MAX1947ETA33+T Maxim Integrated Products, MAX1947ETA33+T Datasheet - Page 9

• Manufacturer Part Number: MAX1947ETA33+T
• Description: IC DC-DC CONV 3.3V 8-TDFN
• Manufacturer: Maxim Integrated Products
• Type: Step-Up (Boost)r

Specifications of MAX1947ETA33+T

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 3.3V
• Current - Output: 250mA
• Frequency - Switching: Up to 2MHz
• Voltage - Input: 0.7 ~ 3.6 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-TDFN Exposed Pad
• Power - Output: 1.95W
• Output Voltage: 3.3 V
• Output Current: 169 mA
• Input Voltage: 0.7 V to 3.6 V
• Supply Current: 70 uA
• Switching Frequency: 650 KHz
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: MAX1947ETA33+T

Calculate the maximum output current (I
inductor ripple current (I
follows:
Here, I
the LX switch’s off-time (0.25µs typ), and R
series resistance of the inductor.
I
D
I
RIPPLE
OUTMAX
=
LIM
⎡
⎢
⎢
⎢ ⎢
⎢
⎣
(
R DS ON PFET R
is the NFET current limit (800mA typ), t
=
⎡
⎢
⎢
⎢
⎢
⎣
(
V
R DS ON PFET R
(
=
OUT
V
V
(
OUT
OUT
I LIM
(
)
L t
_______________________________________________________________________________________
+
+
+
−
/
I
LIM
(
)
(
I RIPPLE
OFF
I LIM
I LIM
−
×
Step-Up DC-DC Converter with RESET
2
RIPPLE
(
+
−
−
R
DS ON NFET
+
DS ON PFET
I RIPPLE
I RIPPLE
(
R
(
) (
DS ON PFET
L
(
× −
2
2
) and duty cycle (D) as
)
)
1
(
−
)
V
D
BATT
)
)
)
2
)
×
×
+
+
R
OUTMAX
⎤
⎥
⎥
⎥
⎥
⎦
R
L
+
)
L
R
)
L
⎤
⎥
⎥
⎥
⎥
⎦
−
)
V
BATT
L
) using
OFF
is the
is
Low Input/Output Voltage
The MAX1947 is specifically designed for using small,
inexpensive, low-ESR ceramic capacitors. X5R and
X7R dielectrics are recommended when operating over
wide temperature ranges. Bypass the output of the
MAX1947 with 10µF when using maximum load cur-
rents. When using less than half the maximum load cur-
rent capability, the output capacitor can be reduced to
4.7µF. Bypass the input with a 2.2µF or larger ceramic
capacitor. Table 1 lists the suggested values for the
input and output capacitors for typical applications.
Careful PCB layout is important for minimizing ground
bounce and noise. Keep the IC’s GND pins and the
ground leads of the input and output filter capacitors
very close together. Connect GND and PGND directly
to the exposed paddle. In addition, keep all connec-
tions to the OUT and LX pins as short as possible. To
maximize output power and efficiency and minimize
output ripple voltage, use short, wide traces from the
input and output. A sample layout is available in the
MAX1947 evaluation kit.
TRANSISTOR COUNT: 5156
PROCESS: BiCMOS
PCB Layout and Grounding
Chip Information
Capacitor Selection
9