MAX679EUA Maxim Integrated Products, MAX679EUA Datasheet - Page 4

• 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

Regulated 3.3V Charge Pump
(Typical Operating Circuit with: V
otherwise noted.)
The MAX679 regulated charge pump has a 50% duty-
cycle clock. In phase one (charge phase), the charge-
transfer capacitor (C1) charges to the input voltage,
and output current is delivered by the output filter
capacitor (C
placed in series with the input and connects to the out-
put, transferring its charge to C
run continuously, this process would eventually gener-
ate an output voltage equal to two times the input volt-
age (hence the name “doubler”).
4
______________________________________________________________Pin Description
_______________Detailed Description
____________________________Typical Operating Characteristics (continued)
PIN
FSET = IN (1MHz)
_______________________________________________________________________________________
1
2
3
4
5
6
7
8
OUTPUT RIPPLE (2mA LOAD)
SHDN
NAME
PGND
FSET
GND
OUT
C1+
C1-
100 s/div
IN
OUT
). In phase two (transfer phase), C1 is
Set Charge-Pump Frequency Input. FSET = GND selects 330kHz and FSET = IN selects 1MHz. Do not leave
FSET unconnected.
Shutdown Input. The device shuts down, the output disconnects from the input, and the supply current
decreases to 1µA when SHDN is a logic low. Connect SHDN to IN for normal operation.
Supply Input. Connect to an input supply in the 1.8V to 3.6V range. Bypass IN to GND with a (C
capacitor.
Ground. Analog ground for internal reference and control circuitry.
Power Ground. Charge-pump current flows through this pin.
Negative Terminal of the Charge-Pump Capacitor
Positive Terminal of the Charge-Pump Capacitor
3.3V Power Output. Bypass OUT to GND with an output filter capacitor (see the Design Procedure section).
MAX679 TOC10
IN
V
50mV/div
AC COUPLED
OUT
= V
OUT
S HDN
. If the clock were to
= 2V, C
V
FSET = IN (1MHz)
IN
(1mA TO 10mA LOAD, V
= 3V
LOAD-TRANSIENT RESPONSE
IN
= 4.7µF, C1 = 0.33µF, C
100 s/div
The charge pump regulates by gating the oscillator on
and off as needed to maintain output regulation. This
method has low quiescent current, but to achieve
acceptable output ripple, C1 must be significantly
lower in value than C
The MAX679 soft-start circuitry prevents excessive cur-
rent from being drawn from the battery at start-up or
when the output is shorted. This is done by limiting the
charge pump to 1/10 the normal current until either the
output is in regulation or the first 4096 charge-pump
IN
FUNCTION
= 3V)
MAX679 TOC11
OUT
V
10mV/div
AC COUPLED
I
5mA/div
OUT
OUT
= 10µF, tested in-circuit, T
OUT
V
FSET = IN (1MHz)
IN
(1mA TO 10mA LOAD, V
= 2V
LOAD-TRANSIENT RESPONSE
.
Start-Up Sequence
50 s/div
A
= +25°C, unless
IN
= 2V)
OUT
MAX679 TOC12
/ 2)µF
V
10mV/div
AC COUPLED
I
5mA/div
OUT
OUT