ST ST619LB User Manual
DC-DC converter regulated 5 V charge pump
Features
■ Regulated 5 V ±4 % charge pump
■ Output current guaranteed over temperature:
20 mA (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
≥ 2 V), 30 mA (VI ≥ 3 V)
I
ST619LB
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 SO-8 (tape & reel)
ST619LB ST619LBDR
November 2007 Rev. 4 1/16
www.st.com
16
ST619LB
Contents
1 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 Pin configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3 Operating principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Shut down mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6 Typical performance characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.1 Charge pump capacitors C1 and C2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.2 Input and output capacitors C3 and C4 . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7.3 Layout consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2/16
ST619LB Schematic
1 Schematic
Figure 1. Schematic diagram
3/16
Pin configuration ST619LB
2 Pin configuration
Figure 2. Pin connections (top view)
Table 2. Pin description
Pin n° Symbol Name and function
1 C1+ Positive terminal for the first charge pump capacitor
2 IN Input supply voltage
3 OUT 5V output voltage. V
4 C2+ Positive terminal for the second charge pump capacitor
5 C2- Negative terminal for the second charge pump capacitor
6 GND Ground
7 SHDN
8 C1- Negative terminal for the first charge pump capacitor
Active high C-MOS logic level shutdown input. SHDN is connected to GND for normal
operation.
=0V when in shutdown mode.
O
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
from 2.0 V to 2.5 V.
ranges from 3.0 V to 3.6 V and as a voltage triple when VI ranges
I
When V
ranges from 2.5 V to 3.0 V, the ST619LB switches between doubler and triple
I
mode on alternating cycles, making a 2.5 x V
efficiency over the input range, an internal comparator selects the higher of V
the ST619LB's circuitry. With V
In triple mode (see block diagram), when the S1 switches close, the S2 switches open and
capacitors C1 and C2 charge up to V
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
ground for normal operation. SHDN is a CMOS compatible input.
charge pump. To further enhance the
I
= 2 V and IO = 20 mA the typical efficiency value is 80%.
I
. On the second half of the cycle, C1 and C2 are
I
falls to 0V. The SHDN pin is connected to
O
or VO to run
I
5/16
Loading...