MAX1677EEE+ Maxim Integrated Products, MAX1677EEE+ Datasheet - Page 10

• Manufacturer Part Number: MAX1677EEE+
• Description: IC DC-DC CONV DL HI EFF 16QSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1677EEE+

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 3.3V or Adj Main, -28 ~ 28 V or Adj Secondary
• Current - Output: 350mA
• Frequency - Switching: 300kHz
• Voltage - Input: 0.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Power - Output: 696mW
• Output Voltage: 2.5 V to 5.5 V
• Output Current: 350 mA
• Input Voltage: 0.7 V to 5.5 V
• Supply Current: 35 uA
• Switching Frequency: 300 KHz
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Compact, High-Efficiency, Dual-Output
Step-Up and LCD Bias DC-DC Converter
Figure 2. LCD Converter in Positive Mode
Figure 3. LCD Converter in Negative Mode
10
0.1µF
0.1µF
C4
______________________________________________________________________________________
C4
GND
OUT
LCDON
CLK/SEL
ON
LCDPOL
PGND
GND
OUT
LCDON
CLK/SEL
ON
LCDPOL
PGND
MAX1677
MAX1677
10Ω
R3
10Ω
R3
LCDGND
LCDLX
LCDFB
LCDGND
POUT
LCDLX
LCDFB
REF
POUT
LX
FB
REF
LX
FB
10µH
C5
0.1µF
10µH
L1
L2
10µH
C5
0.1µF
10µH
R2
R1
L1
L2
R2
C6
0.1µF
R1
MBR0530
3.3V MAIN
BOOST OUTPUT
3.3V MAIN
BOOST OUTPUT
C2
100µF
D2
MBR0530
D3
C3
4.7µF
C2
100µF
LCD BOOST OUTPUT
C1
100µF
D2
MBR0530
C3
4.7µF
V
IN
-LCD BOOST
OUTPUT
C1
100µF
V
IN
output voltage. In PWM mode, the MBC can supply up
to 350mA. Switching harmonics generated by the fixed-
frequency operation are consistent and easily filtered.
During PWM operation, the rising edge of the internal
clock sets a flip-flop, which turns on the N-channel
MOSFET (Figure 4). The switch turns off when the sum
of the voltage-error, slope-compensation, and current-
feedback signals trips the multi-input comparator and
resets the flip-flop; the switch remains off for the rest of
the cycle. Changes in the output voltage error signal
shift the inductor current level and modulate the MOS-
FET pulse width.
The MAX1677 operates as a clock-synchronized cur-
rent-mode PWM when a clock signal (200kHz to
400kHz) is applied to CLK/SEL. This allows switching
harmonics to be positioned to avoid sensitive frequen-
cy bands, such as those near IF frequencies in wireless
applications.
Pulling CLK/SEL low places the MAX1677 in low-power
standby mode. During standby mode, PFM operation
regulates the output voltage by transferring a fixed
amount of energy during each cycle, and then modulat-
ing the switching frequency to control the power deliv-
ered to the output. The device switches only as needed
to service the load, resulting in the highest possible effi-
ciency at light loads and an operating current of only
20µA. The MBC can supply up to 170mA when in PFM
mode (Table 1).
Figure 4. Controller Block Diagram in PWM Mode
PWM-MODE
LIMIT LEVEL
FEEDBACK
CURRENT-
REF
OSC
Clock-Synchronized PWM
S
R
Q
Low Power PFM Mode
P
POUT
N
PGND
LX