ST619LB
DC-DC converter regulated 5 V charge pump
Features
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■
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Regulated 5 V ±4 % charge pump
Output current guaranteed over temperature:
20 mA (V
I
≥
2 V), 30 mA (V
I
≥
3 V)
No inductors; very low EMI noise
Uses small, inexpensive capacitors
Logic controlled 1 µA max shut-down supply
current
Shut down disconnects load from input
Available in SO-8 and DIP-8 packages
SO-8
Description
The ST619LB is a step-up charge pump DC-DC
converter which delivers a regulated 5 V ±4 %
output at 30 mA and over temperature. The input
voltage range is 2 V to 3.6 V (two battery cells).
It requires only four external capacitor: two
0.22 µF flying capacitors, and 10 µF capacitors at
the input and output.
Low operating supply current (typ. 200 µA) make
the device ideal for small, portable and battery
powered applications. When shut down the load
is disconnected from the input and the supply
current is typically 0.02 µA. The ST619LB is
available in SO-8 package.
Table 1.
Device summary
Order codes
ST619LB
SO-8 (tape & reel)
ST619LBDR
November 2007
Rev. 4
1/16
www.st.com
16
ST619LB
Contents
1
2
3
Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Operating principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1
Shut down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4
5
6
7
Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1
7.2
7.3
Charge pump capacitors C1 and C2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Input and output capacitors C3 and C4 . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Layout consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8
9
Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2/16
ST619LB
Schematic
1
Figure 1.
Schematic
Schematic diagram
3/16
Pin configuration
ST619LB
2
Figure 2.
Pin configuration
Pin connections (top view)
Table 2.
Pin n°
1
2
3
4
5
6
7
8
Pin description
Symbol
C1+
IN
OUT
C2+
C2-
GND
SHDN
C1-
Name and function
Positive terminal for the first charge pump capacitor
Input supply voltage
5V output voltage. V
O
=0V when in shutdown mode.
Positive terminal for the second charge pump capacitor
Negative terminal for the second charge pump capacitor
Ground
Active high C-MOS logic level shutdown input. SHDN is connected to GND for normal
operation.
Negative terminal for the first charge pump capacitor
4/16
ST619LB
Operating principle
3
Operating principle
The ST619LB is able to provide a regulated 5 V output from a 2 V to 3.6 V (two battery cells)
input. Internal charge pump and external capacitors generate the 5 V output, eliminating the
need for inductors. The output voltage is regulated to 5 V, ±4 % by a pulse skipping
controller that turns on the charge pump when the output voltage begins to drop. To
maintain the greatest efficiency the internal charge pump of the device operates as a
voltage doubler when V
I
ranges from 3.0 V to 3.6 V and as a voltage triple when V
I
ranges
from 2.0 V to 2.5 V.
When V
I
ranges from 2.5 V to 3.0 V, the ST619LB switches between doubler and triple
mode on alternating cycles, making a 2.5 x V
I
charge pump. To further enhance the
efficiency over the input range, an internal comparator selects the higher of V
I
or V
O
to run
the ST619LB's circuitry. With V
I
= 2 V and I
O
= 20 mA the typical efficiency value is 80%.
In triple mode (see block diagram), when the S1 switches close, the S2 switches open and
capacitors C1 and C2 charge up to V
I
. On the second half of the cycle, C1 and C2 are
connected in series between IN and OUT when the S1 switches open and S2 switches
close. In the doubler mode only C2 is used. During one oscillator cycle, energy is transferred
from the input to the charge pump capacitors, and then from the charge pump capacitors to
the output capacitors and load. The number of cycles within a given time frame increases as
the load increases or as the input supply voltage decreases. In the limiting case, the charge
pumps operate continuously, and the oscillator frequency is nominally 500 kHz.
3.1
Shut down mode
The ST619LB enters low power shut down mode when SHDN is a logic high. In shut down
mode, OUT is disconnected from the IN and V
O
falls to 0V. The SHDN pin is connected to
ground for normal operation. SHDN is a CMOS compatible input.
5/16
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