Regulated 3.3V Charge Pump
_______________General Description
The MAX679 step-up, regulated charge pump gener-
ates 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 DC-
DC 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% OutputUltra-Small:
1.1mm-High, 8-Pin μMAX Package
No Inductors RequiredUp to 1MHz Operation
(small external components)
Fits into 0.05 in.2Up to 85% Efficiency1.8V to 3.6V Input Voltage Range50μA Quiescent Supply Current1μA Shutdown Currentgulated 3.3V Charge Pump
C1-
PGNDGND
OUT
C1+SHDN
FSET
μMAX
TOP VIEW
MAX679
__________________Pin Configuration

MAX679
OUT
C1+
C1-OFF/ON
FSET
SHDN
INPUT
2V to 3.6VOUTPUT
3.3V, 20mA
CINCOUT
GNDPGND
__________Typical Operating Circuit

19-1217; Rev 0; 4/97
PART

MAX679C/D0°C to +70°C
TEMP. RANGEPIN-PACKAGE

Dice*
______________Ordering Information

*Dice are tested at TA= +25°C only.
MAX679EUA-40°C to +85°C8 μMAX
gulated 3.3V Charge PumpABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS

(VIN= VSHDN= VFSET= 2V, CIN= 4.7μF, C1 = 0.33μF, COUT= 10μF, TA= -40°C to +85°C,unless otherwise noted. Typical values
are at TA= +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 (VIN+ 0.3V)
C1+ to GND..............................................-0.3V to (VOUT+ 0.3V)
OUT Short to GND..............................................................10sec
Continuous Power Dissipation (TA= +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 VIN
VIN= 2V, IOUT= 10mA
VIN= 3.6V
VIN= 1.8V
VIN= 1.8V, VOUT> 3.17V
VIN= 2.5V, FSET = IN or GND
VOUT= 3.6V, SHDN= GND
OUT = GND, VIN= 3.3V
VIN= 3.3V
FSET = IN
CONDITIONS
80Efficiency100200Output Short-Circuit Current
kHz700100013000.81.61.83.6Input Voltage
Input Undervoltage Lockout Voltage
Switching Frequency0.11FSET, SHDNInput Leakage Current0.7 x0.5 x
VINVINFSET, SHDNInput Voltage High0.5 x0.3 x
VINVINFSET, SHDNInput Voltage Low20Output Current5080No-Load Supply Current1525Leakage Current into OUT in Shutdown15Supply Current in Shutdown
UNITSMINTYPMAXPARAMETER

2V < VIN< 3.3V,
0mA < IOUT< 20mA3.153.45
Output Voltage= 0°C to +85°C= -40°C to +85°C
3.173.33.43
gulated 3.3V Charge PumpEFFICIENCY
vs. OUTPUT CURRENT

X679 TO
C01a
OUTPUT CURRENT (mA)
(%
FSET = IN (1MHz)
VIN = 3.0VVIN = 3.5V
VIN = 2.4V
VIN = 2.0V
VIN = 1.8V
EFFICIENCY
vs. OUTPUT CURRENT
679 TO
C01b
OUTPUT CURRENT (mA)
(%
VIN = 3.5V
VIN = 3.0V
VIN = 2.4V
VIN = 2.0V
VIN = 1.8V
FSET = GND (330kHz)
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
AX679 TOC02a
OUTPUT CURRENT (mA)
(V
FSET = GND (330kHz)
DASHED LINES INDICATE
OUTPUT OUT OF REGULATION
VIN = 3.5VVIN = 3.0V
VIN = 2.4V
VIN = 2.0V
VIN = 1.8V
OUTPUT VOLTAGE
vs. OUTPUT CURRENT
679 TO
C02b
OUTPUT CURRENT (mA)
(V90
FSET = IN (1MHz)
DASHED LINES INDICATE
OUTPUT OUT OF REGULATION
VIN = 3.5V
VIN = 3.0V
VIN = 2.4V
VIN = 2.0VVIN = 1.8V
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
AX679 TOC
SUPPLY VOLTAGE (V)

SHDN = IN
SHDN = GND
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
AX679 TO
C06
TEMPERATURE (°C)
(n
VIN = 2.4V
__________________________________________Typical Operating Characteristics

(Typical Operating Circuit with: VIN= VSHDN= 2V, CIN= 4.7μF, C1 = 0.33μF, COUT= 10μF, tested in-circuit, TA= +25°C, unless
otherwise noted.)
PUMP FREQUENCY
vs. TEMPERATURE
679 TO
C08a
TEMPERATURE (°C)
(k
FSET = GND (330kHz)
VIN = 2.5V
PUMP FREQUENCY
vs. TEMPERATURE
AX679 TOC08b
TEMPERATURE (°C)
(kH
FSET = IN (1MHz)
VIN = 2.5V
OUTPUT RIPPLE (2mA LOAD)

AX679 TOC
VOUT
50mV/div
AC COUPLED
100μs/div
FSET = GND (330kHz)
gulated 3.3V Charge Pump____________________________Typical Operating Characteristics (continued)
(Typical Operating Circuit with: VIN= VSHDN= 2V, CIN= 4.7μF, C1 = 0.33μF, COUT= 10μF, tested in-circuit, TA= +25°C, unless
otherwise noted.)
______________________________________________________________Pin Description
NAMEFUNCTION
FSETSet Charge-Pump Frequency Input. FSET = GND selects 330kHz and FSET = IN selects 1MHz. Do not leave
FSET unconnected.SHDNShutdown Input. The device shuts down, the output disconnects from the input, and the supply current
decreases to 1μA when SHDNis a logic low. Connect SHDNto IN for normal operation.
PIN
INSupply Input. Connect to an input supply in the 1.8V to 3.6V range. Bypass IN to GND with a (COUT/ 2)μF
capacitor.GNDGround. Analog ground for internal reference and control circuitry.OUT3.3V Power Output. Bypass OUT to GND with an output filter capacitor (see the Design Proceduresection).C1+Positive Terminal of the Charge-Pump CapacitorC1-Negative Terminal of the Charge-Pump CapacitorPGNDPower Ground. Charge-pump current flows through this pin.
LOAD-TRANSIENT RESPONSE
(1mA TO 10mA LOAD, VIN = 3V)

MAX679 TOC11
VOUT
10mV/div
AC COUPLED
IOUT
5mA/div
100μs/div
VIN = 3V
FSET = IN (1MHz)
LOAD-TRANSIENT RESPONSE
(1mA TO 10mA LOAD, VIN = 2V)

MAX679 TOC12
VOUT
10mV/div
AC COUPLED
IOUT
5mA/div
50μs/div
VIN = 2V
FSET = IN (1MHz)
_______________Detailed Description

The MAX679 regulated charge pump has a 50% duty-
cycle clock. In phase one (charge phase), the charge-
transfer capacitor (C1) charges to the input voltage,
and output current is delivered by the output filter
capacitor (COUT). In phase two (transfer phase), C1 is
placed in series with the input and connects to the out-
put, transferring its charge to COUT. If the clock were to
run continuously, this process would eventually gener-
ate an output voltage equal to two times the input volt-
age (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 COUT.
Start-Up Sequence

The MAX679 soft-start circuitry prevents excessive cur-
rent 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
VOUT
50mV/div
AC COUPLED
100μs/div
FSET = IN (1MHz)
gulated 3.3V Charge PumpOUTΦSW
PGND
C1-
C1+
10% OF N1
ΦSC
PULSER
ΦSW
ΦSC
CLOCK
RESET
212 COUNTER
OSCILLATOR +
CONTROL LOGIC
CHIP SUPPLY
OUT
FSET
SHDN
1.25V REF
GND
EAOUT (1 = OUTPUT OVER REGULATION POINT)
MAX679
ΦSW
ΦT
ΦC
ΦSC
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.gulated 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.
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.ycles (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 SHDNinput.
__________________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
COUT.
For lowest output ripple, select 1MHz operation (FSET
= IN). In addition, increasing COUTrelative to C1 will
further reduce ripple. For highest efficiency, select
330kHz operation (FSET = GND) and select the largest
practical values for COUTand 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 capaci-
tors can provide such low ESR; therefore, the output fil-
ter 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, COUT, 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 = VOUT/ (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
(μF)
COUT
(μF)
0.3310
FSET
(Hz)
Vp-p
(mV)
VIN
(V)
7330k20.330.13.3
3.316330k20.10.331027330k30.330.13.3
3.372330k30.1
X7R(714) 960-6492(714) 969-2491
Surface-Mount
Ceramic CapacitorsMatsuo
Sprague593D, 595D series
X7R
(603) 224-1961(603) 224-1430
(803) 626-3123(803) 946-0690AVX
MANUFACTURERCAPACITORS

Surface-Mount
Tantalum Capacitors
AVXTPS series
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(803) 946-0690(803) 626-3123
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