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PDF MAX1703 Data sheet ( Hoja de datos )
| Número de pieza | MAX1703 | |
| Descripción | 1-Cell to 3-Cell / High-Power 1.5A / Low-Noise / Step-Up DC-DC Converter | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1336; Rev 2; 11/98
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
1-Cell to 3-Cell, High-Power (1.5A),
Low-Noise, Step-Up DC-DC Converter
________________General Description
The MAX1703 is a high-efficiency, low-noise, step-up
DC-DC converter intended for use in battery-powered
wireless applications. It uses a synchronous-rectified
pulse-width-modulation (PWM) boost topology to gen-
erate a 2.5V to 5.5V output from battery inputs, such as
one to three NiCd/NiMH cells or one Li-Ion cell. The
device includes a 2A, 75mΩ, N-channel MOSFET
switch and a 140mΩ, P-channel synchronous rectifier.
With its internal synchronous rectifier, the MAX1703
delivers up to 5% better efficiency than similar nonsyn-
chronous converters. It also features a pulse-frequency-
modulation (PFM) low-power mode to improve efficiency
at light loads, and a 1µA shutdown mode.
The MAX1703 comes in a 16-pin narrow SO package
and includes an uncommitted comparator that generates
a power-good or low-battery-warning output. It also
contains a linear gain block that can be used to build a
linear regulator.
For lower-power outputs and a smaller package, refer
to the MAX1700/MAX1701. For dual outputs (step-up
plus linear regulator), refer to the MAX1705/MAX1706.
For an on-board analog-to-digital converter, refer to the
MAX848/MAX849.
The MAX1703 evaluation kit is available to speed designs.
____________________________Features
o Up to 95% Efficiency
o Up to 1.5A Output
o Fixed 5V or Adjustable Step-Up Output
(2.5V to 5.5V)
o 0.7V to 5.5V Input Range
o Low-Power Mode (300µW)
o Low-Noise, Constant-Frequency Mode (300kHz)
o Synchronizable Switching Frequency
(200kHz to 400kHz)
o 1µA Logic-Controlled Shutdown
o Power-Good Comparator
o Uncommitted Gain Block
PART
MAX1703ESE
Ordering Information
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
16 Narrow SO
________________________Applications
Digital Cordless Phones Personal Communicators
PCS Phones
Palmtop Computers
Wireless Handsets
Two-Way Pagers
Hand-Held Instruments
Typical Operating Circuit
Pin Configuration
INPUT
0.7V TO 5.5V
OFF
ON
PWM
OR
SYNC
PFM
POWER-GOOD
INPUT
GAIN-BLOCK INPUT
MAX1703
LXP, LXN
ON POUT
CLK/
SEL
OUT
POKIN
AIN POK
REF AO
FB GND PGND
OUTPUT
5V OR ADJ
UP TO 1.5A
POWER-GOOD
OUTPUT
GAIN-BLOCK
OUTPUT
TOP VIEW
REF 1
FB 2
POKIN 3
OUT 4
GND 5
AIN 6
AO 7
POK 8
MAX1703
16 ON
15 POUT
14 LXP
13 POUT
12 PGND
11 LXN
10 PGND
9 CLK/SEL
Narrow SO
________________________________________________________________ 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 1-800-835-8769.
1 page  
1-Cell to 3-Cell, High-Power (1.5A),
Low-Noise, Step-Up DC-DC Converter
__________________________________________Typical Operating Characteristics
(VIN = +3.6V, VOUT = 5V, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(VOUT = 5V)
100
VIN = 3.6V
90
80 VIN = 2.4V
70 VIN = 1.2V
60
50
40
0.1
PFM
PWM
1 10 100 1000 10,000
LOAD CURRENT (mA)
SHUTDOWN SUPPLY CURRENT
vs. INPUT VOLTAGE
2.5
INCLUDES ALL EXTERNAL
COMPONENT LEAKAGES.
2.0 CAPACITOR LEAKAGE
DOMINATES AT TA = +85°C
1.5 TA = +85°C
EFFICIENCY vs. LOAD CURRENT
(VOUT = 3.3V)
100
VIN = 2.4V
90
80 VIN = 1.2V
70 VIN = 0.9V
60
50
40
0.1
PFM
PWM
1 10 100 1000 10,000
LOAD CURRENT (mA)
START-UP VOLTAGE vs. LOAD CURRENT
2.0
VOUT = 5V
1.8 PWM MODE
1.6
1.4
NO-LOAD BATTERY CURRENT
vs. INPUT VOLTAGE
4
LOW-POWER MODE
3
2 TA = +85°C
1 TA = +25°C
0 TA = -40°C
01
2 34
INPUT VOLTAGE (V)
5
1.2550
REFERENCE VOLTAGE
vs. TEMPERATURE
6
1.2530
1.2510
1.0 1.2
1.0
0.5
TA = +25°C,
TA = -40°C
0.8
1.2490
1.2470
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
0.6
0.01
0.1 1
10 100
LOAD CURRENT (mA)
1000
1.2450
-40 -20 0 20 40 60 80 100
TEMPERATURE (°C)
1.2520
1.2510
1.2500
REFERENCE VOLTAGE
vs. REFERENCE CURRENT
VIN = 3.6V
VOUT = 5V
LOW-POWER MODE
1.2490
1.2480
1.2470
1.2460
0 10 20 30 40 50 60 70 80 90
REFERENCE CURRENT (µA)
NOISE SPECTRUM
9
8 VOUT = 5V
VIN = 3.6V
7 ILOAD = 500mA
6
5
4
3
2
1
0
-1
100
1k 10k 100k 1M
FREQUENCY (Hz)
10M
_______________________________________________________________________________________ 5
5 Page 
1-Cell to 3-Cell, High-Power (1.5A),
Low-Noise, Step-Up DC-DC Converter
Shutdown
The MAX1703 shuts down to reduce quiescent current
to 1µA. During shutdown (ON = VOUT), the reference,
low-battery comparator, gain block, and all feedback
and control circuitry are off. The boost converter’s out-
put drops to one Schottky diode drop below the input.
Power-Good (POK) Comparator
The MAX1703 features an uncommitted POK compara-
tor. The internal POK comparator has an open-drain
output (POK) capable of sinking 1mA. When the input
(POKIN) rises above the 1.25V reference, the POK
open-drain output turns off. The POKIN input has 10mV
of hysteresis.
To provide a power-good signal, connect the POKIN
input to an external resistor-divider between OUT and
GND (Figure 5). Calculate the resistor values as follows:
R3 = R4(VTH / VREF - 1)
where VTH is the desired input voltage trip threshold.
Since the input bias current into POKIN is less than
20nA, R4 can be a large value (such as 270kΩ or less)
without sacrificing accuracy. Connect the resistor volt-
age-divider as close to the IC as possible, within 0.2in.
(5mm) of POKIN.
Reference
The MAX1703 has an internal 1.250V, 1% bandgap ref-
erence. Connect a 0.22µF bypass capacitor to GND
within 0.2in. (5mm) of the REF pin. REF can source up
to 50µA of external load current.
Gain Block
The MAX1703 gain block can function as a second
comparator, or can be used to build a linear regulator
using an external P-channel MOSFET pass device. The
gain-block output is a single-stage transconductance
amplifier that drives an open-drain N-channel MOSFET.
The gm of the entire gain-block stage is 10mmho.
Figure 6 shows the gain block used in a linear-regulator
application. The output of an external P-channel pass
element is compared to the internal reference. The dif-
ference is amplified and used to drive the gate of the
pass element. Use a logic-level PFET, such as an
NDS336P (RDS(ON) = 270mΩ) from Fairchild. This con-
figuration allows ripple reduction at the output. If a
lower RDS(ON) PFET is used, then the linear regulator
output filter capacitance may need to be increased.
To use the gain block as a comparator, refer to the
Power-Good (POK) Comparator section.
VIN
R3
R4
C3
0.22µF
L1
4.7µH
C1
100µF
CLK/SEL
LXP, LXN
POUT
MAX1703
ON
OUT
AIN
MBR0520L
D1
R5
10Ω
C5
0.22µF
C2
0.22µF
OUTPUT
C4
2 x 220µF
POKIN
REF
PGND
AO
POK
FB
GND
R1
R2
SIGNAL GROUND
NOTE: HEAVY LINES INDICATE HIGH-CURRENT PATHS.
Figure 5. Adjustable Output (PWM Mode)
POWER GROUND
VIN
L1
4.7µH
CLK/SEL
LXP, LXN
C1
100µF
MBR0520L
BOOST
OUTPUT
LINEAR
REGULATED
P OUTPUT
C4
POUT
330µF R6
20k
R5
ON MAX1703
10Ω C5
R3 OUT 0.22µF
C2
AIN 0.22µF
47µF
POKIN
AO
POK
R4 R1
REF FB
PGND GND
R2
100k
SIGNAL GROUND
POWER GROUND
Figure 6. Using the Gain Block as a Linear Regulator
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX1703.PDF ] | |
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