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UM1660 Schematic ( PDF Datasheet ) - Union Semiconductor

Teilenummer UM1660
Beschreibung Low Power DC/DC Boost Converter
Hersteller Union Semiconductor
Logo Union Semiconductor Logo 




Gesamt 15 Seiten
UM1660 Datasheet, Funktion
UM1660
Low Power DC/DC Boost Converter
UM1660S SOT23-5
UM1660DA DFN6 2.0×2.0
General Description
The UM1660 is a PFM controlled step-up DC-DC converter with a switching frequency up to
1MHz. The device is ideal to generate output voltage for small to medium LCD bias supplies and
white LED backlight supplies from a single cell Li-Ion battery. The part can also be used to
generate standard 3.3V/5V to 12V power conversions.
With a high switching frequency of 1MHz, a low profile and small board area solution can be
achieved using a chip coil and an ultra small ceramic output capacitor. The UM1660 has an
internal 400mA switch current limit, offering lower output voltage ripple. The low quiescent
current (typically 36µA) together with an optimized control scheme, allows device operation at
very high efficiencies over the entire load current range.
Applications
Features
LCD Bias Supply
White LED Supply for LCD Backlights
Digital Still Camera
PDAs, Organizers and Handheld PCs
Cellular Phones
Standard 3.3V/5V to 12V Conversion
2.0V to 6.0V Input Voltage Range
Adjustable Output Voltage up to 28V
400mA Internal Switch Current
Up to 1MHz Switching Frequency
36µA Typical No Load Quiescent Current
1µA Maximum Shutdown Current
Internal Soft-Start
Available in Tiny SOT23-5 and DFN6
2.0×2.0 Packages
Pin Configurations
Top View
(Top View)
54
SW 1
5 VIN
PHO
GND 2
FB 3
4 EN
(Top View)
VIN 1
GND 2
EN 3
6 SW
5 NC
4 FB
123
M: Month Code
UM1660S
SOT23-5
AAG
Marking Pin1
M: Month Code
UM1660DA
DFN6 2.0×2.0
________________________________________________________________________
http://www.union-ic.com Rev.05 Feb.2014
1/15






UM1660 Datasheet, Funktion
UM1660
V IN= 2.0 - 6 V
R3
47k
L1
10µH
D1
VOUT
18V/10mA
C1
4.7µF
GPIO
VIN SW
UM1660
EN FB
GND
C2
1µF
R1
2.2M
R2
160k
CFF
22pF
C2
0.1µF
(Optional)
Figure 2. Disconnect the input from the output during shutdown using external transistor
Under-voltage Lockout
An under-voltage lockout prevents misoperation of the device at input voltages below typical 1.5V.
When the input voltage is below the under-voltage threshold the main switch is turned off.
Typical Application Circuit
VIN= 2.0 - 6V
L1
10µH
D1
VOUT
CIN
4.7µF
VIN SW
UM1660
EN FB
GND
R1
R2
CFF
COUT
1µF
Figure 3. Standard DC/DC Boost Supply
The output voltage is calculated as:
Vout 1.233 (1 R1)
R2
We can use a PWM signal on the enable pin of UM1660 to adjust the white LED brightness (see
figure 4 below). When adding the PWM signal to EN pin, the UM1660 is turned on or off by the
PWM signal, so the LEDs operate at either zero or full current. The average LED current
increases proportionally with the duty cycle of the PWM signal. The magnitude of the PWM
signal should be higher than the minimum enable voltage of EN pin (1.3V) and lower than the Vin,
in order to let the dimming control perform correctly. The frequency range of the PWM signal is
from 50Hz to 10 kHz.
________________________________________________________________________
http://www.union-ic.com Rev.05 Feb.2014
6/15

6 Page









UM1660 pdf, datenblatt
UM1660
Layout Considerations
High switching frequencies and relatively large peak currents make the PCB layout a very
important part of design. Good design minimizes excessive EMI on the feedback paths and
voltage gradients in the ground plane, resulting in a stable and well-regulated output. Good layout
for the UM1660 can be implemented by following a few simple design rules.
1. The input capacitor should be placed as close as possible to the input pin for good input
voltage filtering.
2. The inductor and diode should be placed as close as possible to the switch pin to minimize
the noise coupling into other circuits.
3. The feedback network should be routed away from the inductor. The feedback pin and
feedback network should be shielded with a ground plane or trace to minimize noise coupling
into this circuit.
4. Wide traces should be used for connections in bold as shown in the Figure below. A star
ground connection or ground plane minimizes ground shifts and noise.
V IN
L1 D1
VOUT
VIN SW
R1 CFF
CIN UM1660
COUT
EN FB
GND
R2
________________________________________________________________________
http://www.union-ic.com Rev.05 Feb.2014
12/15

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