MAX1673 Maxim, MAX1673 Datasheet - Page 6

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

The MAX1673 new-generation, high-output-current,
regulated charge-pump DC-DC inverter provides up to
125mA. Designed specifically for compact applica-
tions, a complete regulating circuit requires only three
small capacitors and two resistors. The MAX1673
employs On-Demand™ regulation circuitry, providing
output regulation modes optimized for either lowest out-
put noise or lowest supply current. In addition, the
MAX1673 includes shutdown control.
Regulated, 125mA-Output,
Charge-Pump DC-DC Inverter
Figure 1. Standard Application Circuit
6
______________________________________________________________Pin Description
INPUT
PIN
_______________________________________________________________________________________
5.0V
1
2
3
4
5
6
7
8
LIN
ON
2.2 F
C
FLY
10 F
C
SKIP
OFF
IN
LIN/SKIP
NAME
CAP+
SHDN
CAP-
GND
OUT
FB
IN
4
2
3
1
SHDN
CAP+
CAP-
LIN/SKIP
Regulation-Mode Select Input. Driving LIN/SKIP high or connecting it to IN selects LIN mode, with regula-
tion accomplished by modulating switch resistance. Driving LIN/SKIP low or connecting it to GND selects
Skip mode, where the device regulates by skipping charge-pump pulses.
Positive Terminal of Flying Capacitor
Negative Terminal of Flying Capacitor
Shutdown Control Input. Drive SHDN low to shut down the MAX1673. Connect SHDN to IN for normal
operation. OUT connects to GND through a 1Ω (typical) resistor in shutdown mode.
Inverting Charge-Pump Output
Feedback Input. Connect FB to a resistor-divider from IN (or other reference source) to OUT for regulated
output voltages (Figures 1 and 4).
Ground
Power-Supply Positive Voltage Input
Detailed Description
MAX1673
IN
8
GND
OUT
FB
7
6
5
C
22 F
OUT
R1
100k
R1
60.4k
OUTPUT
-3V
In Linear (LIN) mode or when heavily loaded in Skip
mode, the charge pump runs continuously at 350kHz.
During one-half of the oscillator period, switches S1 and
S2 close (Figure 2), charging the transfer capacitor
(C
IN). During the other half cycle, switches S3 and S4
close (Figure 3), transferring the charge on C
output capacitor (CAP+ = GND, CAP- = OUT).
Figure 3. Transferring Charge on C
Figure 2. Charging C
FLY
350kHz
350kHz
FUNCTION
) to the input voltage (CAP- = GND, and CAP+ =
IN
IN
S1
S2
S1
S2
FLY
C
C
FLY
FLY
CAP+
CAP-
CAP+
CAP-
FLY
S3
S4
S3
S4
to C
OUT
C
C
OUT
OUT
FLY
to the
OUT
OUT