19-1403; Rev 1; 3/01
KIT
ATION
EVALU
E
BL
AVAILA
Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
General Description
Features
o
No External FETs Required
o
Main Output
Up to 350mA for Logic Supply
Fixed 3.3V or Adjustable (2.5V to 5.5V)
Synchronous Rectification for High Efficiency
(up to 95%)
300kHz (200kHz to 400kHz Synchronizable)
Fixed-Frequency PWM Operation
o
Secondary Output
Up to +28V or -28V for LCD Bias
Programmable Current Limit
o
0.7V to 5.5V Input Voltage Range
o
20µA Quiescent Current
o
1µA Shutdown Current
o
Low-Battery Comparator
o
Small 16-Pin QSOP Package
MAX1677
The MAX1677 is a compact, high-efficiency, dual-out-
put boost converter for portable devices needing two
regulated supplies, typically for logic and liquid crystal
displays (LCDs). Operation with inputs as low as 0.7V
allows the MAX1677 to accept 1, 2, or 3-cell alkaline,
NiCd, or NiMH batteries as well as 1-cell lithium-ion bat-
teries. The device requires no external FETs and can
maintain regulation while consuming only 20µA, making
it ideal for hand-held pen-input and PDA devices oper-
ating with low-current “sleep” states.
The MAX1677’s primary regulator supplies up to
350mA at either a factory-preset 3.3V or an adjustable
2.5V to 5.5V output. On-chip synchronous rectification
provides efficiencies up to 95%. 300kHz (or externally
clocked) pulse-width-modulation (PWM) operation is
particularly suitable for applications needing low noise,
such as those with wireless features. The primary con-
verter also features pin-selectable pulse-frequency-
modulation (PFM) operation that consumes only 20µA.
A 1µA shutdown state also minimizes battery drain.
The MAX1677’s secondary step-up converter supplies up
to +28V or -28V for LCD bias, varactor tuning, or other
high-voltage, low-current functions. Other MAX1677 fea-
tures include precision reference, logic control inputs for
both regulators, and an uncommitted comparator for
low-battery detection or a reset function. The MAX1677
is supplied in Maxim’s compact 16-pin QSOP package,
which occupies no more space than a standard SO-8.
Ordering Information
PART
MAX1677EEE
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
Typical Operating Circuit
Applications
PDAs
Hand-Held Terminals
Portable Phones
Portable Instruments
V
IN =
0.7V to 5.5V
(UP TO MAIN
OUT
)
LX
POUT
3.3V MAIN
BOOST OUTPUT
Pin Configuration
TOP VIEW
OUT 1
FB 2
LBI 3
LBO 4
CLK/SEL 5
LCDON 6
LCDPOL 7
REF 8
16 POUT
15 LX
14 PGND
OFF
PWM
PFM
ON
OFF
11 ON
10 LCDFB
9
GND
-VE OUT
+VE OUT
ON
MAX1677
LCDLX
LBI
OUT
LBO
LCDFB
LCDON
CLK/SEL
ON
LCDPOL
PGND
FB
LCDGND
GND
REF
±28V
LCD
BOOST
OUTPUT
MAX1677
13 LCDGND
12 LCDLX
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.
Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
MAX1677
ABSOLUTE MAXIMUM RATINGS
OUT, LCDON, ON, POUT, LBI,
LBO,
LX to GND .............................................................-0.3V to +6V
CLK/SEL, LCDPOL, REF, LCDFB,
FB to GND .............................................-0.3V to (V
OUT
+ 0.3V)
LCDLX to GND .......................................................-0.3V to +30V
PGND, LCDGND to GND ......................................-0.3V to +0.3V
POUT to OUT.........................................................-0.3V to +0.3V
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........696mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +160°C
Lead Temperature (soldering, 10s) .................................+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
OUT
= 3.3V, C
REF
= 0.1µF, POUT = OUT,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
GENERAL
Input Voltage Range
Minimum Startup Voltage
Reference Voltage
Reference Load Regulation
Reference Line Rejection
Supply Current
Main DC On, LCD Off
Supply Current All On,
Main DC-DC in PFM Mode
Supply Current All On,
Main DC-DC in PWM Mode
Supply Current in Shutdown
MAIN BOOST DC-DC
Output Voltage
FB Regulation Voltage
FB Input Current
Output Voltage Adjustment
Range
Startup to Normal Mode
Transition Voltage (Note 4)
Line Regulation
Load Regulation
Frequency in Startup Mode
LX Leakage Current
f
STARTUP
I
LX (LEAK)
V
LOCKOUT
I
OUT
= 150mA, V
IN
= 2V to 3V
CLK/SEL = OUT, V
IN
= 2.4V,
I
LOAD
= 10mA to 200mA
V
OUT
= 15V
40
0.2
V
OUT
V
FB (REG)
I
FB
FB = GND, 0
≤
I
LX
≤
350mA,
CLK/SEL = OUT (Note 3)
Adjustable mode, CLK/SEL = OUT (Note 3)
V
FB
= 1.3V
2.5
2.1
0.6
1
300
5
3.20
1.225
3.30
1.25
0.02
3.43
1.275
50
5.5
2.4
V
V
nA
V
V
%
%
kHz
µA
I
LCDOFF
I
PFM
I
PWM
V
IN
V
STARTUP
V
REF
(Note 1)
T
A
= +25°C, I
LOAD
< 1mA
I
REF
= 0
I
REF
= 0 to 50µA (Note 2)
V
OUT
= 2.5V to 5.5V
No load, current into OUT
No load, current into OUT
No load, current into OUT
1.23
0.7
0.9
1.25
2
0.2
20
35
115
0.3
5.5
1.1
1.27
15
5
40
60
300
5
V
V
V
mV
mV
µA
µA
µA
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
ELECTRICAL CHARACTERISTICS (continued)
(V
OUT
= 3.3V, C
REF
= 0.1µF, POUT = OUT,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
LX On-Resistance
LX Current Limit
P-Channel Synchronous Rectifier
Turn-Off Current in PFM Mode
Internal Oscillator
Oscillator Maximum Duty Cycle
External Clock Frequency
Range
LOGIC AND CONTROL INPUTS
Input Leakage Current
ON Input Threshold
LCDON, LCDPOL, CLK/SEL
Input Threshold
LBI Falling Threshold
LBI Hysteresis
LBO
Output Low Voltage
LBI Input Bias Current
LBO
Leakage Current
LCDLX Voltage
LCDPOL = OUT or GND
LCDLX Switch Current Limit
LCDLX Switch Resistance
LCDLX Leakage Current
LCDFB Set Point
LCDFB Input Bias Current
LCD Line Regulation
LCD Load Regulation
Maximum LCDLX On-Time
Minimum LCDLX Off-Time
LCDFB Voltage for
Startup Mode
t
ON LCD
Operating mode
Start-up mode (positive or negative)
LCDPOL = OUT
LCDPOL = GND
I
LOAD
= 5mA, V
IN
= 1.2V to 3.6V,
Figure 2
I
LOAD
= 0 to 5mA, V
IN
= 2.4V,
Figure 2
3.4
0.8
3.0
0.1
0.5
4.3
1
4.0
0.75
0.5
5.2
1.2
5.0
R
LCDLX
LCDPOL connected to OUT or GND through
50kΩ
V
OUT
= 3.3V
V
LCDLX
= 28V
Positive LCD, LCDPOL = OUT
Negative LCD, LCDPOL = GND
1.225
-15
1.25
0
300
150
350
225
1.0
V
LBO(LO)
I
LBI(BIAS)
I
LBO(LEAK)
V
LBO
= 5.5V
Sink current = 1mA
V
ON(LOW)
V
ON(HIGH)
V
IL
V
IH
V
LBI(TH)
ON, LCDON, LCDPOL, CLK/SEL
1.1V < V
OUT
< 5.5V
V
OUT
> 2.5V
0.8V
OUT
0.2V
OUT
0.8V
OUT
599
614
1
0.1
50
1
28
450
300
1.4
1
1.275
15
50
mA
Ω
µA
V
mV
nA
%/V
%
µs
µs
V
629
1
0.2V
OUT
µA
V
V
mV
%
V
nA
µA
V
f
D
CLK/SEL = OUT
SYMBOL
R
LX(ON)N
R
LX(ON)P
I
LX(PWM)
I
LX(PFM)
N-channel
P-channel
N-channel PWM mode
N-channel PFM mode
550
250
40
240
80
200
CONDITIONS
MIN
TYP
0.22
0.4
670
350
90
300
85
MAX
0.5
1.0
800
450
140
360
90
400
UNITS
Ω
mA
mA
kHz
%
kHz
MAX1677
3
_______________________________________________________________________________________
Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
MAX1677
ELECTRICAL CHARACTERISTICS
(V
OUT
= 3.3V, C
REF
= 0.1µF, POUT = OUT,
T
A
= -40°C to +85°C,
unless otherwise noted. ) (Note 5)
PARAMETER
GENERAL
Supply Current
Main DC On, LCD Off
Supply Current All On,
Main DC-DC in PFM Mode
Supply Current All On,
Main DC-DC in PWM Mode
Supply Current in Shutdown
MAIN
Output Voltage
FB Regulation Voltage
Startup to Normal Mode Transition
Voltage (Note 4)
LX Leakage Current
LX Current Limit
Internal Oscillator
External Clock Frequency Range
LOGIC
ON Input Threshold
LCDON, LCDPOL, CLK/SEL
Input Threshold
LBI Falling Threshold
LBO
Output Low Voltage
LCD BIAS DC-DC
LCDPOL = OUT or GND
LCDLX Switch Current Limit
LCDPOL connected to OUT or GND
through 50kΩ
Positive LCD, LCDPOL = OUT
Negative LCD, LCDPOL = GND
300
150
1.22
-20
450
300
1.28
+20
mA
V
mV
V
ON(LOW)
V
ON(HIGH)
V
IL
V
IH
V
LBI(TH)
V
LBO(LO)
Sink current = 1mA
0.8V
OUT
599
629
0.1
1.1V < V
OUT
< 5.5V
0.2V
OUT
0.8V
OUT
0.2V
OUT
V
V
mV
V
V
OUT
V
FB(REG)
V
LOCKOUT
I
LX(LEAK)
I
LX(PWM)
I
LX(PFM)
f
N-channel PWM mode
N-channel PFM mode
CLK/SEL = OUT
550
250
240
200
FB = GND, 0
≤
I
LX
≤
350mA,
CLK/SEL = OUT (Note 3)
Adjustable mode, CLK/SEL = OUT (Note 3)
3.17
1.22
2.1
3.46
1.28
2.4
5
900
500
360
400
V
V
V
µA
mA
kHz
kHz
I
LCDOFF
I
PFM
I
PWM
No load, current into OUT
No load, current into OUT
No load, current into OUT
40
60
300
5
µA
µA
µA
µA
SYMBOL
CONDITIONS
MIN
MAX
UNITS
LCDFB Set Point
Note 1:
The MAX1677 operates in bootstrap mode (operates from the output voltage). Once started, it will operate down to 0.7V
input. If V
IN
exceeds the set V
OUT
, V
OUT
will follow one diode drop below V
IN
.
Note 2:
C
REF
= 0.22µF for applications where I
REF
> 10µA.
Note 3:
In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than in low-noise mode (CLK/SEL = OUT or
synchronized).
Note 4:
The device is in a startup mode when V
OUT
is below this value.
Note 5:
Specifications to -40°C are guaranteed by design and not production tested.
4
_______________________________________________________________________________________
Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
MAX1677
Typical Operating Characteristics
(Circuits of Figures 2 and 3, T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V)
MAX1677-01
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5V)
MAX1677-02
MAXIMUM LOAD CURRENT
vs. BATTERY INPUT VOLTAGE
(PWM MODE)
MAX1677-03
100
PFM MODE
A = V
IN
= 2.4V
B = V
IN
= 1.2V
90
EFFICIENCY (%)
A
C
100
D
A
700
600
LOAD CURENT (mA)
500
400
300
200
100
0
V
OUT
= 3.3V
V
OUT
= 5V
80
EFFICIENCY (%)
E
F
60
80
B
D
B
40
C
PWM MODE
A: V
IN
= 3.6V
B: V
IN
= 2.4V
C: V
IN
= 1.2V
PFM MODE
D: V
IN
= 3.6V
E: V
IN
= 2.4V
F: V
IN
= 1.2V
70
PWM MODE
C = 2.4V
D = 1.2V
60
0.1
1
10
100
1000
LOAD CURRENT (mA)
20
0
0.1
1
10
100
1000
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
EFFICIENCY vs. LOAD CURRENT
(LCD V
OUT
= 12V)
MAX1677-04
EFFICIENCY vs. LOAD CURRENT
(LCD V
OUT
= 20V)
CIRCUIT OF FIGURE 2
A: V
IN
= 3.6V
B: V
IN
= 2.4V
C: V
IN
= 1.2V
MAX1677-05
REFERENCE VOLTAGE
vs. REFERENCE CURRENT
MAX1677-06
100
90
EFFICIENCY (%)
80
A
70
60
50
40
0.1
1
10
B
C
CIRCUIT OF FIGURE 2
A: V
IN
= 3.6V
B: V
IN
= 2.4V
C: V
IN
= 1.2V
100
1.2550
REFERENCE VOLTAGE (V)
90
EFFICIENCY (%)
1.2525
80
A
B
60
C
50
1.2500
70
1.2475
1.2450
0.1
1
10
100
0
20
40
60
80
100
LOAD CURRENT (mA)
REFERENCE CURRENT (µA)
100
LOAD CURRENT (mA)
LOAD CURRENT
vs. STARTUP VOLTAGE
400
350
LOAD CURRENT (mA)
300
250
200
150
100
50
0
0
0.5
1.0
1.5
2.0
2.5
3.0
START-UP VOLTAGE (V)
PFM
V
OUT
= 3.3V
TESTED WITH
RESISTIVE LOAD
MAX1677-07
NO-LOAD SUPPLY CURRENT vs.
INPUT VOLTAGE (LCD OFF)
MAX1677-08
NO-LOAD SUPPLY CURRENT vs.
INPUT VOLTAGE (LCD ON)
1.0
0.9
SUPPLY CURRENT (mA)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
V
OUT
= 3.3V
PFM MODE
V
LCD
= -20V
MAX1677-09
450
0.20
0.18
0.16
SUPPLY CURRENT (mA)
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
0
0.5
1.0
1.5
2.0
2.5
3.0
V
OUT
= 3.3V
PFM MODE
LCD OFF
1.1
PWM
3.5
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
INPUT VOTAGE (V)
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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