MAX1972EEE+ Maxim Integrated Products, MAX1972EEE+ Datasheet - Page 14

• Manufacturer Part Number: MAX1972EEE+
• Description: IC REG STP DWN 750MA 16-QSOP
• Manufacturer: Maxim Integrated Products
• Type: Step-Down (Buck)r

Specifications of MAX1972EEE+

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 2
• Voltage - Output: 1.5V, 1.8V, 2.5V, 3.3V, Adj
• Current - Output: 750mA
• Frequency - Switching: 1.4MHz
• Voltage - Input: 2.6 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-QSOP
• Power - Output: 667mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Both output voltages can be selected in three different
ways as indicated by Table 1. Each output has two pre-
set voltages that can be set using FBSEL_ and it can
also be set to any voltage from 0.8V to V
external resistor voltage-divider.
To use a resistor-divider to set the output voltage to
1.2V or higher (Figure 5), connect a resistor from FB_ to
OUT_ (R_
(R_
30kΩ. Then R_
A resistor-divider can also be used to set the voltage of
one output from 0.8V to 1.2V. To do this, the other out-
put must be above 1.2V. Figure 6 shows an example of
this where OUT1 is set to 1V. To set the output voltage to
less than 1.2V, connect a resistor from FB1 to OUT1 (R1),
and from FB1 to OUT2 (R2). Select values of R1 and R2
such that current flowing through R1 and R2 is about
100µA and following equation is satisfied:
Dual, 180° Out-of-Phase, 1.4MHz, 750mA Step-
Down Regulator with POR and RSI/PFO
Figure 2. Timing Diagram
14
b
______________________________________________________________________________________
). Select the value of R_
a
), and connect a resistor from FB_ to GND
R
a
_
is calculated by:
R
a
1
=
=
R
R
_
2
Output Voltage Selection
b
1 2
V
×
.
OUT
Design Procedure
⎡
⎢
⎣
V
−
OUT
1 2
1
V
.
OUT
b
−
V
POR
RSI
V
PFO
, between 10kΩ and
4.04V
1 2
OUT
IN
−
.
2
1
⎤
⎥
⎦
~1V PKMAX
T
RESET
IN
T
by using an
D
= 1µs MIN
Each output is capable of continuously sourcing up to
750mA of current as long as the following condition is
met:
A 3.3µH to 6.8µH inductor with a saturation current of
800mA (min) is recommended for most applications.
For best efficiency, the inductor’s DC resistance should
be less than 100mΩ, and saturation current should be
greater than 1A. See Table 2 for recommended induc-
tors and manufacturers.
T
D
V
OUT
1
×
3.94V
I
OUT
1
V
+
IN
V
OUT
2
×
I
OUT
Inductor Value
2
≤ .
1 05
A