19-1218; Rev 2; 2/98
L
MANUA
ION KIT
AT
EVALU
BLE
AVAILA
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
____________________________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
_______________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.
MAX863
______________Ordering Information
PART
MAX863C/D
MAX863EEE
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
PIN-PACKAGE
Dice*
16 QSOP
*Dice
are tested at T
A
= +25°C.
________________________Applications
2- and 3-Cell Portable Equipment
Organizers
Translators
Hand-Held Instruments
Palmtop Computers
Personal Digital Assistants (PDAs)
Dual Supply (Logic and LCD)
__________Typical Operating Circuit
V
IN
OUT1
SENSE1 V
DD
BOOT
N
EXT1
CS1
EXT2
CS2
N
OUT2
__________________Pin Configuration
TOP VIEW
SENSE1 1
V
DD
2
FB1 3
BOOT 4
CS1 5
EXT1 6
GND 7
PGND 8
16 REF
15 SHDN2
14 LBI
MAX863
LBO
LOW-BATTERY
DETECTOR OUTPUT
LBI
FB2
SHDN1
SHDN2
REF
FB1
PGND GND
ON/OFF
MAX863
13 LBO
12 FB2
11 SHDN1
10 CS2
9
EXT2
QSOP
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
MAX863
ABSOLUTE MAXIMUM RATINGS
V
DD
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 (V
DD
+ 0.3V)
FB1, FB2, CS1, CS2, SEL,
LBI, BOOT to GND.................................-0.3V to (V
DD
+ 0.3V)
LBO Continuous Output Current.........................................15mA
EXT1, EXT2 Continuous Output Current .............................50mA
Continuous Power Dissipation (T
A
= +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
(V
DD
= +5V, I
LOAD
= 0mA,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
V
DD
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
I
LBO
V
LBO,L
V
LBO
= 11V, V
LBI
> 1.275V
I
LBO
,
SINK
= 1mA, V
LBI
< 1.225V
0.1
t
ON
t
OFF
C
LOAD
= 1nF, 10% to 90%
14
1.6
V
FB
, V
LBI
I
FB
, I
LBI
V
IH
V
IL
I
I
V
CS
2.7V < V
DD
< 11V
V
DD
= 1.5V
2.7V < V
DD
< 11V
V
DD
= 1.5V
Logic input = V
DD
or GND
85
100
1
17.5
2
50
5
1
0.4
1.6
0.7 x V
DD
0.4
0.2 x V
DD
1
115
25
22
2.4
SYMBOL
V
DD
V
OUT1
(Note 2)
FB1 = V
DD
FB1 = GND
SHDN1
=
SHDN2
= V
DD
, measured from V
DD
I
DD
I
DD,
SHDN
SHDN1
= V
DD
,
SHDN2
= GND,
measured from V
DD
SHDN1
=
SHDN2
= GND
V
IN
= 3.3V, V
OUT1
= 5V,
I
LOAD
= 0mA to 500mA, Figure 2
V
IN
= 2.7V to 5V, V
OUT1
= 5V,
I
LOAD
= 300mA, Figure 2
1.225
40
8
1.25
2
1.275
10
CONDITIONS
V
DD
= OUT1 = BOOT (Note 1)
MIN
1.5
2.7
3.2
4.85
3.3
5
50
35
TYP
MAX
11
11
3.4
5.15
85
60
1
µA
µA
mV/A
mV/V
V
nA
V
V
µA
mV
µA
µs
µs
ns
Ω
µA
V
UNITS
V
V
2
_______________________________________________________________________________________
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
ELECTRICAL CHARACTERISTICS
(V
DD
= +5V, I
LOAD
= 0mA,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 6)
PARAMETER
V
DD
Input Voltage
OUT1 Output Voltage
(Note 3)
Quiescent Current
Shutdown Current
FB1, FB2 Threshold Voltage
CS1, CS2 Threshold Voltage
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
SYMBOL
V
DD
V
OUT1
(Note 2)
FB1 = V
DD
FB1 = GND
SHDN1
=
SHDN2
= V
DD
, measured from V
DD
I
DD
I
DD,
SHDN
V
FB
V
CS
SHDN1
= V
DD
,
SHDN2
= GND,
measured from V
DD
SHDN1
=
SHDN2
= GND
1.21
85
CONDITIONS
V
DD
= OUT1 (Note 1)
MIN
1.6
2.8
3.15
4.8
TYP
MAX
11
11
3.45
5.2
85
60
1
1.285
115
µA
µA
V
mV
UNITS
V
V
MAX863
When bootstrapped, an internal low-voltage oscillator drives the EXT1 pin rail-to-rail for low supply voltages.
For non-bootstrapped operation, V
DD
> 2.7V is required to allow valid operation of all internal circuitry.
For adjustable output voltages, see the
Set the Output Voltage
section.
Measured with LBI falling. Typical hysteresis is 15mV.
EXT1 and EXT2 swing from V
DD
to GND.
Specifications to -40°C are guaranteed by design and not production tested.
__________________________________________Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(V
OUT1
= 3.3V, BOOTSTRAPPED)
MAX863 toc01
EFFICIENCY vs. OUTPUT CURRENT
(V
OUT1
= 5.0V, BOOTSTRAPPED)
MAX863 toc02
EFFICIENCY vs. OUTPUT CURRENT
(V
OUT1
= 5.0V, NON-BOOTSTRAPPED)
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
V
OUT1
= 5.0V
A: V
IN
= 2.7V
B: V
IN
= 3.3V
C: V
IN
= 3.6V
D: V
IN
= 4.0V
100
1000
A
B
D
MAX863 toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
1000
OUTPUT CURRENT (mA)
V
OUT1
= 3.3V
A: V
IN
= 1.5V
B: V
IN
= 2.4V
C: V
IN
= 2.7V
B
A
C
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
B
A
C
100
F
C
D
E
V
OUT1
= 5.0V
A: V
IN
= 1.5V
B: V
IN
= 2.4V
C: V
IN
= 2.7V
D: V
IN
= 3.3V
E: V
IN
= 3.6V
F: V
IN
= 4.0V
100
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
_______________________________________________________________________________________
3
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
MAX863
____________________________Typical Operating Characteristics (continued)
(T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. OUTPUT CURRENT
(V
OUT1
= 12V, NON-BOOTSTRAPPED)
MAX863 toc04
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
100
A
V
OUT1
= 5.0V
A: V
IN
= 2.7V
B: V
IN
= 3.3V
C: V
IN
= 3.6V
D: V
IN
= 4.0V
E: V
IN
= 6.0V
B
C
D
E
BOOTSTRAPPED-MODE MINIMUM
START-UP INPUT VOLTAGE
vs. OUTPUT CURRENT
MAX863toc05
3.5
3.0
V
OUT1
= 5V
2.5
2.0
1.5
1.0
0.5
V
OUT1
= 3.3V
START-UP INPUT VOLTAGE (V)
1000
1
1
10
100
1000
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
V
DD
CURRENT
vs. V
DD
VOLTAGE
MAX863 toc15
60
50
V
DD
CURRENT (µA)
40
30
20
10
0
0
2
4
6
8
10
BOTH ON
EXT RISE AND FALL TIMES vs.
SUPPLY VOLTAGE AND MOSFET CAPACITANCE
C,1
C,2
A: 470pF
B: 1.0nF
C: 2.2nF
1: RISE
2: FALL
MAX863 toc07
140
120
RISE/FALL TIME (ns)
100
80
60
40
A,2
20
B,2
A,1
B,1
CONVERTER 1 ON
CONVERTER 2 ON
12
0
0
2
4
6
8
10
12
SUPPLY VOLTAGE (V)
Cond Single 5V
V
DD
VOLTAGE (V)
Cond: Single +5V
LOAD-TRANSIENT RESPONSE
MAX863 toc08
RESPONSE ENTERING/
EXITING SHUTDOWN (BOOTSTRAPPED)
A
LINE-TRANSIENT RESPONSE
MAX863 toc09
MAX863 toc10
A
B
C
3.3V
A
B
C
B
100µs/div
V
OUT1
= 3.3V, I
OUT1
= 100mA TO 600mA
A: V
OUT1
, 100mV/div, 3.3V DC OFFSET
B: I
OUT1
, 200mA/div
200µs/div
V
OUT1
= 3.3V, I
OUT1
= 100mA, V
IN
= 2.4V
A: SHDN1, 5V/div
B: INDUCTOR CURRENT, 2A/div
C: V
OUT1
, 3.3V OFFSET, 500mV/div
500µs/div
V
OUT1
= 5V, I
OUT1
= 800mA
A: V
IN
= 2.7V TO 3.7V, 500mV/div
B: V
OUT1
, AC COUPLED, 50mV/div
C: INDUCTOR CURRENT, 2A/div
0A
4
_______________________________________________________________________________________
Dual, High-Efficiency, PFM, Step-Up
DC-DC Controller
______________________________________________________________Pin Description
PIN
1
2
3
NAME
SENSE1
V
DD
FB1
FUNCTION
Feedback Input for DC-DC Controller 1 in Fixed-Output Mode
IC Power-Supply Input
Adjustable Feedback and Preset Output Voltage Selection Input for DC-DC Controller 1. Connect to V
DD
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
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, V
DD
must be connected to OUT1.
Input to the Current-Sense Comparator of DC-DC Controller 1
Gate-Drive Output of DC-DC Controller 1. Drives an external N-channel power MOSFET.
Analog Ground for Internal Reference, Feedback, and Control Circuits
High-Current Ground Return for Internal MOSFET Drivers
Gate-Drive Output of DC-DC Controller 2. Drives an external N-channel power MOSFET.
Input to the Current-Sense Amplifier of DC-DC Controller 2
Active-Low Shutdown Input for DC-DC Controller 1. Connect to V
DD
for normal operation.
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.
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.
Low-Battery Comparator Input. When the voltage on LBI drops below 1.25V, LBO sinks current. If unused,
connect to GND.
Active-Low Shutdown Input for DC-DC Controller 2. Connect to V
DD
for normal operation.
Reference Bypass Input. Connect a 0.1µF ceramic capacitor from REF to GND.
MAX863
4
BOOT
5
6
7
8
9
10
11
12
13
14
15
16
CS1
EXT1
GND
PGND
EXT2
CS2
SHDN1
FB2
LBO
LBI
SHDN2
REF
_______________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
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