MAX849 MAXIM [Maxim Integrated Products], MAX849 Datasheet

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MAX849

Manufacturer Part Number
MAX849
Description
1-Cell to 3-Cell, High-Power, Low-Noise, Step-Up DC-DC Converters
Manufacturer
MAXIM [Maxim Integrated Products]
Datasheet

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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.
Pin Configuration appears at end of data sheet.
Dual Mode is a trademark of Maxim Integrated Products.
19-1095; Rev 2; 12/97
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.
V
(V)
0.9
1.2
2.4
2.7
3.6
IN
Typical Output Selector Guide
V
(V)
3.3
3.3
3.3
3.3
OUT
5
5
5
5
5
________________________________________________________________ Maxim Integrated Products
MAX849 I
Low-Noise, Step-Up DC-DC Converters
General Description
(mA)
1000
100
300
200
750
500
800
600
70
OUT
MAX848 I
(mA)
110
200
130
250
150
300
70
40
70
1-Cell to 3-Cell, High-Power,
OUT
A/D CHANNEL SELECT
Digital Cordless Phones
Cellular Phones
Palmtop Computers
Local 3.3V to 5V Supplies
Up to 95% Efficiency
(see Typical Output Selector Guide below)
3.3V Dual Mode™ or 2.7V to 5.5V Adj. Output
0.7V to 5.5V Input Range
0.15mW Standby Mode
300kHz PWM Mode or Synchronizable
Two-Channel ADC with Serial Output
Power-Good Function
A/D CHANNEL 1 IN
A/D CHANNEL 2 IN
ON/OFF CONTROL
INPUT
0.8V TO 5.5V
MAX848ESE
MAX849ESE
SYNC INPUT
PART
A/D OUTPUT
Typical Operating Circuit
AIN1
AIN2
AINSEL
DATA
ON1
ON2
CLK/SEL
POKIN
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
REF
Ordering Information
MAX848
MAX849
GND
PCS Phones
Hand-Held Instruments
Personal Communicators
PGND
POUT
OUT
POK
LX
FB
Applications
PIN-PACKAGE
16 Narrow SO
16 Narrow SO
Features
VOLTAGE MONITOR
OUTPUT
OUTPUT
1

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MAX849 Summary of contents

Page 1

... Rev 2; 12/97 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 ...

Page 2

... Output Voltage Lockout Range Load Regulation (Note 4) Minimum Start-Up Voltage (Note 5) Frequency in Start-Up Mode Operating Current in Shutdown 2 _______________________________________________________________________________________ Operating Temperature Range MAX848ESE/MAX849ESE .................................-40°C to +85°C Junction Temperature ......................................................+150°C + 0.3V) POUT Storage Temperature.........................................-65°C to +160°C Lead Temperature (soldering, 10sec) .............................+300°C + 0.3V) OUT ...

Page 3

... OUT 5.5V ON2 LX OUT CLK/SEL = GND N-channel CLK/SEL = OUT P-channel CLK/SEL = OUT MAX848 CLK/SEL = OUT MAX849 MAX848 (Note 7) CLK/SEL MAX849 I = 1mA SINK I = 1mA SOURCE AINSEL = GND AINSEL = OUT f = 400kHz 2.5V CLK AIN1 AIN2 f = 400kHz, 5ms conversion, CLK monotonic to 8 bits ...

Page 4

... LOGIC CONTROL INPUTS Internal Oscillator Frequency Oscillator Maximum Duty Cycle 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). ...

Page 5

... INPUT VOLTAGE (V) REFERENCE VOLTAGE vs. TEMPERATURE 1.252 1.251 1.250 1.249 1.248 -40 - TEMPERATURE (°C) _______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power, Typical Operating Characteristics MAX849 EFFICIENCY vs. LOAD CURRENT (V = 5V) OUT 100 PFM 40 PWM 30 1000 0.1 1 ...

Page 6

High-Power, Low-Noise, Step-Up DC-DC Converters (T = +25°C, unless otherwise noted.) A HEAVY-LOAD SWITCHING WAVEFORMS (V = 3.3V) OUT MAX848/9 TOC- s/div V = 1.1V 200mA 3.3V IN OUT ...

Page 7

... OUT 60 80 100 MAX849 DECT LOAD-TRANSIENT RESPONSE MAX848/9 TOC- 2ms/div V = 1.2V 3.3V 440 F IN OUT OUT RIPPLE, 200mV/div, AC COUPLED OUT B = LOAD CURRENT, 50mA TO 400mA, 0.2A/div, PULSE WIDTH = 416 100k 1M MAX849 PEAK INDUCTOR CURRENT vs. OUTPUT VOLTAGE 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.2 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT VOLTAGE (V) 3.3V 0A 5.5 7 ...

Page 8

High-Power, Low-Noise, Step-Up DC-DC Converters PIN NAME 1 AIN1 ADC’s Channel 1 Input. Analog input voltage range is 0.625V to 1.875V. 2 AIN2 ADC’s Channel 2 Input. Analog input voltage range 2.5V. 3 REF ...

Page 9

... ADC standard application circuit for the MAX849 configured in the high-power PWM mode. The MAX848/MAX849 are turned on or off by logic input pins ON1 and ON2 (Table 1). When ON1 = 1 or ON2 = 0, the part is on. When ON1 = 0 and ON2 = 1, the part is off. Both inputs have logic trip points near ...

Page 10

... The N-channel power MOSFET turns on until either the output voltage is in regulation or the inductor current limit is reached (0.8A for the MAX848 and 1.4A for the MAX849). The switch turns off for the remainder of the cycle and the inductor energy is delivered to the output 10 ______________________________________________________________________________________ ...

Page 11

... Setting the Output Voltage Externally section. Analog-to-Digital Converter (ADC) The MAX848/MAX849 have an internal, two-channel, seri- al ADC. The ADC converts an analog input voltage into a digital stream available at the DATA pin. The converter skips clock pulses in proportion to the input voltage. ...

Page 12

... MAX848 and 1.4A for the MAX849. However generally acceptable to bias the inductor into saturation by approximately 20% (the point where the inductance is 20% below the nominal value). ...

Page 13

... The controller reads the switch status and pulls ON1 low. The switch is released and ON2 is pulled high. Power Amplifier (PA) and Radio Supply The MAX849 is an ideal power supply for the power amplifier (PA) and the radio used in digital cordless and PCS phones (Figure 10). The PA is directly pow- ered by the MAX849 for maximum output swing ...

Page 14

... This resistor should be large enough to mini- mize the shutdown current The MAX848/MAX849 turn on when ON1 = 1 or ON2 = 0. The µC monitors the battery voltage and turns off the device (forces ON1 low and ON2 high) when the bat- RESET tery is weak. ...

Page 15

... Low-Noise, Step-Up DC-DC Converters Pin Configuration TOP VIEW 1 16 AIN1 2 15 AIN2 3 14 REF MAX848 4 13 GND MAX849 5 OUT 12 11 POKIN POK 8 Narrow SO ______________________________________________________________________________________ 1-Cell to 3-Cell, High-Power, ON1 ON2 POUT LX PGND CLK/SEL DATA AINSEL Package Information 15 ...

Page 16

High-Power, Low-Noise, Step-Up DC-DC Converters Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry ...

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