MAX1771CSA Maxim Integrated Products, MAX1771CSA Datasheet - Page 8

• Manufacturer Part Number: MAX1771CSA
• Description: IC DC/DC CTRLR STEP-UP HE 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1771CSA

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 12V, 2 ~ 16.5 V
• Current - Output: 2A
• Frequency - Switching: 300kHz
• Voltage - Input: 2 ~ 16.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Power - Output: 471mW
• Output Voltage: 12 V
• Output Current: 2 A
• Input Voltage: 2 V to 16.5 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Case: SOP8
• Dc: 02+
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

12V or Adjustable, High-Efficiency,
Low I
Figure 2a. 12V Preset Output, Bootstrapped
Figure 2c. 9V Output, Bootstrapped
increases at low input voltages. However, the supply
current is also reduced because V+ is at a lower volt-
age, and because less energy is consumed while
charging and discharging the external MOSFET’s gate
capacitance. The minimum input voltage is 3V when
using external feedback resistors. With supply voltages
below 5V, bootstrapped mode is recommended.
Note: When using the MAX1771 in non-boot-
strapped mode, there is no preset output operation
because V+ is also the output voltage sense point
8
0.1µF
0.1µF
R2 = (R1)
V
REF
C3
C3
_______________________________________________________________________________________
= 1.5V
5
4
6
(
5
4
3
6
C2
0.1µF
C2
0.1µF
V
V
OUT
REF
REF
SHDN
AGND
REF
SHDN
FB
AGND
-1
Q
)
MAX1771
MAX1771
GND
GND
, Step-Up DC-DC Controller
V+
V+
2
2
7
7
EXT
EXT
CS
CS
FB
1
8
3
1
8
22µH
22µH
V
V
L1
L1
IN
IN
28kΩ
= 4V
= 5V
N
Si9410DY/
MTD20N03HDL
Si9410DY/
MTD20N03HDL
1N5817-22
N
R
40mΩ
R1
1N5817-22
R
40mΩ
SENSE
SENSE
D1
D1
47µF
68µF
C1
C1
140kΩ
100pF
C5
R2
C4
200µF
C4
300µF
V
OUT
V
AT 0.5A
OUT
= 12V
= 9V
for fixed-output operation. External resistors must
be used to set the output voltage. Use 1% external
feedback resistors when operating in adjustable-output
mode (Figures 2b, 2c) to achieve an overall output volt-
age accuracy of ±5%. To achieve highest efficiency,
operate in bootstrapped mode whenever possible.
The MAX1771 uses a proprietary current-limited PFM
control scheme to provide high efficiency over a wide
range of load currents. This control scheme combines the
ultra-low supply current of PFM converters (or pulse skip-
pers) with the high full-load efficiency of PWM converters.
Unlike traditional PFM converters, the MAX1771 uses a
sense resistor to control the peak inductor current. The
device also operates with high switching frequencies
(up to 300kHz), allowing the use of miniature external
components.
As with traditional PFM converters, the power transistor
is not turned on until the voltage comparator senses
the output is out of regulation. However, unlike tradition-
al PFM converters, the MAX1771 switch uses the com-
bination of a peak current limit and a pair of one-shots
that set the maximum on-time (16µs) and minimum off-
time (2.3µs); there is no oscillator. Once off, the mini-
mum off-time one-shot holds the switch off for 2.3µs.
After this minimum time, the switch either 1) stays off if
the output is in regulation, or 2) turns on again if the
output is out of regulation.
Figure 2b. 12V Output, Non-Bootstrapped
0.1µF
V
68µF
R2 = (R1)
V
REF
IN
C3
C1
= 5V
= 1.5V
(
5
4
6
V
V
OUT
REF
REF
SHDN
AGND
-1
C2
0.1µF
)
MAX1771
GND
V+
2
7
External Power-Transistor
EXT
CS
FB
1
8
3
22µH
L1
18kΩ
MTD20N03HDL
N
PFM Control Scheme
1N5817-22
R
40mΩ
R1
Control Circuitry
SENSE
D1
300µF
C4
127kΩ
100pF
R2
C5
V
OUT
AT 0.5A
= 12V