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MAX1759EUB+-MAX1759EUB+T
Buck/Boost Regulating Charge Pump in µMAX
General DescriptionThe MAX1759 is a buck/boost regulating charge pump
that generates a regulated output voltage from a single
lithium-ion (Li+) cell, or two or three NiMH or alkaline
cells for small hand-held portable equipment. The
MAX1759 operates over a wide +1.6V to +5.5V input
voltage range and generates a fixed 3.3V or adjustable
(2.5V to 5.5V) output (Dual Mode™). Maxim’s unique
charge-pump architecture allows the input voltage to be
higher or lower than the regulated output voltage.
Despite its high 1.5MHz operating frequency, the
MAX1759 maintains low 50µA quiescent supply current.
Designed to be an extremely compact buck/boost con-
verter, this device requires only three small ceramic
capacitors to build a complete DC-DC converter capa-
ble of generating a guaranteed 100mA (min) output
current from a +2.5V input. For added flexibility, the
MAX1759 also includes an open-drain power-OK
(POK) output that signals when the output voltage is in
regulation.
The MAX1759 is available in a space-saving 10-pin
µMAX package that is 1.09mm high and half the size of
an 8-pin SO.
ApplicationsLi+ Battery-Powered Applications
Miniature Equipment
Backup Battery Boost Converters
Translators
FeaturesRegulated Output Voltage (Fixed 3.3V or
Adjustable 2.5V to 5.5V)100mA Guaranteed Output Current +1.6V to +5.5V Input Voltage RangeLow 50µA Quiescent Supply Current1µA Shutdown ModeLoad Disconnected from Input in ShutdownHigh 1.5MHz Operating FrequencyUses Small Ceramic CapacitorsShort-Circuit Protection and Thermal ShutdownSmall 10-Pin µMAX Package
MAX1759
Buck/Boost Regulating
Charge Pump in µMAXOUT
CXP
CXNIN
SHDN
POK
MAX1759
μMAX
TOP VIEW
PGNDGND
+1.6V TO +5.5V
OUT
3.3V AT 100mA
CIN
OFF
COUT
POWER OK
OUT
POK
CXNCXP
PGNDGNDFB
SHDN
MAX1759
Typical Operating Circuit19-1600; Rev 1; 6/00
PARTMAX1759EUB-40°C to +85°C
TEMP. RANGEPIN-PACKAGE10 µMAX
Pin Configuration
Ordering InformationDual Mode is a trademark of Maxim Integrated Products.
MAX1759
Buck/Boost Regulating
Charge Pump in µMAX
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VIN= VSHDN= 2V, FB = PGND = GND, CIN= 10µF, CX= 0.33µF, COUT= 10µF, TA
= 0°C to +85°C, unless oth-erwise 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, OUT, FB, POK, SHDNto GND............................-0.3V to +6V
PGND to GND.....................................................................±0.3V
CXN to GND................................................-0.3V to (VIN+ 0.3V)
CXP to GND................-0.3V to (the greater of VINor VOUT) + 1V
OUT Short to GND.........................................................Indefinite
Continuous Power Dissipation (TA= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C).........444mW
Operating Temperature Range..........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s)................................+300°C
ILOAD,MAX
Thermal Shutdown Hysteresis20°C
Efficiency90%VIN= 3.6V, ILOAD= 10mA
PARAMETERSYMBOLMINTYPMAXUNITSTransient Load Current200mA
Maximum Output Current100mA
3.173.33.43Output VoltageVOUT3.173.33.43V
Quiescent Supply CurrentIQ5090180µA
Shutdown Supply CurrentIQ,SHDN15µA
Leakage Current into OUT in
Shutdown15µA
Input Undervoltage Lockout
Voltage
Input Voltage RangeVIN1.65.5V
VUVLO0.61.01.4V
Output Voltage Adjustment Range2.55.5V
SHDNLogic Input VoltageVIL0.25 · VINVVIH0.7 ·VIN
SHDNInput Leakage CurrentISHDN-11µA
FB Regulation Voltage VFB1.2051.2351.265V
FB Input Current25200nA
FB Dual-Mode Threshold10050mV
200100mV
POK Trip Voltage1.01.11.2V
POK Output Low VoltageVOL5100mV
POK Leakage Current0.010.2µA
Switching FrequencyfOSC1.21.51.8MHz
Output Short-Circuit Current110mA
Thermal Shutdown Temperature160°C
CONDITIONS1.6V ≤VIN≤5.5V
ILOAD≤100mA (RMS)
1.6V ≤VIN≤5.5V
2.5V ≤VIN≤5.5V
2.5V ≤VIN≤5.5V, 1mA ≤ILOAD≤100mA
2V ≤VIN≤5.5V, 1mA ≤ILOAD≤50mA
VIN= VSHDN= 4V, VFB= 0, stepping down
VIN= VSHDN= 2V, VFB= 0, stepping upSHDN= 5.5V
VIN= 1.65V, VOUT= 3.3V
1.6V ≤VIN≤5.5V, VSHDN= 0
VIN= 2V, VOUT= 3.3V, VSHDN= 0
VFB= 1.27V
Internal feedback
External feedback
Falling edge at FB
ISINK= 0.5mA, VIN= 2V
VPOK= 5.5V, VFB= 1.27V
1.6V ≤VIN≤5.5V
1.6V ≤VIN≤5.5V, VFB= 1V
VOUT= 0, 2.5V ≤VIN≤5.5V, foldback current limit
Rising temperature
MAX1759
Buck/Boost Regulating
Charge Pump in µMAX
ELECTRICAL CHARACTERISTICS(Circuit of Figure 1, VIN= VSHDN= 2V, FB = PGND = GND, CIN= 10µF, CX= 0.33µF, COUT= 10µF, TA
= -40°C to +85°C, unless oth-erwisenoted.) (Note 1)
Note 1:Specifications to -40°C are guaranteed by design and are not production tested.
PARAMETERSYMBOLMINMAXUNITSQuiescent Supply CurrentIQ90
Maximum Output CurrentILOAD,MAX100mA
Output Voltage Adjustment
Range2.55.5V
3.153.45V
180µA
Shutdown Supply CurrentIQ,SHDN6µA
Leakage Current into OUT in
Shutdown5µA
SHDNInput Logic VoltageVIL0.2 ·VINV
Input Undervoltage Lockout
Voltage
Input Voltage RangeVIN1.65.5V
VUVLO0.61.4V
Output VoltageVOUT3.153.45V
VIH0.7 ·VINV
SHDNInput Leakage CurrentISHDN-11µA
FB Regulation Voltage VFB1.2051.265V
FB Input Bias Current200nA
FB Dual Mode Threshold40mV
200mV
POK Trip Voltage1.01.2V
POK Output Low VoltageVOL100mV
POK Leakage Current0.2µA
Switching FrequencyfOSC1.11.9MHz
CONDITIONS1.6V ≤VIN≤5.5V
VIN= VSHDN= 4V, VFB= 0
VSHDN= 5.5V
2.5V ≤VIN≤5.5V
1.6V ≤VIN≤5.5V
2.5V ≤VIN≤5.5V, 0 ≤ILOAD≤100mA
VIN= VSHDN= 2.5V, VFB= 0
1.6V ≤VIN≤5.5V, VSHDN= 0
VIN= 1.65V, VOUT = 3.3V
VFB= 1.27V
VIN= 2V, VOUT= 3.3V, VSHDN= 0
1.6V ≤VIN≤5.5V
Internal feedback
External feedback
Falling edge at FB
ISINK= 0.5mA, VIN= 2V
VPOK= 5.5V
1.6V ≤VIN≤5.5V, VFB= 1V
2V ≤VIN≤5.5V, 0 ≤ILOAD≤50mA
MAX1759
Buck/Boost Regulating
Charge Pump in µMAX
Typical Operating Characteristics(Circuit of Figure 1, CIN= 10µF, CX= 0.33µF, COUT= 10µF, VOUT= 3.3V, VIN= 2.5V, TA= +25°C, unless otherwise noted.)
OUTPUT VOLTAGE RIPPLE
vs. INPUT VOLTAGE
MAX1759 toc01
INPUT VOLTAGE (V)
OUTPUT VOLTAGE RIPPLE (mV)
IOUT = 10mA
IOUT = 50mA
IOUT = 100mA
OUTPUT VOLTAGE vs. LOAD CURRENTMAX1759 toc02
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
EFFICIENCY vs. INPUT VOLTAGE
MAX1759 toc03
INPUT VOLTAGE (V)
EFFICIENCY (%)
IOUT = 10mA
IOUT = 50mA
IOUT = 100mA
QUIESCENT CURRENT
vs. INPUT VOLTAGE
MAX1759 toc04
INPUT VOLTAGE (V)
QUIESCENT CURRENT (
10,000
NO LOAD
STARTUP INPUT VOLTAGE
(VOUT < VIN)
MAX1759 toc05
INPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
RLOAD = 33Ω
5μs/div
TYPICAL SWITCHING WAVEFORMS
(VOUT < VIN)MAX1759 toc06
CH1: VOUT, 20mV/div, AC-COUPLED
CH2: VCXP, 5V/div
CH3: VIN, 50mV/div, AC-COUPLED
RLOAD = 33Ω
VIN = 4.2V
5μs/div
TYPICAL SWITCHING WAVEFORMS
(VOUT > VIN)MAX1759 toc07
CH1: VOUT, 20mV/div, AC-COUPLED
CH2: VCXP, 5V/div
RLOAD = 33Ω
VIN = 2.5V
100μs/div
LOAD-TRANSIENT RESPONSE
(VOUT < VIN)MAX1759 toc08
CH1: VOUT, 20mV/div, AC-COUPLED
CH2: IOUT, 100mA/div
LOAD STEP: 10mA TO 100mA
VIN = 4.2V
100μs/div
LOAD-TRANSIENT RESPONSE
(VOUT > VIN)MAX1759 toc09
CH1: VOUT, 20mV/div, AC-COUPLED
LOAD STEP: 10mA TO 100mA
VIN = 2.5V
MAX1759
Buck/Boost Regulating
Charge Pump in µMAX
Typical Operating Characteristics (continued)(Circuit of Figure 1, CIN= 10µF, CX= 0.33µF, COUT= 10µF, VOUT= 3.3V, VIN= 2.5V, TA= +25°C, unless otherwise noted.)
NAMEFUNCTIONPOK
Open-Drain Power-OK Output. POK is high impedance when output voltage is in regulation. POK sinks current
when VFBfalls below 1.1V. Connect a 10kΩto 1MΩpull-up resistor from POK to VOUTfor a logic signal.
Ground POK or leave unconnected if not used. POK is high impedance in shutdown.SHDNShutdown Input. Drive high for normal operation; drive low for shutdown mode. OUT is high impedance in
shutdown.
PIN3, 4INInput Supply. Connect both pins together and bypass to GND with a ceramic capacitor (see Capacitor
Selectionsection).GNDGround. Connect GND to PGND with a short trace.OUTPower Output. Bypass to GND with an output filter capacitor.CXPPositive Terminal of the Charge-Pump Transfer CapacitorCXNNegative Terminal of the Charge-Pump Transfer CapacitorPGNDPower Ground. Charge-pump current flows through this pin.FBDual-Mode Feedback. Connect FB to GND for 3.3V output. Connect to an external resistor divider to adjust
the output voltage from 2.5V to 5.5V.
Pin Description-4.2V
-2.5V
100μs/div
LINE-TRANSIENT RESPONSEMAX1759 toc10
CH1: VOUT, 20mV/div, AC-COUPLED
CH2: VIN, 1V/div, AC-COUPLED
RLOAD = 33Ω
500μs/div
TURN-ON/OFF RESPONSE
(VIN = 4.2V)MAX1759 toc11
CH1: VOUT,1V/div
CH2: IIN, 200mA/div
CH3: VPOK, 5V/div
CH4: VSHDN, 5V/div
RLOAD = 33Ω
VIN = 4.2V
500μs/div
TURN-ON/OFF RESPONSE
(VIN = 2.5V)MAX1759 toc12
CH1: VOUT,1V/div
CH2: IIN, 200mA/div
CH3: VPOK, 5V/div
CH4: VSHDN, 5V/div
RLOAD = 33Ω
VIN = 2.5V
MAX1759
Buck/Boost Regulating
Charge Pump in µMAX
Detailed Description The MAX1759’s unique charge-pump architecture
allows the input voltage to be higher or lower than the
regulated output voltage. Internal circuitry senses VIN
and VOUTand determines whether VINmust be
stepped up or stepped down to produce the regulated
output. When VINis lower than VOUT, the charge pump
operates as a regulated step-up voltage doubler. When
VINis higher than VOUT, the charge pump operates as
a step-down gated switch.
In voltage step-down mode (i.e., the input voltage is
greater than the output voltage) with a light load, the
controller connects CXN to PGND, and shuttles charge
to the output by alternately connecting CXP from IN to
OUT (see Figures 1 and 2). Although VINis greater than
VOUT, this scheme may not allow the MAX1759 to regu-
late the output under heavy loads. In this case, the
MAX1759 will automatically switch to step-up mode.In
step-upmode, the output is kept in regulation by modu-
lating the charge delivered by the transfer capacitor
(CX) to the load (see Figure 2). When lightly loaded, the
charge pump switches only as necessary to supply the
load, resulting in low quiescent current. Output voltage
ripple does not increase with light loads.
Shutdown ModeDriving SHDNlow places the MAX1759 in shutdown
mode. This disables the charge-pump switches, oscil-
lator, and control logic, reducing quiescent current to
1µA. The output is high impedance in shutdown and is
disconnected from the input. The POK output is high
impedance in shutdown.
Undervoltage Lockout The MAX1759 undervoltage lockout feature deactivates
the device when the input voltage falls below 1V.
Power-OK OutputPOK is an open-drain output that sinks current when
the regulator feedback voltage falls below 1.1V. The
feedback voltage can be either the internal resistor-
divider feedback voltage when in fixed output mode
(FB tied to GND) or an external feedback voltage from
an external resistive divider in adjustable output mode.
A 10kΩto 1MΩpull-up resistor from POK to OUT may
be used to provide a logic output. Connect POK to GND
or leave unconnectedif not used.
Soft-Start and Short-Circuit ProtectionThe MAX1759 features foldback short-circuit protec-
tion. This circuitry provides soft-start by limiting inrush
current during startup and limits the output current to
110mA (typ) if the output is short-circuited to ground.
Thermal ShutdownThe MAX1759 features thermal shutdown with tempera-
ture hysteresis. When the die temperature exceeds
160°C, the device shuts down. When the die cools by
20°C, the MAX1759 turns on again. If high die tempera-
ture is caused by output overload and the load is not
removed, the device will turn off and on, resulting in a
pulsed output.
Design Procedure
Setting the Output VoltageThe MAX1759 dual-mode feedback controller selects
between the internally set 3.3V regulated output or an
external resistive divider that allows adjustment of the
output voltage from 2.5V to 5.5V. Connect FB to GND
for a regulated 3.3V output. For an adjustable output,
connect a resistive divider between OUT and GND. To
ensure feedback-loop stability and to minimize error due
to FB pin bias currents, the resistivedivider current
should be approximately 15µA. In the following equa-
tion, choose R2 in the 50kΩto 100kΩrange, and calcu-
late R1 from the following formula (Figure 3):
R1 = R2 [(VOUT / VFB) - 1]
and
VOUT= VFB(R1 + R2) / R2
where VOUTis the desired output voltage from 2.5V to
5.5V, and VFBis the internal regulation voltage, nomi-
nally 1.235V.
The circuit of Figure 3 generates a regulated 2.5V, using
external standard 1% resistor values. Surface-mount
resistors should be placed close to the MAX1759, less
than 5mm away from FB (see the PC Board Layout
section).
0.33μF
+1.6V TO +5.5V
OUT
3.3V AT 100mA
10μF
OFF
10μF
100k
POWER OK
OUT
POK
CXNCXP
PGNDGNDFB
SHDN
MAX1759
Figure 1. Typical Application Circuit
