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PDF MAX1705 Data sheet ( Hoja de datos )
| Número de pieza | MAX1705 | |
| Descripción | 1- to 3-Cell / High-Current / Low-Noise / Step-Up DC-DC Converters with Linear Regulator | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-1198; Rev 0; 4/97
EVALUAATVIOANILKAIBTLMEANUAL 1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
_______________General Description
The MAX1705/MAX1706 are high-efficiency, low-noise,
step-up DC-DC converters with an auxiliary linear-
regulator output. These devices are intended for use in
battery-powered wireless applications. They use a syn-
chronous rectifier pulse-width-modulation (PWM) boost
topology to generate 2.5V to 5.5V outputs from battery
inputs, such as 1 to 3 NiCd/NiMH cells or 1 Li-Ion cell.
The MAX1705 has an internal 1A N-channel MOSFET
switch. The MAX1706 has a 0.5A switch. Both devices
also have a built-in low-dropout linear regulator that
delivers up to 200mA.
With an internal synchronous rectifier, the MAX1705/
MAX1706 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 1µA shutdown mode. An
efficiency-enhancing track mode reduces the step-up
DC-DC converter output to 300mV above the linear-reg-
ulator output.
Both devices come in a 16-pin QSOP package, which
occupies the same space as an 8-pin SO. Other features
include two shutdown-control inputs for push-on/push-off
control, and an uncommitted comparator for use as a volt-
age monitor.
________________________Applications
Digital Cordless Phones
Personal Communicators
Palmtop Computers
Hand-Held Instruments
PCS Phones
Wireless Handsets
Two-Way Pagers
__________________Pin Configuration
TOP VIEW
LBP 1
LBN 2
REF 3
TRACK 4
GND 5
OUT 6
FB 7
FBLDO 8
MAX1705
MAX1706
QSOP
16 POUT
15 ONA
14 ONB
13 LX
12 PGND
11 CLK/SEL
10 LBO
9 LDO
____________________________Features
o Up to 96% Efficiency
o 1.1VIN Guaranteed Start-Up
o Up to 850mA Output (MAX1705)
o Step-Up Output (2.5V to 5.5V adjustable)
o Linear Regulator (1.25V to 5.0V adjustable)
o PWM/PFM Synchronous-Rectified Topology
o 300kHz PWM Mode or Synchronizable
o 1µA Shutdown Mode
o Voltage Monitor
o Pushbutton On/Off Control
______________Ordering Information
PART
TEMP. RANGE
PIN-PACKAGE
MAX1705C/D
0°C to +70°C
Dice*
MAX1705EEE
-40°C to +85°C
16 QSOP
MAX1706C/D
0°C to +70°C
Dice*
MAX1706EEE
-40°C to +85°C
16 QSOP
*Dice are tested at TA = +25°C, DC parameters only.
__________Typical Operating Circuit
INPUT 0.7V TO 5.5V
LOW-BATTERY
DETECTION
ON/OFF CONTROL
HIGH
EFFICIENCY
LOW
NOISE
LX
LBP
POUT
OUT
MAX1705 FB
LBO MAX1706
ONA
ONB
CLK/SEL
TRACK
LBN
LDO
FBLDO
REF GND PGND
STEP-UP OUTPUT
LINEAR
REGULATOR
OUTPUT
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800
1 page  
1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
ELECTRICAL CHARACTERISTICS (continued)
(VOUT = VPOUT = VLBP = 3.6V, CLK/SEL = FB = LBN = LBO = ONA = ONB = TRACK = GND, REF = open (bypassed with 0.22µF),
LX = open, TA = -40°C to +85°C, unless otherwise noted, Note 4.)
PARAMETER
SYMBOL
LINEAR REGULATOR
FBLDO Regulation Voltage
FBLDO Input Current
Short-Circuit Current Limit
Dropout Resistance
LOW-BATTERY COMPARATOR
LBN, LBP Offset
LBN, LBP Common-Mode
Input Range
LBO High Leakage
CONTROL INPUTS
Input Low Level
Input High Level
Internal Oscillator Frequency
External Oscillator
Synchronization Range
CONDITIONS
FBLDO = LDO, ILOAD = 1mA
VFBLDO = 1.5V
FBLDO = LDO = GND
VFBLDO = 1V, ILDO = 200mA
LBP falling
LBN = 0.5V and 1.5V (at least one input must
be within this range)
LBO = OUT = 5V
1.2V < VOUT < 5.5V, ONA, ONB (Note 2)
VOUT = 2.5V, CLK/SEL, TRACK
1.2V < VOUT < 5.5V, ONA, ONB (Note 2)
VOUT = 5.5V, CLK/SEL, TRACK
CLK/SEL = OUT
MIN TYP MAX
1.233
1.268
0.01 50
220 600
1.2
-5 5
0.5 1.5
1
0.85VOUT
0.85VOUT
260
200
0.15VOUT
0.15VOUT
340
400
UNITS
V
nA
mA
Ω
mV
V
µA
V
V
kHz
kHz
Note 1: Once the output is in regulation, the MAX1705/MAX1706 operate down to a 0.7V input voltage.
Note 2: The device is in start-up mode when VOUT is below this value (see Low-Voltage Start-Up Oscillator section).
Note 3: ONA and ONB inputs have a hysteresis of approximately 0.15VOUT.
Note 4: Specifications to -40°C to are guaranteed by design, not production tested.
_______________________________________________________________________________________ 5
5 Page 
1- to 3-Cell, High-Current, Low-Noise,
Step-Up DC-DC Converters with Linear Regulator
INPUT 0.9V TO 3.6V
C7
22µF
(TO PGND)
R6
R5
C8
0.33µF
L1 10µH (22µH)
LX
POUT
LBP OUT
LBN TRACK
REF
PGND
MAX1705
MAX1706
FB
ONA
ONB
CLK/SEL
LBO
LDO
FBLDO
GND
D1
BOOST OUTPUT 3.6V
C9
0.33µF
C3 R1
0.1µF 191k
R2
100k
C4
C1* 220µF
(100µF)
(TO PGND)
LDO OUTPUT 3.3V
R3
165k
C2*
C5*
0.33µF
C6
22µF
NOTE: HEAVY LINES INDICATE HIGH-CURRENT PATH.
R7
100k
R4
100k
*OPTIONAL.
( ) ARE FOR MAX1706.
Figure 2. Typical Operating Circuit (PWM Mode)
Step-Up Converter
The step-up switching DC-DC converter generates an
adjustable output to supply both power circuitry (such
as RF power amplifiers) and the internal low-dropout
linear regulator. During the first part of each cycle, the
internal N-channel MOSFET switch is turned on. This
allows current to ramp up in the inductor and store
energy in a magnetic field. During the second part of
each cycle, when the MOSFET is turned off, the voltage
across the inductor reverses and forces current
through the diode and synchronous rectifier to the out-
put filter capacitor and load. As the energy stored in
the inductor is depleted, the current ramps down, and
the output diode and synchronous rectifier turn off.
Voltage across the load is regulated using either PWM
or PFM operation, depending on the CLK/SEL pin set-
ting (Table 1).
Low-Noise, High-Power PWM Operation
When CLK/SEL is pulled high, the MAX1705/MAX1706
operate in a high-power, low-noise PWM mode. During
PWM operation, they switch at a constant frequency
(300kHz), and modulate the MOSFET switch pulse
width to control the power transferred per cycle and
regulate the voltage across the load. In PWM mode, the
Table 1. Selecting the Operating Mode
CLK/SEL
0
MODE
PFM
1 PWM
External Clock
Synchronized
(200kHz to 400kHz)
PWM
FEATURES
Low supply current
Low noise,
high output current
Low noise,
high output current
devices can output up to 850mA. Switching harmonics
generated by fixed-frequency operation are consistent
and easily filtered.
During PWM operation, each of the internal clock’s ris-
ing edges sets a flip-flop, which turns on the N-channel
MOSFET switch (Figure 3). The switch is turned off
when the sum of the voltage-error and current-
feedback signals trips a multi-input comparator and
resets the flip-flop; the switch remains off for the rest of
the cycle. When a change occurs in the output voltage
error signal into the comparator, it shifts the level that
the inductor current is allowed to ramp to during each
cycle and modulates the MOSFET switch pulse width.
A second comparator enforces a 1.55A (max) inductor-
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet MAX1705.PDF ] | |
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