MAX1673 Maxim, MAX1673 Datasheet - Page 8

• Manufacturer Part Number: MAX1673
• Description: Regulated / 125mA-Output / Charge-Pump DC-DC Inverter
• Manufacturer: Maxim

The expression for the ripple component predominantly
due to charge transfer is:
where C
values, ESR
C
ance (typically 3.5Ω, and f
ing frequency (typically 350kHz). If ESR
small, as is likely when ceramic capacitors are used,
V
large, as with low-cost tantalum capacitors, then V
PLE (ESR)
When operating in LIN mode, use the following equa-
tion to approximate peak-to-peak output voltage ripple:
where C
the output capacitor’s ESR, and f
oscillator frequency (typically 350kHz).
To ensure LIN mode stability over the entire tempera-
ture range, choose a low-ESR (no more than 100mΩ)
output capacitance using the following equation:
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.
8
© 1998 Maxim Integrated Products
Regulated, 125mA-Output,
Charge-Pump DC-DC Inverter
Table 1. Partial Listing of Capacitor Vendors
RIPPLE (TRANSFER)
OUT
_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
PRODUCTION METHOD
Surface-Mount Tantalum
V
Surface-Mount Ceramic
RIPPLE(ESR)
, R
V
V
RIPPLE(ESR)
RIPPLE
FLY
OUT
OUT
dominates.
C OUT = 75 x 10
COUT
and C
is the output capacitor value, ESR
is the MAX1673 open-loop output imped-
=
= 2
2 f
=
OSC
is the equivalent series resistance of
OUT
8
I
V
OUT
IN
V
dominates. If ESR is relatively
C
IN
f
– V
are their respective capacitance
OSC
OUT
- 6
f
– V
OSC
OUT
OSC
R1 + R2
OUT
R1
2I
MANUFACTURER
is the MAX1673 switch-
R
OUT
OUT
R
OSC
AVX
Matsuo
Sprague
AVX
Matsuo
2
ESR
OUT
ESR
I
(C
OUT
Printed USA
COUT
FLY
is the MAX1673
C
COUT
1
FLY
COUT
C
OUT
COUT
is very
)
RIP-
is
593D, 595D
SERIES
TPS
X7R
X7R
267
where C
the minimum oscillator frequency (250kHz). See Table
1 for a list of suggested capacitor suppliers.
The MAX1673’s high oscillator frequency requires good
layout technique, which ensures stability and helps
maintain the output voltage under heavy loads. Take
the following steps to ensure good layout:
• Mount all components as close together as possible.
• Place the feedback resistors R1 and R2 close to the
• Keep traces short to minimize parasitic inductance
• Use a ground plane.
TRANSISTOR COUNT: 386
SUBSTRATE CONNECTED TO: IN
___________________Chip Information
FB pin, and minimize the PC trace length at the FB
circuit node.
and capacitance.
is a registered trademark of Maxim Integrated Products.
OUT
is the output capacitor value, and f
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Layout Considerations
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