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19-1218; Rev 1; 6/97
EVALUAATVIOANILKAIBTLMEANUAL
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
_______________General Description
The MAX863 dual-output DC-DC converter contains
two independent step-up controllers in a single com-
pact package. This monolithic bi-CMOS design draws
only 85µA when both controllers are on. The input
range extends down to 1.5V, permitting use in organiz-
ers, translators, and other low-power hand-held prod-
ucts. The MAX863 provides 90% efficiency at output
loads from 20mA to over 1A. This space-saving device
is supplied in a 16-pin QSOP package that fits in the
same area as an 8-pin SOIC.
The device uses a current-limited, pulse-frequency-
modulated (PFM) control architecture that reduces start-
up surge currents and maintains low quiescent currents
for excellent low-current efficiency. Each controller
drives a low-cost, external, N-channel MOSFET switch,
whose size can be optimized for any output current or
voltage.
In larger systems, two MAX863s can be used to gener-
ate 5V, 3.3V, 12V, and 28V from just two or three bat-
tery cells. An evaluation kit (MAX863EVKIT) is available
to speed designs. For a single-output controller, refer to
the MAX608 and MAX1771 data sheets.
________________________Applications
2- and 3-Cell Portable Equipment
Organizers
Translators
Hand-Held Instruments
Palmtop Computers
Personal Digital Assistants (PDAs)
Dual Supply (Logic and LCD)
__________________Pin Configuration
TOP VIEW
SENSE1 1
VDD 2
FB1 3
BOOT 4
CS1 5
EXT1 6
GND 7
PGND 8
MAX863
QSOP
16 REF
15 SHDN2
14 LBI
13 LBO
12 FB2
11 SHDN1
10 CS2
9 EXT2
____________________________Features
o Smallest Dual Step-Up Converter: 16-Pin QSOP
o 90% Efficiency
o 1.5V Start-Up Voltage
o 85µA Max Total Quiescent Supply Current
o 1µA Shutdown Mode
o Independent Shutdown Inputs
o Drives Surface-Mount, Dual N-Channel MOSFETs
o Low-Battery Input/Output Comparator
o Step-Up/Down Configurable
______________Ordering Information
PART
MAX863C/D
MAX863EEE
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
*Dice are tested at TA = +25°C.
PIN-PACKAGE
Dice*
16 QSOP
__________Typical Operating Circuit
VIN
OUT1
SENSE1 VDD BOOT
N EXT1 EXT2
CS1 CS2
OUT2
N
MAX863
LOW-BATTERY
DETECTOR OUTPUT
LBO
LBI
FB2
SHDN1
SHDN2
REF
FB1 PGND GND
ON/OFF
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800

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Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
ABSOLUTE MAXIMUM RATINGS
VDD to GND ............................................................-0.3V to +12V
PGND to GND .......................................................-0.3V to +0.3V
SHDN1, SHDN2, SENSE1, LBO to GND ................-0.3V to +12V
EXT1, EXT2 to PGND..................................-0.3V to (VDD + 0.3V)
FB1, FB2, CS1, CS2, SEL,
LBI, BOOT to GND.................................-0.3V to (VDD + 0.3V)
LBO Continuous Output Current.........................................15mA
EXT1, EXT2 Continuous Output Current .............................50mA
Continuous Power Dissipation (TA = +70°C)
QSOP (derate 8.30mW/°C above +70°C) ...................667mW
Operating Temperature Range
MAX863EEE ....................................................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°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
(VDD = +5V, ILOAD = 0mA, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.)
PARAMETER
VDD Input Voltage
OUT1 Output Voltage
(Note 3)
Quiescent Current
Shutdown Current
Load Regulation
Line Regulation
FB1, FB2, LBI
Threshold Voltage (Note 4)
FB1, FB2, LBI Input Current
SHDN1, SHDN2, SEL, BOOT
Input High Voltage
SHDN1, SHDN2, SEL, BOOT
Input Low Voltage
SHDN1, SHDN2, SEL, BOOT
Input Current
CS1, CS2 Threshold Voltage
CS1, CS2 Input Current
Maximum Switch On-Time
Minimum Switch Off-Time
EXT Rise/Fall Time (Note 5)
EXT On-Resistance
LBO Leakage Current
LBO Low Level
SYMBOL
VDD
VOUT1
IDD
IDD, SHDN
VFB, VLBI
IFB, ILBI
VIH
VIL
II
VCS
tON
tOFF
ILBO
VLBO,L
CONDITIONS
VDD = OUT1 = BOOT (Note 1)
(Note 2)
FB1 = VDD
FB1 = GND
SHDN1 = SHDN2 = VDD, measured from VDD
SHDN1 = VDD, SHDN2 = GND,
measured from VDD
SHDN1 = SHDN2 = GND
VIN = 3.3V, VOUT1 = 5V,
ILOAD = 0mA to 500mA, Figure 2
VIN = 2.7V to 5V, VOUT1 = 5V,
ILOAD = 300mA, Figure 2
2.7V < VDD < 11V
VDD = 1.5V
2.7V < VDD < 11V
VDD = 1.5V
Logic input = VDD or GND
CLOAD = 1nF, 10% to 90%
VLBO = 11V, VLBI > 1.275V
ILBO,SINK = 1mA, VLBI < 1.225V
MIN TYP MAX UNITS
1.5 11
V
2.7 11
3.2 3.3 3.4
4.85 5 5.15
V
50 85
µA
35 60
1 µA
40 mV/A
8 mV/V
1.225 1.25 1.275
2 10
1.6
0.7 x VDD
0.4
0.2 x VDD
1
85 100 115
1 25
14 17.5 22
1.6 2 2.4
50
5
1
0.1 0.4
V
nA
V
V
µA
mV
µA
µs
µs
ns
µA
V
2 _______________________________________________________________________________________

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Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
ELECTRICAL CHARACTERISTICS
(VDD = +5V, ILOAD = 0mA, TA = 0°C to +85°C, unless otherwise noted.) (Note 6)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX
VDD Input Voltage
VDD
VDD = OUT1 (Note 1)
(Note 2)
1.6 11
2.8 11
OUT1 Output Voltage
(Note 3)
Quiescent Current
Shutdown Current
FB1, FB2 Threshold Voltage
CS1, CS2 Threshold Voltage
VOUT1
IDD
IDD, SHDN
VFB
VCS
FB1 = VDD
FB1 = GND
SHDN1 = SHDN2 = VDD, measured from VDD
SHDN1 = VDD, SHDN2 = GND,
measured from VDD
SHDN1 = SHDN2 = GND
3.15
4.8
1.21
85
3.45
5.2
85
60
1
1.285
115
Note 1: When bootstrapped, an internal low-voltage oscillator drives the EXT1 pin rail-to-rail for low supply voltages.
Note 2: For non-bootstrapped operation, VDD > 2.7V is required to allow valid operation of all internal circuitry.
Note 3: For adjustable output voltages, see the Set the Output Voltage section.
Note 4: Measured with LBI falling. Typical hysteresis is 15mV.
Note 5: EXT1 and EXT2 swing from VDD to GND.
Note 6: Specifications to -40°C are guaranteed by design and not production tested.
UNITS
V
V
µA
µA
V
mV
__________________________________________Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(VOUT1 = 3.3V, BOOTSTRAPPED)
100
90
80
70
60
B
A
C
50
40
30
20
10
0
0.01
VOUT1 = 3.3V
A: VIN = 1.5V
B: VIN = 2.4V
C: VIN = 2.7V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
EFFICIENCY vs. OUTPUT CURRENT
(VOUT1 = 5.0V, BOOTSTRAPPED)
100
F
90
80
70
60
50
40
30
20
10
0
0.01
DE
C
B
A
VOUT1 = 5.0V
A: VIN = 1.5V
B: VIN = 2.4V
C: VIN = 2.7V
D: VIN = 3.3V
E: VIN = 3.6V
F: VIN = 4.0V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
EFFICIENCY vs. OUTPUT CURRENT
(VOUT1 = 5.0V, NON-BOOTSTRAPPED)
100
D
90
80
C
70 B
A
60
50
40
30
20
10
0
0.01
VOUT1 = 5.0V
A: VIN = 2.7V
B: VIN = 3.3V
C: VIN = 3.6V
D: VIN = 4.0V
0.1 1 10 100 1000
OUTPUT CURRENT (mA)
_______________________________________________________________________________________ 3

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Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
____________________________Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(VOUT1 = 12V, NON-BOOTSTRAPPED)
100
90
80
70
60
50
40
30
20
10
0
0.01
D
C
B
E
A
VOUT1 = 5.0V
A: VIN = 2.7V
B: VIN = 3.3V
C: VIN = 3.6V
D: VIN = 4.0V
E: VIN = 6.0V
0.1 1 10 100
OUTPUT CURRENT (mA)
1000
VDD CURRENT
vs. VDD VOLTAGE
60
BOTH ON
50
40 CONVERTER 1 ON
30 CONVERTER 2 ON
20
10
BOOTSTRAPPED-MODE MINIMUM
START-UP INPUT VOLTAGE
vs. OUTPUT CURRENT
3.5
3.0
VOUT1 = 5V
2.5
2.0
1.5 VOUT1 = 3.3V
1.0
0.5
1
1
10 100
OUTPUT CURRENT (mA)
1000
EXT RISE AND FALL TIMES vs.
SUPPLY VOLTAGE AND MOSFET CAPACITANCE
140
120
C,2
100
B,1
80
C,1
A: 470pF
B: 1.0nF
C: 2.2nF
1: RISE
2: FALL
60 B,2
A,1
40
A,2
20
0
0 24 6 8
VDD VOLTAGE (V)
Cond: Single +5V
LOAD-TRANSIENT RESPONSE
10 12
0
0 2 4 6 8 10 12
RESPONSE ENTERING/
SUPPLY VOLTAGE (V)
Cond: Single 5V
EXITING SHUTDOWN (BOOTSTRAPPED)
LINE-TRANSIENT RESPONSE
A
AA
BB
C 3.3V
C
B
100µs/div
VOUT1 = 3.3V, IOUT1 = 100mA TO 600mA
A: VOUT1, 100mV/div, 3.3V DC OFFSET
B: IOUT1, 200mA/div
200µs/div
VOUT1 = 3.3V, IOUT1 = 100mA, VIN = 2.4V
A: SHDN1, 5V/div
B: INDUCTOR CURRENT, 2A/div
C: VOUT1, 3.3V OFFSET, 500mV/div
500µs/div
VOUT1 = 5V, IOUT1 = 800mA
A: VIN = 2.7V TO 3.7V, 500mV/div
B: VOUT1, AC COUPLED, 50mV/div
C: INDUCTOR CURRENT, 2A/div
4 _______________________________________________________________________________________
0A

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Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
______________________________________________________________Pin Description
PIN NAME
FUNCTION
1 SENSE1 Feedback Input for DC-DC Controller 1 in Fixed-Output Mode
2 VDD IC Power-Supply Input
Adjustable Feedback and Preset Output Voltage Selection Input for DC-DC Controller 1. Connect to VDD
3 FB1 for 3.3V preset output or to GND for 5V output. Connect a resistor voltage divider to adjust the output volt-
age. See the section Set the Output Voltage.
Bootstrap Low-Voltage-Oscillator Enable Input. BOOT is an active-high, logic-level input. It enables the
4
BOOT
low-voltage oscillator to allow start-up from input voltages down to 1.5V while in a bootstrapped circuit
configuration. Connect BOOT to GND when in a non-bootstrapped configuration. If BOOT is high, VDD
must be connected to OUT1.
5 CS1 Input to the Current-Sense Comparator of DC-DC Controller 1
6
EXT1
Gate-Drive Output of DC-DC Controller 1. Drives an external N-channel power MOSFET.
7
GND
Analog Ground for Internal Reference, Feedback, and Control Circuits
8 PGND High-Current Ground Return for Internal MOSFET Drivers
9
EXT2
Gate-Drive Output of DC-DC Controller 2. Drives an external N-channel power MOSFET.
10 CS2 Input to the Current-Sense Amplifier of DC-DC Controller 2
11 SHDN1 Active-Low Shutdown Input for DC-DC Controller 1. Connect to VDD for normal operation.
12
FB2
Adjustable Feedback Input for DC-DC Controller 2. Connect a resistor voltage divider to adjust the output
voltage. See the section Set the Output Voltage.
13
LBO
Low-Battery Output. An open-drain N-channel MOSFET output. Sinks current when the voltage on LBI
drops below 1.25V. If unused, connect to GND.
14
LBI
Low-Battery Comparator Input. When the voltage on LBI drops below 1.25V, LBO sinks current. If unused,
connect to GND.
15 SHDN2 Active-Low Shutdown Input for DC-DC Controller 2. Connect to VDD for normal operation.
16 REF Reference Bypass Input. Connect a 0.1µF ceramic capacitor from REF to GND.
_______________Detailed Description
The MAX863 dual, bi-CMOS, step-up, switch-mode
power-supply controller provides preset 3.3V, 5V, or
adjustable outputs. Its pulse-frequency-modulated
(PFM) control scheme combines the advantages of low
supply current at light loads and high efficiency with
heavy loads. These attributes make the MAX863 ideal
for use in portable battery-powered systems where
small size and low cost are extremely important, and
where low quiescent current and high efficiency are
needed to maximize operational battery life. Use of
external current-sense resistors and MOSFETs allows
the designer to tailor the output current and voltage
capability for a diverse range of applications.
PFM Control Scheme
Each DC-DC controller in the MAX863 uses a one-shot-
sequenced, current-limited PFM design, as shown in
Figure 1. Referring to the Typical Operating Circuit
(Figure 2) and the switching waveforms (Figures 3a–3f),
the circuit works as follows. Output voltage is sensed
by the error comparator using either an internal voltage
divider connected to SENSE1 or an external voltage
divider connected to FB1. When the output voltage
drops, the error comparator sets an internal flip-flop.
The flip-flop turns on an external MOSFET, which allows
inductor current to ramp-up, storing energy in a mag-
netic field.
_______________________________________________________________________________________ 5