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Teilenummer | CAT4002A |
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Beschreibung | Constant Current LED Driver | |
Hersteller | ON Semiconductor | |
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Gesamt 11 Seiten CAT4002A, CAT4004A
Constant Current LED
Driver with 32 Dimming
Levels and Rset
Description
The CAT4002A and CAT4004A provide respectively two and four
matched low dropout current sources to drive LEDs. The CAT400XA
uses an external resistor RSET to set the current in the LED channels.
Each LED channel includes an individual control loop allowing the
device to handle a wide range of LED forward voltages while still
maintaining tight current matching.
The EN/DIM logic inputs supports device enable and a digital
dimming interface for setting the LED channel current with 32 linear
dimming levels.
LEDs can be powered directly from a Lithium−ion battery due to the
low dropout (50 mV at 20 mA) current sinks. The device is available
in the tiny 8−pad UDFN 2 mm x 2 mm package with a max height of
0.55 mm, as well as the 6−lead TSOT−23 and SC−70.
Features
• 2 and 4 LED Current Sinks with Tight Matching
• 32 Dimming Levels
• Low Dropout Driver 50 mV at 20 mA
• No Switching Noise
• Shutdown Current less than 1 mA
• LED Current set by External Resistor
• Dimming via 1−wire EZDimt Interface
• Thermal Shutdown Protection
• 6−lead TSOT−23, SC−70, and 8−pad UDFN 2 mm x 2 mm Packages
• These Devices are Pb−Free, Halogen Free/BFR Free and are RoHS
Compliant
Applications
• LCD Display Backlight
• Cellular Phones
• Digital Still Cameras
• Handheld Devices
VIN
2.4 V
to
5.5 V
CIN
1 mF
20 mA
LED1 LED2 LED3 LED4
One wire
programming
RSET
3.74 kW
VIN
EN/DIM
RSET
CAT4004A
GND
Figure 1. Typical Application Circuit
http://onsemi.com
UDFN−8
HU2G SUFFIX
CASE 517AW
TSOT23−6
TD SUFFIX
CASE 419AF
SC70−6
SD SUFFIX
CASE 419AD
PIN CONNECTIONS
1
EN/DIM
GND
LED1
LED2
VIN
RSET
LED4
LED3
CAT4004A
UDFN−8
1
EN/DIM
LED1
GND
RSET
VIN LED2
CAT4002A
TSOT23−6
1
EN/DIM
RSET
VIN
CAT4002A
SC70−6
(Top Views)
LED1
GND
LED2
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 11 of this data sheet.
© Semiconductor Components Industries, LLC, 2011
June, 2011 − Rev. 2
1
Publication Order Number:
CAT4002A/D
CAT4002A, CAT4004A
Table 6. PIN DESCRIPTIONS
Name
Function
EN/DIM
Device enable (active high) and dimming control
GND
Ground reference
LED1
LED1 cathode terminal
LED2
LED2 cathode terminal
LED3
LED3 cathode terminal (CAT4004A only)
LED4
LED4 cathode terminal (CAT4004A only)
RSET
Connect external RSET resistor to set the LED current
VIN Device supply input, connect to battery or supply
TAB Connect to GND on the PCB (CAT4004A only)
Pin Function
VIN is the supply pin for the charge pump. A small 1 mF
ceramic bypass capacitor is required between the VIN pin
and ground near the device. The operating input voltage
range is from 2.5 V to 5.5 V. Whenever the input supply falls
below the under−voltage threshold (2.0 V), all the LED
channels are disabled and the device enters shutdown mode.
EN/DIM is the enable and one wire dimming input for all
LED channels. Levels of logic high and logic low are set at
1.3 V and 0.4 V respectively. When EN/DIM is initially
taken high, the CAT400XA becomes enabled and the LED
channel current is set to the full scale according to the
resistor RSET. To place the device into “zero current”
shutdown mode, the EN/DIM pin must be held low for 3 ms
typical.
Block Diagram
LED1 to LED4 provide the internal regulated current for
each of the LED cathodes. There pins enter a high
impedance zero current state whenver the device is placed
in shutdown mode.
RSET is connected to the resistor (RSET) to set the full scale
current for the LEDs. The voltage at this pin is regulated to
0.6 V. The ground side of the external resistor should be star
connected back to the GND of the PCB. In shutdown mode,
the RSET input becomes high impedance.
GND is the ground reference for the device. The pin must be
connected to the ground plane on the PCB.
TAB (CAT4004A only) is the exposed pad underneath the
package. For best thermal performance, the tab should be
soldered to the PCB and connected to the ground plane.
VIN
VIN
RSET
Undervoltage
Lockout
Reference
Voltage
Current
Setting DAC
EN/DIM
Serial
Interface
100 kW
Register
4 Current Sink
Regulators
GND
Figure 15. CAT4004A Functional Block Diagram
http://onsemi.com
6
6 Page | ||
Seiten | Gesamt 11 Seiten | |
PDF Download | [ CAT4002A Schematic.PDF ] |
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