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PDF MAX1700 Data sheet ( Hoja de datos )
| Número de pieza | MAX1700 | |
| Descripción | Step-Up DC-DC Converters | |
| Fabricantes | Maxim Integrated | |
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19-4759; Rev 1; 1/99
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
General Description
The MAX1700/MAX1701 are high-efficiency, low-noise,
step-up DC-DC converters intended for use in battery-
powered wireless applications. They use a synchro-
nous-rectified pulse-width-modulation (PWM) boost
topology to generate 2.5V to 5.5V outputs from battery
inputs such as one to three NiCd/NiMH cells or one Li-
Ion cell. Both devices have an internal 1A, 130mΩ N-
channel MOSFET switch and a 250mΩ P-channel
synchronous rectifier.
With their internal synchronous rectifier, the MAX1700/
MAX1701 deliver 5% better efficiency than similar non-
synchronous converters. They also feature a pulse-
frequency-modulation (PFM) standby mode to improve
efficiency at light loads, and a 3µA shutdown mode.
The MAX1700/MAX1701 come in 16-pin QSOP pack-
ages (which occupy the same space as an 8-pin SO).
The MAX1701 includes two comparators to generate
power-good and low-battery warning outputs. It also
contains a gain block that can be used to build a linear
regulator using an external P-channel pass device.
For higher-power outputs, refer to the MAX1703. For
dual outputs (step-up and linear regulator), refer to the
MAX1705/MAX1706. For an on-board analog-to-digital
converter, refer to the MAX848/MAX849.
The MAX1701 evaluation kit is available to speed design
time.
Applications
Digital Cordless Phones Personal Communicators
PCS Phones
Palmtop Computers
Wireless Handsets
Hand-Held Instruments
Two-Way Pagers
Pin Configurations
TOP VIEW
I.C. 1
I.C. 2
REF 3
CLK/SEL 4
GND 5
I.C. 6
ONB 7
ONA 8
MAX1700
16 I.C.
15 POUT
14 OUT
13 LX
12 PGND
11 FB
10 I.C.
9 I.C.
QSOP
I.C. = INTERNAL CONNECTION. LEAVE OPEN OR CONNECT TO GND
Pin Configurations continued at end of data sheet.
Features
o Up to 96% Efficiency
o 1.1 VIN Guaranteed Start-Up
o 0.7V to 5.5V Input Range
o Up to 800mA Output
o Step-Up Output (adjustable from 2.5V to 5.5V)
o PWM/PFM Synchronous-Rectified Topology
o External Clock or Internal 300kHz Oscillator
o 3µA Logic-Controlled Shutdown
o Power-Good Output (MAX1701)
o Low-Battery Comparator (MAX1701)
o Uncommitted Gain Block (MAX1701)
PART
MAX1700EEE
MAX1701EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
Typical Operating Circuit
INPUT
0.7V TO 5.5V
ON
OFF
OFF
ON
PWM OR
PFM SYNC
MAX1700
ONA LX
ONB
CLK/SEL POUT
OUTPUT
3.3V OR ADJ
UP TO 800mA
REF OUT
FB GND PGND
________________________________________________________________ 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 (1A),
Low-Noise, Step-Up DC-DC Converters
ELECTRICAL CHARACTERISTICS (continued)
(CLK/SEL = ONA = ONB = FB = PGND = GND, OUT = POUT, VOUT = 3.6V, MAX1701: AIN = LBN = GND, LBP = REF,
TA = -40°C to +85°C, unless otherwise noted.) (Note 8)
PARAMETER
CONDITIONS
MIN TYP MAX UNITS
LOGIC AND CONTROL INPUTS
Input Low Voltage (Note 7)
Input High Voltage (Note 7)
Input High Voltage (Note 7)
Logic Input Current
1.2V < VOUT < 5.5V, ONA and ONB
2.5V < VOUT < 5.5V, CLK/SEL
1.2V < VOUT < 5.5V, ONA and ONB
2.5V < VOUT < 5.5V, CLK/SEL
ONA, ONB, and CLK/SEL
0.8VOUT
0.8VOUT
-1
0.2VOUT
0.2VOUT
1
V
V
µA
Internal Oscillator Frequency CLK/SEL = OUT
260 340 kHz
Oscillator Maximum Duty Cycle
80 92 %
External Clock Frequency
Range
200 400 kHz
Note 1: Operating voltage. Since the regulator is bootstrapped to the output, once started it will operate down to 0.7V input.
Note 2: Start-up is tested with the circuit of Figure 2.
Note 3: In low-power mode (CLK/SEL = GND), the output voltage regulates 1% higher than low-noise mode (CLK/SEL = OUT or
synchronized).
Note 4: The regulator is in start-up mode until this voltage is reached. Do not apply full load current.
Note 5: Load regulation is measured from no-load to full load where full load is determined by the N-channel switch current limit.
Note 6: Supply current from the 3.30V output is measured between the 3.30V output and the OUT pin. This current correlates
directly to the actual battery supply current, but is reduced in value according to the step-up ratio and efficiency. Set VOUT
= 3.6V to keep the internal switch open when measuring the current into the device.
Note 7: ONA and ONB have hysteresis of approximately 0.15xVOUT.
Note 8: Specifications to -40°C are guaranteed by design and not production tested.
(TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
EFFICIENCY vs. LOAD CURRENT
(VOUT = 3.3V)
100
VIN = 2.4V
90
80
70 VIN = 1.2V
60 VIN = 0.9V
50
40
0.1
PFM
PWM
1 10 100
LOAD CURRENT (mA)
1000
EFFICIENCY vs. LOAD CURRENT
(VOUT = 5V)
100
VIN = 3.6V
90
80 VIN = 2.4V
70
60 VIN = 1.2V
50
40
30
0.1
PFM
PWM
1 10 100
LOAD CURRENT (mA)
1000
7.0
6.0
5.0
4.0
3.0
2.0
1.0
0
0
MAX1701
SHUTDOWN CURRENT
vs. INPUT VOLTAGE (V)
T = 25°C
T = 85°C
T = -40°C
12345
INPUT VOLTAGE (V)
6
_______________________________________________________________________________________ 5
5 Page 
1-Cell to 3-Cell, High-Power (1A),
Low-Noise, Step-Up DC-DC Converters
ERROR
COMPARATOR
FB
REF
400mA
CURRENT
LIMIT
QD
Q
R
LOGIC HIGH
SQ
R
POUT
P
LX
N
PGND
Figure 4. Controller Block Diagram in Low-Power PFM Mode
Synchronized PWM Operation
By applying an external clock to CLK/SEL, the
MAX1700/MAX1701 can also be synchronized in PWM
mode to a frequency between 200kHz and 400kHz.
This allows the user to set the harmonics to avoid IF
bands in wireless applications. The synchronous rectifi-
er is also active during synchronized PWM operation.
Low-Power PFM Operation
Pulling CLK/SEL low places the MAX1700/MAX1701 in
a low-power mode. During low-power mode, PFM oper-
ation regulates the output voltage by transferring a
fixed amount of energy during each cycle and then
modulating the switching frequency to control the
power delivered to the output. The devices switch only
as needed to service the load, resulting in the highest
possible efficiency at light loads. Output current capa-
bility in PFM mode is 100mA. The output voltage is typi-
cally 1% higher than the output voltage in PWM mode.
During PFM operation, the error comparator detects the
output voltage falling out of regulation and sets a flip-
flop, turning on the N-channel MOSFET switch (Figure
4). When the inductor current ramps to the PFM mode
current limit (400mA typical) and stores a fixed amount
of energy, the current-sense comparator resets a flip-
flop. The flip-flop turns off the N-channel switch and
turns on the P-channel synchronous rectifier. A second
flip-flop, previously reset by the switch’s “on” signal,
inhibits the error comparator from initiating another
cycle until the energy stored in the inductor is trans-
ferred to the output filter capacitor and the synchronous
rectifier current has ramped down to 70mA. This forces
operation with a discontinuous inductor current.
Synchronous Rectifier
The MAX1700/MAX1701 feature an internal 250mΩ, P-
channel synchronous rectifier to enhance efficiency.
Synchronous rectification provides a 5% efficiency
improvement over similar nonsynchronous boost regu-
lators. In PWM mode, the synchronous rectifier is
turned on during the second half of each switching
cycle. In low-power mode, an internal comparator turns
on the synchronous rectifier when the voltage at LX
exceeds the boost-regulator output and then turns it off
when the inductor current drops below 70mA.
Low-Voltage Start-Up Oscillator
The MAX1700/MAX1701 use a CMOS, low-voltage
start-up oscillator for a 1.1V guaranteed minimum start-
up input voltage at +25°C. On start-up, the low-voltage
oscillator switches the N-channel MOSFET until the out-
put voltage reaches 2.15V. Above this level, the normal
boost-converter feedback and control circuitry take
over. Once the device is in regulation, it can operate
down to a 0.7V input since internal power for the IC is
bootstrapped from the output using the OUT pin. Do
not apply full load until the output exceeds 2.4V.
Table 3. On/Off Logic Control
ONA
ONB
00
01
10
11
Status
On
Off
On
On
Shutdown
The MAX1700/MAX1701 shut down to reduce quies-
cent current to typically 3µA. During shutdown, the ref-
erence, low-battery comparator, gain block, and all
feedback and control circuitry are off. The boost con-
verter’s output drops to one Schottky diode drop below
the input.
Table 3 shows the control logic with ONA and ONB.
Both inputs have trip points near 0.5VOUT with
0.15VOUT hysteresis.
Low-Battery Comparator (MAX1701)
The internal low-battery comparator has uncommitted
inputs and an open-drain output (LBO) capable of sink-
ing 1mA. To use it as a low-battery-detection compara-
tor, connect the LBN input to the reference, and
connect the LBP input to an external resistor divider
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX1700.PDF ] | |
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