19-4778; Rev 0a; 8/98
ANUAL
N KIT M EET
ATIO
EVALU
TA SH
WS DA
FOLLO
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
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
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.
MAX668/MAX669
Applications
Cellular Telephones
Telecom Hardware
LANs and Network Systems
POS Systems
Ordering Information
PART
MAX668EUB
MAX669EUB
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.
Typical Operating Circuit
V
IN
= 1.8V to 28V
Pin Configuration
TOP VIEW
V
OUT
= 28V
SYNC/
SHDN
FREQ
V
CC
EXT
CS+
LDO
1
FREQ
GND
2
3
4
5
10
SYNC/SHDN
9
V
CC
EXT
PGND
CS+
MAX668
MAX669
8
7
6
MAX669
LDO
PGND
FB
REF
GND
REF
FB
µMAX
________________________________________________________________
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.
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
MAX668/MAX669
ABSOLUTE MAXIMUM RATINGS
V
CC
to GND ..........................................................-0.3V to +30V
PGND to GND....................................................................±0.3V
SYNC/SHDN
to GND .............................................-0.3V to +30V
EXT, REF to GND.....................................-0.3V to (V
LDO
+ 0.3V)
LDO, FREQ, FB, CS+ to GND ................................ -0.3V to +6V
LDO Output Current...........................................-1mA to +20mA
REF Output Current..............................................-1mA to +1mA
LDO Short Circuit to GND .........................................Momentary
REF Short Circuit to GND ..........................................Continuous
Continuous Power Dissipation (T
A
= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ..........444mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering,10sec) ..............................+300°C
ELECTRICAL CHARACTERISTICS
(V
CC
= LDO = +5V, R
OSC
= 200kΩ, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
PWM Controller
PWM CONTROLLER
Input Voltage Range, V
CC
Input Voltage Range with V
CC
Tied to LDO
FB Threshold
FB Threshold Load Regulation
Typically 0.013% per mV on CS+;
V
CS
+ range is 0 to 100mV for 0 to full
load current.
Typically 0.012% per % duty factor on
EXT; EXT duty factor for a step-up is:
100% (1 – V
IN
/V
OUT
)
V
FB
= 1.30V
85
5
CS+ forced to GND
V
FB
= 1.30V, V
CC
= 3V to 28V
SYNC/SHDN = GND, V
CC
= 28V
5V
≤
V
CC
≤
28V
(includes LDO dropout)
3V
≤
V
CC
≤
28V
(includes LDO dropout)
MAX668
MAX669
3
1.8
2.7
1.225
1.250
0.013
28
28
5.5
1.275
V
V
V
%/mV
CONDITIONS
MIN
TYP
MAX
UNITS
FB Threshold Line Regulation
FB Input Current
Current Limit Threshold
Idle Mode Current-Sense Threshold
CS+ Input Current
V
CC
Supply Current (Note 1)
Shutdown Supply Current (V
CC
)
REFERENCE AND LDO REGULATORS
Reference and LDO Regulators
0.012
1
100
15
0.2
220
3.5
20
115
25
1
350
6
%/%
nA
mV
mV
µA
µA
µA
4.50
2.65
2.40
1.225
1.0
225
425
85
5.00
5.50
V
5.50
LDO Output Voltage
LDO load =
∞
to 400Ω
Undervoltage Lockout Threshold
REF Output Voltage
REF Load Regulation
REF Undervoltage Lockout Threshold
OSCILLATOR
Oscillator
Sensed at LDO, falling edge,
hysteresis = 1%, MAX668 only
No load, C
REF
= 0.22µF
REF load = 0 to 50µA
Rising edge, 1% hysteresis
R
OSC
= 200kΩ ±1%
2.50
1.250
-2
1.1
250
500
100
2.60
1.275
-10
1.2
275
575
115
V
V
mV
V
Oscillator Frequency
R
OSC
= 100kΩ ±1%
R
OSC
= 500kΩ ±1%
kHz
2
_______________________________________________________________________________________
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= LDO = +5V, R
OSC
= 200kΩ, T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
Maximum Duty Cycle
Minimum EXT Pulse Width
Minimum SYNC Input-Pulse Duty Cycle
Minimum SYNC Input Low Pulse Width
SYNC Input Rise/Fall Time
SYNC Input Frequency Range
SYNC/SHDN Falling Edge to Shutdown Delay
SYNC/SHDN Input High Voltage
SYNC/SHDN Input Low Voltage
SYNC/SHDN Input Current
EXT Sink/Source Current
EXT On-Resistance
3.0V < V
CC
< 28V
1.8V < V
CC
< 3.0V (MAX669)
3.0V < V
CC
< 28V
1.8V < V
CC
< 3.0V (MAX669)
SYNC/SHDN = 5V
SYNC/SHDN = 28V
EXT forced to 2V
EXT high or low
0.5
1.5
1
2
5
2.0
1.5
0.45
0.30
3.0
6.5
Not tested
100
70
CONDITIONS
R
OSC
= 200kΩ ±1%
R
OSC
= 100kΩ ±1%
R
OSC
= 500kΩ ±1%
MIN
87
86
86
TYP
90
90
90
290
20
50
45
200
200
500
MAX
93
94
94
ns
%
ns
ns
kHz
µs
V
V
µA
A
Ω
%
UNITS
MAX668/MAX669
ELECTRICAL CHARACTERISTICS
(V
CC
= LDO = +5V, R
OSC
= 200kΩ, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
PWM Controller
PWM CONTROLLER
Input Voltage Range, V
CC
Input Voltage Range with V
CC
Tied to LDO
FB Threshold
FB Input Current
Current-Limit Threshold
Idle Mode Current-Sense Threshold
CS+ Input Current
V
CC
Supply Current (Note 1)
Shutdown Supply Current (V
CC
)
Reference and LDO Regulators
REFERENCE AND LDO REGULATORS
LDO load =
∞
to 400Ω
5V
≤
V
CC
≤
28V
(includes LDO dropout)
3V
≤
V
CC
≤
28V
(includes LDO dropout)
4.50
2.65
2.40
5.50
V
5.50
2.60
V
V
CS+ forced to GND
V
FB
= 1.30V, V
CC
= 3V to 28V
SYNC/SHDN = GND, V
CC
= 28V
V
FB
= 1.30V
85
3
MAX668
MAX669
3
1.8
2.7
1.22
28
28
5.5
1.28
20
115
27
1
350
6
V
V
V
nA
mV
mV
µA
µA
µA
CONDITIONS
MIN
MAX
UNITS
LDO Output Voltage
LDO Undervoltage Lockout Threshold
Sensed at LDO, falling edge,
hysteresis = 1%, MAX669 only
_______________________________________________________________________________________
3
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
MAX668/MAX669
ELECTRICAL CHARACTERISTICS (continued)
(V
CC
= LDO = +5V, R
OSC
= 200kΩ, T
A
= -40°C to +85°C, unless otherwise noted.)
PARAMETER
REF Output Voltage
REF Load Regulation
REF Undervoltage Lockout Threshold
OSCILLATOR
R
OSC
= 200kΩ ±1%
Oscillator Frequency
R
OSC
=100kΩ ±1%
R
OSC
= 500kΩ ±1%
R
OSC
= 200kΩ ±1%
Maximum Duty Cycle
Minimum SYNC Input-Pulse Duty Cycle
Minimum SYNC Input Low Pulse Width
SYNC Input Rise/Fall Time
SYNC Input Frequency Range
SYNC/SHDN Input High Voltage
SYNC/SHDN Input Low Voltage
SYNC/SHDN Input Current
EXT On-Resistance
3.0V < V
CC
< 28V
1.8V < V
CC
< 3.0V (MAX669)
3.0V < V
CC
< 28V
1.8V < V
CC
< 3.0V (MAX669)
SYNC/SHDN = 5V
SYNC/SHDN = 28V
EXT high or low
Not tested
100
2.0
1.5
0.45
0.30
3.0
6.5
5
R
OSC
= 100kΩ ±1%
R
OSC
= 500kΩ ±1%
222
425
85
87
86
86
278
575
115
93
94
94
45
200
200
500
%
ns
ns
kHz
V
V
µA
Ω
%
kHz
CONDITIONS
No load, C
REF
= 0.22µF
REF load = 0 to 50µA
Rising edge, 1% hysteresis
1.0
MIN
1.22
MAX
1.28
-10
1.2
UNITS
V
mV
V
Note 1:
This is the V
CC
current consumed when active but not switching. Does not include gate-drive current.
Note 2:
Limits at T
A
= -40°C are guaranteed by design.
4
_______________________________________________________________________________________
1.8V to 28V Input, PWM Step-Up
Controllers in µMAX
Typical Operating Characteristics
(Circuits of Figures 2, 3, 4, and 5; T
A
= +25°C; unless otherwise noted.)
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5V)
90
85
EFFICIENCY (%)
EFFICIENCY (%)
80
75
70
65
60
55
50
1
10
100
1000
10,000
LOAD CURRENT (mA)
BOOTSTRAPPED
FIGURE 3
R4 = 200kΩ
75
V
IN
= 2.7V
V
IN
= 2V
V
IN
= 3.6V
V
IN
= 3.3V
MAX668 toc01
MAX668/MAX669
MAX668 EFFICIENCY vs.
LOAD CURRENT (V
OUT
= 12V)
MAX668 toc02
MAX668 EFFICIENCY vs.
LOAD CURRENT (V
OUT
= 24V)
V
IN
= 12V
90
EFFICIENCY (%)
V
IN
= 8V
MAX668 toc03
95
95
95
90
85
85
V
IN
= 5V
80
V
IN
= 5V
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ
1
10
100
1000
10,000
80
75
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ
1
10
100
1000
LOAD CURRENT (mA)
10,000
70
LOAD CURRENT (mA)
70
MAX669 MINIMUM START-UP VOLTAGE
vs. LOAD CURRENT
MAX668 toc04
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX668 toc05
NO-LOAD SUPPLY CURRENT vs.
SUPPLY VOLTAGE
3500
3000
2500
2000
1500
1000
500
0
V
OUT
= 12V
BOOTSTRAPPED
FIGURE 2
R4 = 200kΩ
MAX668 toc06
3.0
MINIMUM START-UP VOLTAGE (V)
2.5
2.0
V
OUT
= 12V
1.5
1.0
0.5
0
0
V
OUT
= 5V
1200
1000
SUPPLY CURRENT (µA)
800
600
400
200
MAX668
0
0
5
10
15
20
25
MAX669
CURRENT INTO V
CC
PIN
R
OSC
= 500kΩ
4000
NO-LOAD SUPPLY CURRENT (µA)
BOOTSTRAPPED
FIGURE 2
100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
30
0
2
4
6
8
10
12
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT vs.
SUPPLY VOLTAGE
MAX669
MAX668 toc07
SUPPLY CURRENT vs.
TEMPERATURE
MAX668 toc08
LDO DROPOUT VOLTAGE vs.
LDO CURRENT
MAX668 toc09
3.5
3.0
SHUTDOWN CURRENT (µA)
2.5
2.0
1.5
1.0
0.5
CURRENT INTO V
CC
PIN
0
0
5
10
15
20
25
290
270
SUPPLY CURRENT (µA)
250
230
R
OSC
= 200kΩ
210
R
OSC
= 500kΩ
190
170
150
R
OSC
= 100kΩ
300
250
V
IN
= 3V
200
150
V
IN
= 4.5V
100
50
0
MAX668
30
-40
-20
0
20
40
60
80
100
LDO DROPOUT VOLTAGE (mV)
0.1
1
LDO CURRENT (mA)
10
20
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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