MAX679EUA Maxim Integrated Products, MAX679EUA Datasheet - Page 6

• Manufacturer Part Number: MAX679EUA
• Description: Charge Pumps
• Manufacturer: Maxim Integrated Products

Specifications of MAX679EUA

• Function: Step Up
• Output Voltage: 3.3 V
• Output Current: 20 mA
• Maximum Operating Temperature: + 85 C
• Package / Case: uMAX-8
• Minimum Operating Temperature: - 40 C
• Mounting Style: SMD/SMT

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
6
6 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 [phone]
6 ___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 [phone]
© 1997 Maxim Integrated Products
© 1997 Maxim Integrated Products
© 1997 Maxim Integrated Products
Regulated 3.3V Charge Pump
cycles (about 4ms) have elapsed. The start-up
sequence begins at power-up, when exiting shutdown,
or when recovering from a short circuit. If V
than the 1.6V UVLO threshold, the device remains shut
down and ignores a high SHDN input.
Optimize the charge-pump circuit for size, quiescent
current, and output ripple by properly selecting the
operating frequency and capacitors C
C
For lowest output ripple, select 1MHz operation (FSET
= IN). In addition, increasing C
further reduce ripple. For highest efficiency, select
330kHz operation (FSET = GND) and select the largest
practical values for C
30-to-1 ratio. See Table 1 for some suggested values
and the resulting output ripple.
Note that the capacitors must have low ESR (<20mΩ)
to maintain low ripple. Currently, only ceramic capaci-
tors can provide such low ESR; therefore, the output fil-
ter capacitors should be a combination of a 1µF
ceramic capacitor and a 10µF tantalum capacitor.
Set the frequency to 1MHz by connecting FSET to IN.
Table 1 shows typical external component values.
Table 2. Manufacturers of Low-ESR Capacitors
__________________Design Procedure
OUT
Surface-Mount
Tantalum Capacitors
Surface-Mount
Ceramic Capacitors
___________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 [phone]
.
PRODUCTION
METHOD
OUT
and C1 while maintaining a
MANUFACTURER
OUT
Sprague
Matsuo
Matsuo
AVX
AVX
relative to C1 will
Smallest Size
Printed USA
Printed USA
Printed USA
IN
, C1, and
IN
is less
TPS series
267 series
593D, 595D series
X7R
X7R
CAPACITORS
Table 1. External Component Selection
Place C1, C
PGND and GND with a short trace.
Charge-pump efficiency is best at low frequency
(330kHz). The theoretical maximum efficiency is given
in the following equation:
Gate-charge losses amount to approximately 1mA from
the output at full switching frequency (about 5% to 7%
loss).
TRANSISTOR COUNT: 819
SUBSTRATE CONNECTED TO GND
___________________Chip Information
Theoretical maximum efficiency = V
V
(V)
2
2
2
2
3
3
3
3
IN
is a registered trademark of Maxim Integrated Products.
is a registered trademark of Maxim Integrated Products.
is a registered trademark of Maxim Integrated Products.
OUT
(µF)
0.33
0.33
0.33
0.33
[phone]
[phone]
[phone]
[phone]
[phone]
C1
0.1
0.1
0.1
0.1
, and C
PHONE
C
(µF)
IN
3.3
3.3
3.3
3.3
OUT
10
10
10
10
close to the IC. Connect
PC Board Layout
FSET
330k
330k
330k
330k
(Hz)
1M
1M
1M
1M
[phone]
[phone]
[phone]
[phone]
[phone]
OUT
FAX
Efficiency
/ (2 x V
Vp-p
(mV)
14
16
22
27
56
72
89
7
IN
)