19-1381; Rev 0; 7/98
KIT
ATION
EVALU
BLE
AVAILA
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
General Description
Features
o
0.87V Guaranteed Start-Up
o
Up to 90% Efficiency
o
Built-In Synchronous Rectifier (no external diode)
o
Ultra-Small µMAX Package, 1.1mm High
o
37µA Quiescent Current (85µA from 1.5V battery)
o
2µA Logic-Controlled Shutdown
o
Power-Fail Detector
o
Dual Mode™ Output: Fixed 3.3V
Adjustable 2V to 5.5V
o
45mA Output Current at 3.3V for 1-Cell Input
o
90mA Output Current at 3.3V for 2-Cell Input
o
Inductor-Damping Switch Suppresses EMI
MAX1678
The MAX1678 is a high-efficiency, low-voltage, syn-
chronous-rectified, step-up DC-DC converter intended
for use in devices powered by 1 to 3-cell alkaline,
NiMH, or NiCd batteries or a 1-cell lithium battery. It
guarantees a 0.87V start-up voltage and features a low
37µA quiescent supply current.
The device includes a 1Ω, N-channel MOSFET power
switch, a synchronous rectifier that acts as the catch
diode, a reference, pulse-frequency-modulation (PFM)
control circuitry, and circuitry to reduce inductor ring-
ing—all in an ultra-small, 1.1mm-high µMAX package.
The output voltage is preset to 3.3V or can be adjusted
from +2V to +5.5V using only two resistors. Efficiencies
up to 90% are achieved for loads up to 50mA. The
device also features an independent undervoltage
comparator (PFI/PFO) and a logic-controlled 2µA shut-
down mode.
Applications
Pagers
Remote Controls
Pointing Devices
Personal Medical Monitors
Single-Cell Battery-Powered Devices
PART
MAX1678EUA
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
8 µMAX
Note: To order these devices shipped in tape-and-reel, add a -T
to the part number.
Typical Operating Circuit
Pin Configuration
INPUT
0.87V TO V
OUT
LX
OUT
OUTPUT
3.3V
TOP VIEW
MAX1678
BATT
ON
OFF
LOW-BATTERY
DETECTOR INPUT
SHDN
PFI
GND
PFO
FB
LOW-BATTERY
DETECTOR OUTPUT
BATT
PFI
PFO
SHDN
1
2
3
4
8
OUT
LX
GND
FB
MAX1678
7
6
5
µMAX
Dual Mode is a trademark of Maxim Integrated Products.
________________________________________________________________
Maxim Integrated Products
1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 408-737-7600 ext. 3468.
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
MAX1678
ABSOLUTE MAXIMUM RATINGS
BATT, OUT,LX,
SHDN
to GND ..............................-0.3V to +6.0V
OUT, LX Current.......................................................................1A
FB, PFI, PFO to GND ................................-0.3V to (V
OUT
+ 0.3V)
Reverse Battery Current (T
A
= +25°C) (Note 1) ...............220mA
Continuous Power Dissipation (T
A
= +70°C)
µMAX (derate 4.1mW/°C above +70°C) .......................330mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +165°C
Lead Temperature (soldering, 10sec) .............................+300°C
Note 1:
The reverse battery current is measured from the
Typical Operating Circuit’s
input terminal to GND when the battery is con-
nected backward. A reverse current of 220mA will not exceed package dissipation limits but, if left for an extended time
(more than 10 minutes), may degrade performance.
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
BATT
= V
SHDN
= 1.3V, I
LOAD
= 0, FB = GND,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Minimum Operating Input
Voltage
Maximum Operating Input
Voltage
Start-Up Voltage (Note 2)
Start-Up Voltage Tempco
Output Voltage (Fixed Mode)
Output Voltage Range
(Adjustable Mode)
FB Set Voltage
N-Channel On-Resistance
P-Channel On-Resistance
P-Channel Catch Diode Voltage
Maximum Peak LX Current
On-Time Constant
Quiescent Current into OUT
Quiescent Current into BATT
Shutdown Current into OUT
Shutdown Current into BATT
Efficiency
FB Input Current
PFI Trip Voltage
PFI Input Current
PFO Low Output Voltage
PFO Leakage Current
SHDN
Input Low Voltage
SHDN
Input High Voltage
SHDN
Input Current
V
IL
V
IH
SHDN
= GND or BATT
0.8 x V
BATT
0.1
10
V
OL
V
IL,PFI
I
LX(MAX)
K
I
Q,OUT
I
Q,BATT
I
SHDN,OUT
I
SHDN,BATT
η
V
OUT
= 3.5V
V
BATT
= 1V
I
LOAD
= 20mA, V
BATT
= 2.5V (Figure 7)
V
FB
= 1.3V
Falling PFI hysteresis 2%
V
PFI
= 650mV
V
PFI
= 0, V
OUT
= 3.3V, I
SINK
= 1mA
V
PFI
= 650mV, V
PFO
= 6V
590
0.9V < V
BATT
< 3.3V (t
ON
= K / V
BATT
)
V
OUT
= 3.5V
5.60
V
FB
V
OUT
V
FB
< 0.1V
External feedback
External feedback
V
OUT
= 3.3V
V
OUT
= 3.3V
I
DIODE
= 100mA, P-channel switch off
3.16
2.0
1.19
1.23
1
1.5
0.8
550
8
37
4
0.1
2
90
0.1
614
0.1
0.04
0.01
10
632
10
0.4
1
11.2
65
8
1
3.5
SYMBOL
V
BATT(MIN)
V
BATT(MAX)
R
L
= 3kΩ, T
A
= +25°C
0.87
-2
3.3
3.44
5.5
1.26
1.5
2.2
CONDITIONS
MIN
TYP
0.7
5.5
MAX
UNITS
V
V
V
mV/°C
V
V
V
Ω
Ω
V
mA
V-µs
µA
µA
µA
µA
%
nA
mV
nA
V
µA
V
V
nA
0.2 x V
BATT
2
_______________________________________________________________________________________
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
ELECTRICAL CHARACTERISTICS
(V
BATT
= V
SHDN
= 1.3V, I
LOAD
= 0, FB = GND,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 3)
PARAMETER
Maximum Operating Input
Voltage
Output Voltage (Fixed Mode)
Output Voltage Range
(Adjustable Mode)
FB Set Voltage
N-Channel On-Resistance
P-Channel On-Resistance
On-Time Constant
Quiescent Current into OUT
Quiescent Current into BATT
Shutdown Current into OUT
Shutdown Current into BATT
FB Input Current
PFI Trip Voltage
PFI Input Current
PFO Low Output Voltage
PFO Leakage Current
SHDN
Input Low Voltage
SHDN
Input High Voltage
SHDN
Input Current
V
IL
V
IH
SHDN
= GND or BATT
0.8 x V
BATT
10
V
OL
V
IL,PFI
K
I
Q,OUT
I
Q,BATT
I
SHDN,OUT
I
SHDN,BATT
V
OUT
= 3.5V
V
BATT
= 1V
V
FB
= 1.3V
Falling PFI hysteresis 2%
V
PFI
= 650mV
V
PFI
= 0, V
OUT
= 3.3V, I
SINK
= 1mA
V
PFI
= 650mV, V
PFO
= 6V
580
V
FB
SYMBOL
V
BATT(MAX)
V
OUT
V
FB
< 0.1V
External feedback
External feedback
V
OUT
= 3.3V
V
OUT
= 3.3V
0.9V < V
BATT
< 3.3V (t
ON
= K / V
BATT
)
V
OUT
= 3.5V
5.60
3.12
2.0
1.17
CONDITIONS
MIN
MAX
5.5
3.48
5.5
1.28
1.5
2.2
11.2
65
8
1
3.5
10
642
10
0.4
1
0.2 x V
BATT
UNITS
V
V
V
V
Ω
Ω
V-µs
µA
µA
µA
µA
nA
mV
nA
V
µA
V
V
nA
MAX1678
3
Note 2:
Start-up is guaranteed by correlation to measurements of device parameters (i.e., switch on-resistance, on-time, off-time,
and output voltage trip point).
Note 3:
Specifications to -40°C are guaranteed by design and not production tested.
_______________________________________________________________________________________
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
MAX1678
Typical Operating Characteristics
(Circuit of Figure 7 (Fixed Mode, 3.3V) or Figure 8 (Adjustable Mode), T
A
= +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 2.4V, L1 = 22µH)
MAX1678-01
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 2.4V, L1 = SUMIDA 47µH)
MAX1678-02
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 2.4V, L1 = TDK 47µH)
90
80
V
IN
= 2.0V
V
IN
= 1.5V
MAX1678-03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
L1 = 22µH
SUMIDA CD43-220
R1 = 200kΩ, R2 = 200kΩ
V
IN
= 0.85V
V
IN
= 1.2V
V
IN
= 1.5V
V
IN
= 2.0V
100
90
80
EFFICIENCY (%)
V
IN
= 1.2V
V
IN
= 0.85V
V
IN
= 1.5V
V
IN
= 2.0V
100
60
50
40
30
20
10
0
0.01
0.1
EFFICIENCY (%)
70
70
60
50
40
30
V
IN
= 0.85V
V
IN
= 1.2V
L1 = 47µH
SUMIDA CD43-470
R1 = 200kΩ, R2 = 200kΩ
1
10
100 200
20
10
0
0.01
0.1
L1 = 47µH
TDK NLC453232T-470K
R1 = 200kΩ, R2 = 200kΩ
1
10
100 200
100 200
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V, L1 = 22µH)
MAX1678-04
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V, L1 = SUMIDA 47µH)
MAX1678-05
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V, L1 = TDK 47µH)
90
80
V
IN
= 2.5V
V
IN
= 1.5V
V
IN
= 2.0V
MAX1678-06
MAX1678-09
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
L1 = 22µH
SUMIDA CD43-220
FB = GND
V
IN
= 0.85V
V
IN
= 1.2V
V
IN
= 2.5V
V
IN
= 2.0V
V
IN
= 1.5V
100
90
80
EFFICIENCY (%)
V
IN
= 2.5V
V
IN
= 2.0V
100
60
50
40
30
20
10
0
0.01
0.1
V
IN
= 0.85V V = 1.5V
IN
EFFICIENCY (%)
70
V
IN
= 1.2V
70
60
50
40
30
V
IN
= 0.85V
V
IN
= 1.2V
L1 = 47µH
SUMIDA CD43-470
FB = GND
1
10
100 200
20
10
0
0.01
0.1
1
L1 = 47µH
TDK NLC453232T-470K
FB = GND
10
100 200
100 200
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5.0V, L1 = 22µH)
MAX1678-07
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5.0V, L1 = SUMIDA 47µH)
90
80
EFFICIENCY (%)
V
IN
= 4.5V
V
IN
= 3.0V
V
IN
= 2.0V
V
IN
= 1.2V
V
IN
= 0.85V
EFFICIENCY (%)
MAX1678-08
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5.0V, L1 = TDK 47µH)
100
90
80
70
60
50
40
30
V
IN
= 1.2V
V
IN
= 0.85V
V
IN
= 2.0V
V
IN
= 4.5V
V
IN
= 3.0V
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
0.01
0.1
1
10
L1 = 22µH
SUMIDA CD43-220
R1 = 619kΩ, R2 = 200kΩ
V
IN
= 0.85V
V
IN
= 1.2V
V
IN
= 4.5V
V
IN
= 3.0V
V
IN
= 2.0V
100
70
60
50
40
30
20
10
0
0.01
0.1
L1 = 47µH
SUMIDA CD43-470
R1 = 619kΩ, R2 = 200kΩ
1
10
100 200
20
10
0
0.01
0.1
L1 = 47µH
TDK NLC453232-470K
R1 = 619kΩ, R2 = 200kΩ
1
10
100 200
100 200
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
4
_______________________________________________________________________________________
1-Cell to 2-Cell, Low-Noise,
High-Efficiency, Step-Up DC-DC Converter
Typical Operating Characteristics (continued)
(Circuit of Figure 7 (Fixed Mode, 3.3V) or Figure 8 (Adjustable Mode), T
A
= +25°C, unless otherwise noted.)
NO-LOAD BATTERY CURRENT
vs. INPUT VOLTAGE
MAX1678-11
MAX1678
EFFICIENCY WITH DIFFERENT INDUCTORS
85
80
EFFICIENCY (%)
75
DS1608C-473
CD43-470
22µH NLC453232T-220K
47µH NLC453232T-470K
BATT AND OUT QUIESCENT CURRENT
vs. TEMPERATURE
40
QUIESCENT CURRENT (µA)
35
30
25
20
15
10
5
0
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
I
BATT
V
BATT
= 1.3V
V
OUT
= 3.6V
FB = GND
MAX1678-12
NO-LOAD BATTERY CURRENT (µA)
V
BATT
= 1.2V
V
OUT
= 3.3V
I
LOAD
= 20mA
MAX1678-10
90
1000
V
OUT
= 5.0V
R1 = 3MΩ, R2 = 1MΩ
V
OUT
= 3.0V
FB = GND
100
45
I
OUT
70
65
60
DT1608C-223
LQH4N470K
CD43-220
LQH3C470K
47µH
22µH
47µH
22µH
47µH
47µH
55
50
10
L1 = 47µH
SUMIDA CD43-470
V
OUT
= 2.4V
R1 = 1MΩ, R2 = 1MΩ
COILCRAFT SUMIDA
MURATA
TDK
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
SHUTDOWN BATTERY CURRENT
vs. INPUT VOLTAGE
MAX1678-13
ON-TIME CONSTANT (K)
vs. TEMPERATURE
MAX1678-14
MINIMUM START-UP INPUT VOLTAGE
vs. LOAD CURRENT
L1 = 47µH
SUMIDA CD43-470
3.3V FIXED MODE
WITHOUT
DIODE
MAX1678-15
12
SHUTDOWN BATTERY CURRENT (µA)
10
8
6
4
2
0
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
3.3V FIXED MODE
L1 = 47µH
SUMIDA CD43-470
9.0
V
BATT
= 1.3V
8.8
ON-TIME CONSTANT (V-µs)
8.6
8.4
8.2
8.0
7.8
7.6
-40
-20
0
20
40
60
80
1.3
1.2
START-UP INPUT VOLTAGE (V)
1.1
1.0
0.9
0.8
0.7
0.6
WITH EXTERNAL
SCHOTTKY DIODE
(FIGURE 3)
100
0
5
10
15
20
25
30
35
TEMPERATURE (°C)
LOAD CURRENT (mA)
MAXIMUM LOAD CURRENT
vs. INPUT VOLTAGE
(L1 = 22µH)
MAX1678-16
MAXIMUM LOAD CURRENT
vs. INPUT VOLTAGE
(L1 = SUMIDA 47µH)
MAX1678-17
MAXIMUM LOAD CURRENT
vs. INPUT VOLTAGE
(L1 = TDK 47µH)
L1 = 47µH
TDK NLC453232T-470K
MAX1678-18
140
MAXIMUM LOAD CURRENT (mA)
120
100
80
60
40
20
0
V
OUT
= 3.3V
V
OUT
= 5.0V
L1 = 22µH
SUMIDA CD43-220
V
OUT
= 2.4V
140
MAXIMUM LOAD CURRENT (mA)
120
100
80
60
40
20
0
V
OUT
= 2.4V
V
OUT
= 5.0V
L1 = 47µH
SUMIDA CD43-470
140
MAXIMUM LOAD CURRENT (mA)
120
100
80
60
V
OUT
= 2.4V
40
20
0
V
OUT
= 5.0V
V
OUT
= 3.3V
V
OUT
= 3.3V
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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