MAX668/MAX669
General Description
1.8V to 28V Input, PWM Step-Up
Controllers in μMAX
Benefits and Features
●
1.8V Minimum Start-Up Voltage (MAX669)
●
Wide Input Voltage Range (1.8V to 28V)
● Tiny 10-Pin μMAX Package
●
Current-Mode PWM and Idle Mode™ Operation
●
Efficiency over 90%
● Adjustable 100kHz to 500kHz Oscillator or
SYNC Input
● 220μA Quiescent Current
●
Logic-Level Shutdown
●
Soft-Start
The MAX668/MAX669 constant-frequency, pulse-width-
modulating (PWM), current-mode DC-DC controllers are
designed for a wide range of DC-DC conversion applications
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 operating
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 bootstrapped
operation (IC powered from boosted output). It supports
output voltages up to 28V. The MAX668 operates with
inputs as low as 3V and can be connected in either a boot-
strapped or non-bootstrapped (IC powered from input sup-
ply or other source) configuration. When not bootstrapped,
it has no restriction on output voltage. Both ICs are avail-
able in an extremely compact 10-pin μMAX package.
Applications
●
●
●
●
Cellular Telephones
Telecom Hardware
LANs and Network Systems
POS Systems
Ordering Information
PART
MAX668EUB
MAX669EUB
MAX669EUB/V+T
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
10 µMAX
10 µMAX
Idle Mode is a trademark of Maxim Integrated Products.
+ Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
/V Denotes an automotive qualified part.
Note:
Devices are also available in a lead(Pb)-free/RoHS-
compliant package. Specify lead-free by adding “+” to the part
number when ordering.
Typical Operating Circuit
V
IN
= 1.8V to 28V
Pin Configuration
TOP VIEW
SYNC/
SHDN
FREQ
V
CC
V
OUT
= 28V
EXT
CS+
LDO 1
FREQ
GND
REF
FB
2
3
4
5
10 SYNC/SHDN
MAX669
LDO
PGND
FB
GND
MAX668
MAX669
9
8
7
6
V
CC
EXT
PGND
CS+
REF
µMAX
19-4778; Rev 3; 6/16
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in μMAX
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
Soldering Temperature (Reflow)......................................+300°C
Lead(Pb)-Free Packages ................................................+260°C
Packages Containing Lead(Pb).......................................+240°C
Electrical Characteristics
(V
CC
= V
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
Input Voltage Range, V
CC
Input Voltage Range with V
CC
Tied to LDO
FB Threshold
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)
4.50
2.65
2.40
1.225
1.0
225
425
85
2.50
1.250
-2
1.1
250
500
100
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 Load Regulation
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
)
0.012
1
100
15
0.2
220
3.5
5.00
20
115
25
1
350
6
5.50
%/%
nA
mV
mV
µA
µA
µA
REFERENCE AND LDO REGULATORS
LDO Output Voltage
LDO load =
∞ to 400Ω
V
5.50
2.60
1.275
-10
1.2
275
575
115
kHz
V
V
mV
V
Undervoltage Lockout Threshold
REF Output Voltage
REF Load Regulation
REF Undervoltage Lockout Threshold
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%
Oscillator Frequency
R
OSC
= 100kΩ ±1%
R
OSC
= 500kΩ ±1%
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Maxim Integrated
│
2
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in μMAX
Electrical Characteristics (continued)
(V
CC
= V
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)
V
SYNC/SHDN
= 5V
V
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
Electrical Characteristics
(V
CC
= V
LDO
= +5V, R
OSC
= 200kΩ, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
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
)
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)
4.50
2.65
2.40
V
FB
= 1.30V
MAX668
MAX669
3
1.8
2.7
1.22
85
3
28
28
5.5
1.28
20
115
27
1
350
6
5.50
V
5.50
2.60
V
V
V
V
nA
mV
mV
µA
µA
µA
CONDITIONS
MIN
MAX
UNITS
REFERENCE AND LDO REGULATORS
LDO Output Voltage
LDO load =
∞ to 400Ω
LDO Undervoltage Lockout Threshold
Sensed at LDO, falling edge,
hysteresis = 1%, MAX669 only
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Maxim Integrated
│
3
MAX668/MAX669
1.8V to 28V Input, PWM Step-Up
Controllers in μMAX
Electrical Characteristics (continued)
(V
CC
= V
LDO
= +5V, R
OSC
= 200kΩ, T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
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)
V
SYNC/SHDN
= 5V
V
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.
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Maxim Integrated
│
4
MAX668/MAX669
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.)
MAX668 toc01
MAX668 toc02
90
85
EFFICIENCY (%)
80
75
70
65
60
55
50
1
V
IN
= 3.6V
V
IN
= 3.3V
V
IN
= 2.7V
V
IN
= 2V
90
EFFICIENCY (%)
85
80
75
70
V
IN
= 5V
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ
1
10
100
1000
90
EFFICIENCY (%)
85
80
75
70
V
IN
= 12V
V
IN
= 8V
V
IN
= 5V
BOOTSTRAPPED
FIGURE 3
R4 = 200kΩ
10
100
1000
10,000
LOAD CURRENT (mA)
NON-BOOTSTRAPPED
FIGURE 4
R4 = 200kΩ
1
10
100
1000
LOAD CURRENT (mA)
10,000
10,000
LOAD CURRENT (mA)
MAX669 MINIMUM START-UP VOLTAGE
vs. LOAD CURRENT
MAX668 toc04
SUPPLY CURRENT vs.
SUPPLY VOLTAGE
MAX668 toc05
NO-LOAD SUPPLY CURRENT vs.
SUPPLY VOLTAGE
NO-LOAD SUPPLY CURRENT (µA)
3500
3000
2500
2000
1500
1000
500
0
0
2
4
6
8
10
12
V
OUT
= 12V
BOOTSTRAPPED
FIGURE 2
R4 = 200kΩ
MAX668 toc06
3.0
MINIMUM START-UP VOLTAGE (V)
2.5
2.0
1.5
1.0
0.5
0
BOOTSTRAPPED
FIGURE 2
0
V
OUT
= 12V
V
OUT
= 5V
1200
1000
SUPPLY CURRENT (µA)
800
600
400
200
0
MAX668
0
5
10
15
20
25
MAX669
CURRENT INTO V
CC
PIN
R
OSC
= 500kΩ
4000
100 200 300 400 500 600 700 800 900 1000
LOAD CURRENT (mA)
30
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
SHUTDOWN CURRENT vs.
SUPPLY VOLTAGE
3.0
2.5
2.0
1.5
1.0
0.5
0
0
5
10
CURRENT INTO V
CC
PIN
15
20
25
30
MAX669
MAX668
MAX668 toc07
SUPPLY CURRENT vs.
TEMPERATURE
MAX668 toc08
LDO DROPOUT VOLTAGE vs.
LDO CURRENT
MAX668 toc09
3.5
290
270
SUPPLY CURRENT (µA)
250
230
210
190
170
150
-40
-20
0
20
40
60
80
R
OSC
= 100kΩ
300
LDO DROPOUT VOLTAGE (mV)
250
200
150
100
50
0
V
IN
= 3V
SHUTDOWN CURRENT (µA)
R
OSC
= 200kΩ
R
OSC
= 500kΩ
V
IN
= 4.5V
100
0.1
1
LDO CURRENT (mA)
10
20
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
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Maxim Integrated
│
5
MAX668 toc03
95
EFFICIENCY vs. LOAD CURRENT
(V
OUT
= 5V)
95
MAX668 EFFICIENCY vs.
LOAD CURRENT (V
OUT
= 12V)
95
MAX668 EFFICIENCY vs.
LOAD CURRENT (V
OUT
= 24V)
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