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PDF MAX668-MAX669 Data sheet ( Hoja de datos )
| Número de pieza | MAX668-MAX669 | |
| Descripción | 1.8V to 28V Input / PWM Step-Up Controllers in MAX | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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19-4778; Rev 0a; 8/98
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
General Description
The MAX668/MAX669 constant-frequency, pulse-width-
modulating (PWM), current-mode DC-DC controllers are
designed for a wide range of DC-DC conversion applica-
tions including step-up, SEPIC, flyback, and isolated-
output configurations. Power levels of 20W or more can
be controlled with conversion efficiencies of over 90%.
The 1.8V to 28V input voltage range supports a wide
range of battery and AC-powered inputs. An advanced
BiCMOS design features low operating current (220µA),
adjustable operating frequency (100kHz to 500kHz),
soft-start, and a SYNC input allowing the MAX668/
MAX669 oscillator to be locked to an external clock.
DC-DC conversion efficiency is optimized with a low
100mV current-sense voltage as well as with Maxim’s
proprietary Idle Mode™ control scheme. The controller
operates in PWM mode at medium and heavy loads for
lowest noise and optimum efficiency, then pulses only as
needed (with reduced inductor current) to reduce oper-
ating current and maximize efficiency under light loads.
A logic-level shutdown input is also included, reducing
supply current to 3.5µA.
The MAX669, optimized for low input voltages with a
guaranteed start-up voltage of 1.8V, requires boot-
strapped operation (IC powered from boosted output). It
supports output voltages up to 28V. The MAX668 oper-
ates with inputs as low as 3V and can be connected in
either a bootstrapped or non-bootstrapped (IC powered
from input supply or other source) configuration. When
not bootstrapped, it has no restriction on output voltage.
Both ICs are available in an extremely compact 10-pin
µMAX package.
Typical Operating Circuit
Features
o 1.8V Minimum Start-Up Voltage (MAX669)
o Wide Input Voltage Range (1.8V to 28V)
o Tiny 10-Pin µMAX Package
o Current-Mode PWM and Idle Mode™ Operation
o Efficiency over 90%
o Adjustable 100kHz to 500kHz Oscillator or
SYNC Input
o 220µA Quiescent Current
o Logic-Level Shutdown
o Soft-Start
Applications
Cellular Telephones
Telecom Hardware
LANs and Network Systems
POS Systems
PART
MAX668EUB
MAX669EUB
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
10 µMAX
Idle Mode is a trademark of Maxim Integrated Products.
Pin Configuration
VIN = 1.8V to 28V
SYNC/ VCC
SHDN
FREQ
EXT
CS+
MAX669
LDO PGND
REF
GND
FB
VOUT = 28V
TOP VIEW
LDO 1
FREQ 2
GND 3
REF 4
FB 5
MAX668
MAX669
µMAX
10 SYNC/SHDN
9 VCC
8 EXT
7 PGND
6 CS+
________________________________________________________________ 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  
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
Typical Operating Characteristics
(Circuits of Figures 2, 3, 4, and 5; TA = +25°C; unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(VOUT = 5V)
95
90 VIN = 3.6V
VIN = 3.3V
85
80 VIN = 2.7V
75 VIN = 2V
70
65
60
55
50
1
BOOTSTRAPPED
FIGURE 3
R4 = 200kΩ
10 100 1000
LOAD CURRENT (mA)
10,000
MAX669 MINIMUM START-UP VOLTAGE
vs. LOAD CURRENT
3.0
VOUT = 5V
2.5
2.0
VOUT = 12V
1.5
1.0
0.5
0
0
BOOTSTRAPPED
FIGURE 2
100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
SHUTDOWN CURRENT vs.
SUPPLY VOLTAGE
3.5
MAX669
3.0
2.5 MAX668
2.0
1.5
1.0
0.5
0
0
CURRENT INTO VCC PIN
5 10 15 20 25
SUPPLY VOLTAGE (V)
30
MAX668 EFFICIENCY vs.
LOAD CURRENT (VOUT = 12V)
95
90
85
80
75
70
1
VIN = 5V
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ
10 100 1000
LOAD CURRENT (mA)
10,000
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
1200
CURRENT INTO VCC PIN
1000 ROSC = 500kΩ
800
600 MAX669
400
200
0
0
MAX668
5 10 15 20 25
SUPPLY VOLTAGE (V)
30
SUPPLY CURRENT vs.
TEMPERATURE
290
270
ROSC = 100kΩ
250
230
ROSC = 200kΩ
210
ROSC = 500kΩ
190
170
150
-40 -20
0 20 40 60
TEMPERATURE (°C)
80 100
MAX668 EFFICIENCY vs.
LOAD CURRENT (VOUT = 24V)
95
VIN = 12V
90
VIN = 8V
85
VIN = 5V
80
75
70
1
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ
10 100 1000
LOAD CURRENT (mA)
10,000
NO-LOAD SUPPLY CURRENT vs.
SUPPLY VOLTAGE
4000
3500
VOUT = 12V
BOOTSTRAPPED
3000
FIGURE 2
R4 = 200kΩ
2500
2000
1500
1000
500
0
0 2 4 6 8 10 12
SUPPLY VOLTAGE (V)
LDO DROPOUT VOLTAGE vs.
LDO CURRENT
300
250
VIN = 3V
200
150
VIN = 4.5V
100
50
0
0.1
1
LDO CURRENT (mA)
10 20
_______________________________________________________________________________________ 5
5 Page 
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
VIN = 3V to 12V
C4
1µF
C2
0.1µF
C3
0.22µF
1 LDO
9 VCC
10 SYNC/
SHDN
4 REF
2
FREQ
R4
100k
1%
MAX668
C1
68µF L1
20V 4.7µH
EXT 8
CS+
PGND
6
R1
0.02Ω
7
5
FB
3
GND
N1 D1
MBRS340T3
FDS6680
C5
68µF
20V
C7
220pF
C6
68µF
20V R2
218k
1%
R3
24.9k
1%
Figure 4. MAX668 High-Voltage Non-Bootstrapped Configuration
VOUT = 12V @ 1A
C8
0.1µF
VIN = 2.7V to 5.5V
1 LDO
C2
1µF
9 VCC
C3
0.22µF
10 SYNC/
SHDN
4 REF
2
FREQ
R4
100k
1%
MAX668
C1
68µF L1
10V 4.7µH
EXT 8
CS+
PGND
6
R1
0.02Ω
7
5
FB
3
GND
N1 D1
MBRS340T3
FDS6680
C4
68µF
20V
C7
220pF
C5
68µF
20V
R2
218k
1%
R3
24.9k
1%
VOUT = 12V @ 1A
C6
0.1µF
Figure 5. MAX668 Low-Voltage Non-Bootstrapped Configuration
Non-Bootstrapped Operation
With non-bootstrapped operation, the IC is powered
from the input voltage (VIN) or another source, such as
a logic supply. Non-bootstrapped operation (Figure 4)
is recommended (but not required) for input voltages
above 5V, since the EXT amplitude (limited to 5V by
LDO) at this voltage range is no higher than it would be
with bootstrapped operation. Note that non-boot-
strapped operation is required if the output voltage
exceeds 28V, since this level is too high to safely con-
nect to VCC. Also note that only the MAX668 can be
used with non-bootstrapped operation.
If the input voltage does not exceed 5.5V, the on-chip
regulator can be disabled by connecting VCC to LDO
(Figure 5). This eliminates the regulator forward drop
and supplies the maximum gate drive to the external
FET for lowest on-resistance. Disabling the regulator
also reduces the non-bootstrapped minimum input volt-
age from 3V to 2.7V.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 18 Páginas | |
| PDF Descargar | [ Datasheet MAX668-MAX669.PDF ] | |
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