19-1095; Rev 2; 12/97
1-Cell to 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters
General Description
The MAX848/MAX849 boost converters set a new stan-
dard of high efficiency and high integration for noise-
sensitive power-supply applications, such as portable
phones and small systems with RF data links. The heart
of the these devices is a synchronous boost-topology
regulator that generates a fixed 3.3V output (or 2.7V to
5.5V adjustable output) from one to three NiCd/NiMH
cells or one Li-Ion cell.
Synchronous rectification provides a 5% efficiency
improvement over similar nonsynchronous boost regu-
lators. In standby mode, pulse-skipping PFM operation
keeps the output voltage alive with only 150µW quies-
cent power consumption. Fixed-frequency PWM opera-
tion ensures that the switching noise spectrum is limited
to the 300kHz fundamental and its harmonics, allowing
easy post-filtering noise reduction. For even tighter
noise spectrum control, synchronize to a 200kHz to
400kHz external clock.
Battery monitoring is provided by a two-channel, volt-
age-to-frequency analog-to-digital converter (ADC).
One channel is intended for a single-cell battery input
(0.625V to 1.875V range), while the other channel is for
monitoring higher voltages (0V to 2.5V range).
Two control inputs are provided for push-on, push-off
control via a momentary pushbutton switch. Upon
power-up, an internal comparator monitors the output
voltage to generate a power-good output (POK).
The devices differ only in the current limit of the
N-channel MOSFET power switch: 0.8A for the
MAX848, and 1.4A for the MAX849.
Features
o
Up to 95% Efficiency
(see
Typical Output Selector Guide
below)
o
3.3V Dual Mode™ or 2.7V to 5.5V Adj. Output
o
0.7V to 5.5V Input Range
o
0.15mW Standby Mode
o
300kHz PWM Mode or Synchronizable
o
Two-Channel ADC with Serial Output
o
Power-Good Function
MAX848/MAX849
Applications
Digital Cordless Phones
Cellular Phones
Palmtop Computers
Local 3.3V to 5V Supplies
PCS Phones
Hand-Held Instruments
Personal Communicators
Ordering Information
PART
MAX848ESE
MAX849ESE
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 Narrow SO
16 Narrow SO
Typical Operating Circuit
INPUT
0.8V TO 5.5V
Typical Output Selector Guide
V
IN
(V)
0.9
1.2
2.4
2.7
3.6
V
OUT
(V)
3.3
5
3.3
5
3.3
5
3.3
5
5
MAX849 I
OUT
(mA)
100
70
300
200
750
500
800
600
1000
MAX848 I
OUT
(mA)
70
40
110
70
200
130
250
150
300
A/D CHANNEL 1 IN
A/D CHANNEL 2 IN
A/D CHANNEL SELECT
A/D OUTPUT
ON/OFF CONTROL
SYNC INPUT
AIN1
AIN2
AINSEL
MAX848
MAX849
LX
OUT
POUT
POK
FB
OUTPUT
DATA
ON1
ON2
CLK/SEL
POKIN
REF
GND
VOLTAGE MONITOR
OUTPUT
PGND
Pin Configuration appears at end of data sheet.
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 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters
MAX848/MAX849
ABSOLUTE MAXIMUM RATINGS
ON1,
ON2,
OUT, POUT to GND..................................-0.3V, +6V
PGND to GND ..........................................................-0.3V, +0.3V
LX to PGND ...............................................-0.3V, (V
POUT
+ 0.3V)
CLK/SEL, DATA, POKIN, REF,
AINSEL, AIN1, AIN2, FB, POK to GND .....-0.3V, (V
OUT
+ 0.3V)
Continuous Power Dissipation (T
A
= +70°C)
Narrow SO (derate 8.7mW/°C above +70°C) ................696mW
Operating Temperature Range
MAX848ESE/MAX849ESE .................................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature.........................................-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
OUT
= 3.6V, GND = PGND = CLK/SEL = ON1 =
ON2
= AINSEL = AIN1 = AIN2 = FB = POKIN, POUT = OUT,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Minimum Operating Voltage (Note 1)
REFERENCE
Reference Output Voltage
REF Load Regulation
REF Supply Rejection
DC-DC CONVERTER
Output Voltage (Note 2)
I
REF
= 0mA
-1µA < I
REF
< 50µA
2.5V < V
OUT
< 5V
V
FB
< 0.1V, CLK/SEL = OUT
V
OUT
= 3.3V
V
IN
= 1.2V
V
OUT
= 5V
V
OUT
= 3.3V
V
IN
= 2.4V
Output Current
V
OUT
= 5V
V
OUT
= 3.3V
V
IN
= 2.7V
V
OUT
= 5V
V
OUT
= 5V
FB Regulation Voltage
FB Input Current
Output Voltage Adjust Range
Output Voltage Lockout Range
Load Regulation (Note 4)
Minimum Start-Up Voltage (Note 5)
Frequency in Start-Up Mode
Operating Current in Shutdown
(Note 3)
CLK/SEL = OUT
I
LOAD
< 1mA, T
A
> +25°C
V
OUT
= 1.5V
Current into OUT pin, V
ON2
= 3.6V
40
4
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
MAX848
MAX849
3.17
1.23
CONDITIONS
MIN
TYP
0.7
1.25
5
0.2
3.34
110
300
70
200
200
750
130
500
250
600
150
800
300
1000
1.215
2.7
2.1
-1.6
0.9
1.1
300
20
1.240
1.265
200
5.5
2.4
V
nA
V
V
%
V
kHz
µA
mA
mA
1.27
15
5
3.40
MAX
UNITS
V
V
mV
mV
V
MAX848, V
IN
= 3.3V
MAX849, V
IN
= 3.6V
Adjustable output, CLK/SEL = OUT
V
FB
= 1.25V
2
_______________________________________________________________________________________
1-Cell to 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(V
OUT
= 3.6V, GND = PGND = CLK/SEL = ON1 =
ON2
= AINSEL = AIN1 = AIN2 = FB = POKIN, POUT = OUT,
T
A
= 0°C to +85°C,
unless otherwise noted.)
PARAMETER
Operating Current in Low-Power
Mode (Note 6)
Operating Current in Low-Noise
Mode (Note 6)
DC-DC SWITCHES
POUT Leakage Current
LX Leakage Current
Switch On-Resistance
V
LX
= 0V, V
ON2
= V
OUT
= 5.5V
V
LX
= V
ON2
= V
OUT
= 5.5V
N-channel
P-channel
CLK/SEL = OUT
N-Channel Current Limit
V
CLK/SEL
= 0V (Note 7)
ADC
Data Output Voltage Low
Data Output Voltage High
AIN1 Input Voltage Range
AIN2 Input Voltage Range
AIN1, AIN2 Input Current
Accuracy
POWER-GOOD
Internal Trip Level
External Trip Level
POK Low Voltage
POK High Leakage Current
POKIN Leakage Current
LOGIC AND CONTROL INPUTS
Input Low Voltage
Input High Voltage
Logic Input Current
Internal Oscillator Frequency
Oscillator Maximum Duty Cycle
External Clock Frequency Range
CLK/SEL Pulse Width
CLK/SEL Rise/Fall Time
Not tested
Not tested
1.2V < V
OUT
< 5.5V, ON1 and
ON2
(Note 8)
V
OUT
= 2.7V, AINSEL and CLK/SEL
1.2V < V
OUT
< 5.5V, ON1 and
ON2
(Note 8)
V
OUT
= 5.5V, AINSEL and CLK/SEL
ON1,
ON2,
AINSEL and CLK/SEL
CLK/SEL = OUT
260
80
200
200
100
300
85
0.8V
OUT
0.8V
OUT
1
340
90
400
0.2V
OUT
0.2V
OUT
V
V
µA
kHz
%
kHz
ns
ns
3
Rising V
OUT
, V
POKIN
< 0.1V
Rising V
POKIN
I
SINK
= 1mA, V
OUT
= 3.6V or
I
SINK
= 20µA, V
OUT
= 1V
V
OUT
= V
POK
= 5.5V
V
POKIN
= 1.5V
0.01
2.95
1.225
3.10
1.275
0.4
1
50
V
V
V
µA
nA
I
SINK
= 1mA
I
SOURCE
= 1mA
AINSEL = GND
AINSEL = OUT
f
CLK
= 400kHz, V
AIN1
= V
AIN2
= 2.5V
f
CLK
= 400kHz, 5ms conversion,
monotonic to 8 bits
V
OUT
- 0.4
0.625
0
1
1.875
2.5
2
±4
0.4
V
V
V
V
µA
% FSR
CLK/SEL = GND
CLK/SEL = OUT
CLK/SEL = OUT
MAX848
MAX849
MAX848
MAX849
600
1100
120
250
0.1
0.1
0.3
0.13
0.25
800
1350
200
400
20
20
0.6
0.25
0.5
1000
1600
300
550
mA
Ω
µA
µA
CONDITIONS
Current into OUT pin, CLK/SEL = GND
Current into OUT pin, CLK/SEL = OUT,
does not include switching losses
MIN
TYP
35
150
MAX
90
300
UNITS
µA
µA
MAX848/MAX849
_______________________________________________________________________________________
1-Cell to 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters
MAX848/MAX849
ELECTRICAL CHARACTERISTICS
(V
OUT
= 3.6V, GND = PGND = CLK/SEL = ON1 =
ON2
= AINSEL = AIN1 = AIN2 = FB = POKIN, POUT = OUT,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 9)
PARAMETER
REFERENCE
Reference Output Voltage
DC-DC CONVERTER
Output Voltage (Note 3)
FB Regulation Voltage
Output Voltage Lockout Range
OUT Supply Current in Shutdown
OUT Supply Current in Low-Power
Mode (Note 6)
OUT Supply Current in Low-Noise
Mode (Note 6)
DC-DC SWITCHES
Switch On-Resistance
N-channel
P-channel
CLK/SEL = OUT
N-Channel Current Limit
CLK/SEL = GND (Note 7)
ADC
Accuracy
POWER-GOOD
Internal Trip Level
External Trip Level
LOGIC CONTROL INPUTS
Internal Oscillator Frequency
Oscillator Maximum Duty Cycle
CLK/SEL = OUT
260
80
340
90
kHz
%
Rising V
OUT
, V
POKIN
< 0.1V
Rising V
POKIN
2.95
1.225
3.10
1.275
V
V
f
CLK
= 400kHz, 5ms conversion
±4
% FSR
CLK/SEL = GND
CLK/SEL = OUT
CLK/SEL = OUT
MAX848
MAX849
MAX848
MAX849
600
1100
120
250
0.6
0.25
0.5
1100
1800
300
550
mA
Ω
V
FB
< 0.1V, CLK/SEL = OUT,
includes load-regulation error
Adjustable output, CLK/SEL = OUT
(Note 3)
V
ON2
= 3.6V
CLK/SEL = GND
CLK/SEL = OUT, does not include
switching losses
3.13
1.21
2.05
3.47
1.27
2.45
20
90
300
V
V
V
µA
µA
µA
I
REF
= 0mA
1.225
1.275
V
CONDITIONS
MIN
TYP
MAX
UNITS
Note 1:
Minimum operating voltage. Because the MAX848/MAX849 are bootstrapped to the output, it will operate down to a 0.7V input.
Note 2:
In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than in low-noise mode (CLK/SEL = OUT or
synchronized).
Note 3:
The part is in start-up mode until it reaches this voltage level. Do not apply full-load current.
Note 4:
Load regulation is measured from no load to full load, where full load is determined by the N-channel switch current limit.
Note 5:
Start-up is tested with Figure 2’s circuit. Output current is measured when the input and output voltages are applied.
Note 6:
Supply current from the 3.34V output is measured between the 3.34V output and the OUT pin. This current correlates directly
with actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. V
OUT
= 3.6V to keep
the internal switch open when measuring the current into the device.
Note 7:
When V
CLK/SEL
= 0V, the inductor is forced into constant-peak-current, discontinuous operation. This is guaranteed by
testing in Figure 2’s circuit.
Note 8:
ON1 and
ON2
inputs have approximately 0.15V
OUT
hysteresis.
Note 9:
Specifications to -40°C are guaranteed by design, not production tested.
4
_______________________________________________________________________________________
1-Cell to 3-Cell, High-Power,
Low-Noise, Step-Up DC-DC Converters
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
MAX849
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V)
MAX848/9 TOC-01
MAX848/MAX849
MAX849
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5V)
MAX848/9 TOC-02
MAX848
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 3.3V)
MAX848/9 TOC-03
100
90
EFFICIENCY (%)
80
70
60
50
40
0.1
1
10
100
V
IN
= 0.9V
V
IN
= 2.4V
V
IN
= 1.2V
100
V
IN
= 3.6V
90
80
70
60
50
V
IN
= 1.2V
V
IN
= 2.4V
100
V
IN
= 2.4V
90
EFFICIENCY (%)
EFFICIENCY (%)
80
V
IN
= 1.2V
70
PFM
PWM
60
0.1
1
10
100
1000
0.1
V
IN
= 0.9V
PFM
PWM
1
10
100
1000
PFM
PWM
1000
40
30
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LOAD CURRENT (mA)
NO-LOAD BATTERY CURRENT
vs. INPUT VOLTAGE
MAX848/9 TOC-04
SHUTDOWN CURRENT
vs. INPUT VOLTAGE
MAX848/9 TOC-05
START-UP VOLTAGE vs. LOAD CURRENT
(V
OUT
= 3.3V, PWM MODE)
1.8
START-UP VOLTAGE (V)
1.6
1.4
1.2
1.0
0.8
T
A
= +85°C
T
A
= +25°C
6
MAX848/9 TOC-06
14
12
INPUT CURRENT (mA)
10
8
T
A
= +25°C
6
4
2
0
0
1
2
3
4
5
T
A
= -40°C
T
A
= +85°C
18
16
SHUTDOWN CURRENT (µA)
14
12
10
8
6
4
2
0
T
A
= -40°C
0
1
2
3
4
5
INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
CAPACITOR LEAKAGE
DOMINATES AT
T
A
= +85°C
T
A
= +85°C
T
A
= +25°C
2.0
T
A
= -40°C
6
0.6
0.01
0.1
1
10
100
1000
LOAD CURRENT (mA)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
REFERENCE VOLTAGE
vs. TEMPERATURE
MAX848/9 TOC-07
REFERENCE VOLTAGE
vs. REFERENCE CURRENT
MAX848/9 TOC-08
ADC LINEARITY ERROR
vs. FULL-SCALE INPUT VOLTAGE
MAX848/9 TOC-09
1.252
1.252
1.250
REFERENCE VOLTAGE (V)
1.248
1.246
1.244
1.242
1.240
0.25
0.15
LINEARITY ERROR (%FS)
REFERENCE VOLTAGE (V)
1.251
0.05
AIN2
1.250
-0.05
AIN1
-0.15
1.249
1.248
-40
-20
0
20
40
60
80
100
TEMPERATURE (°C)
1.238
0
10
20
30
40
50
60
70
80
REFERENCE CURRENT (µA)
-0.25
0.1875
0.4375
0.6875
0.9375
FULL-SCALE INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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