MAX1709ESE Maxim Integrated Products, MAX1709ESE Datasheet - Page 9

• Manufacturer Part Number: MAX1709ESE
• Description: IC DC/DC CONV STEP-UP 4A 16-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1709ESE

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 3.3V, 5V, Adj
• Current - Output: 4A
• Frequency - Switching: 600kHz
• Voltage - Input: 0.7 ~ 5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-SOIC (3.9mm Width)
• Power - Output: 1.3W
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: Q1226679

Table 1. On/Off Logic Control
Figure 2. Simplified Functional Diagram
The MAX1709 switches at a constant frequency
(600kHz) and modulates the MOSFET switch pulse
width to control the power transferred per cycle and
regulate the voltage across the load. In low-noise appli-
cations, the fundamental and the harmonics generated
by the fixed switching frequency are easily filtered out.
Figure 2 shows the simplified functional diagram for the
MAX1709. Figure 3 shows the simplified PWM con-
troller functional diagram. The MAX1709 enters syn-
chronized current-mode PWM when a clock signal
(350kHz < f
wireless or noise-sensitive applications, this ensures
that switching harmonics are predictable and kept out-
side the IF frequency band(s). High-frequency opera-
tion permits low-magnitude output ripple voltage and
minimum inductor and filter capacitor size. Switching
losses will increase at the higher frequencies (see
Power Dissipation ).
The MAX1709 features Dual-Mode™ operation. When
FB is connected to ground, the MAX1709 generates a
fixed output voltage of either +3.3V or +5V, depending
Dual Mode is a trademark of Maxim Integrated Products, Inc.
ONA
0
0
1
1
CLK
3.3/5
GND
OUT
ONA
ONB
CLK
REF
FB
< 1000kHz) is applied to CLK. For
_______________________________________________________________________________________
_______________________________________________________________________________________
Setting the Output Voltage
IC POWER
2.15V
ONB
0
1
0
1
1.260V
ON
REFERENCE
DUAL MODE
UNDERVOLTAGE LOCKOUT
FB
4A, Low-Noise, High-Frequency,
RDY
MAX1709
Operation
On
Off
On
On
OUT
Step-Up DC-DC Converter
EN
EN
OSCILLATOR
OSCILLATOR
on the logic applied to the 3.3/5 input (Figure 1). The
output can be configured for other voltages, using two
external resistors as shown in Figure 4. To set the out-
put voltage externally, choose an R3 value that is large
enough to minimize load at the output but small enough
to minimize errors due to leakage and the time constant
to FB. A value of R3
where V
The soft-start pin allows the soft-start time to be adjust-
ed by connecting a capacitor from SS/LIM to ground.
Select capacitor C3 (connected to SS/LIM pin) as:
where t
current limit to reach full value.
To improve efficiency or reduce inductor size at
reduced load currents, the current limit can be reduced
Table 2. Selecting Switching Frequency
MAX1709
STARTUP
600kHz
(350kHz−1000kHz)
External clock
SS
FB
Q
Soft-Start/Current-Limit Adjustment
= 1.24V.
is the time (in seconds) it takes the switch
CLK
0
1
D
EN
OSC
FB
CONTROLLER
FIGURE 3.
C3 (in µF) = 3.2
PWM
R
SEE
4
≤
=
50kΩ is required.
R
3
⎛
⎜ ⎜
⎝
V
V
O U T
FB
N
Synchronized PWM

−
1
t
⎞
⎟ ⎟
⎠
SS
Not allowed
LX
PGND
MODE
PWM
(SS/LIM)
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