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CAT3614
4-Channel 1-Wire LED Driver in 3x3mm Package
FEATURES
Drives up to 4 LED channels 1-wire EZDimTM Programmable LED Current Accurate 1mA Dimming Level Power efficiency up to 91% Fractional pump 1x/1.5x Low noise input ripple Fixed High Frequency Operation 1MHz "Zero" Current Shutdown Mode Soft start and current limiting Short circuit protection Thermal shutdown protection 12-lead TDFN 3mm x 3mm package
DESCRIPTION
The CAT3614 is a high efficiency 1x/1.5x fractional charge pump with programmable dimming current in four LED channels. To ensure uniform brightness in LCD backlight applications, each LED channel delivers an accurate regulated current. Low noise and input ripple is achieved by operating at a constant switching frequency of 1MHz which allows the use of small external ceramic capacitors. The 1x/1.5x fractional charge pump supports a wide range of input voltages from 3V to 5.5V with efficiency up to 91%, and is ideal for Li-Ion battery powered devices. The EN/DIM logic input provides a 1-wire EZDimTM interface for dimming control of the LEDs. When enabled, a series of clock pulses reduces the LED brightness in 1mA steps on each negative going edge. Currents from 0mA to 31mA are supported. The device is available in the tiny 12-lead thin DFN 3mm x 3mm package with a max height of 0.8mm.
APPLICATIONS
LCD Display Backlight Cellular Phones Digital Still Cameras Handheld Devices
ORDERING INFORMATION
Part Number CAT3614HS2-T2 CAT3614HV2-T2 Package TDFN-12 3x3 TDFN-12 3x3 Green Quantity per Reel 2000 2000 Package Marking HAAB HAAA
Pin Configuration
Top View
Typical Application Circuit
12-lead TDFN 3mm x 3mm
Note: Unused LED channels must be connected to VOUT.
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(c) 2006 Catalyst Semiconductor, Inc.
Doc. No. 25095, Rev. 01
Characteristics subject to change without notice
CAT3614
ABSOLUTE MAXIMUM RATINGS
Parameter VIN, LEDx voltage VOUT, C1, C2 voltage EN/DIM voltage Storage Temperature Range Junction Temperature Range Lead Temperature Rating 6 7 VIN + 0.7V -65 to +160 -40 to +125 300 Unit V V V C C C
RECOMMENDED OPERATING CONDITIONS
Parameter VIN Ambient Temperature Range ILED per LED pin Total Output Current Range 3 to 5.5 -40 to +85 0 to 31 0 to 124 Unit V C mA mA
Typical application circuit with external components are shown on page 1.
ELECTRICAL OPERATING CHARACTERISTICS (over recommended operating conditions unless specified otherwise) VIN = 3.6V, EN = High, ambient temperature of 25C. Symbol Parameter Conditions Min Typ Max IQ Quiescent Current 0.3 0.5 1 1x mode, no load 1.5x mode, no load 1 3 8
IQSHDN ILED-ACC ILED-DEV ROUT FOSC ISC_MAX IIN_MAX IEN/DIM VHI VLO TSD THYS VUVLO Shutdown Current LED Current Accuracy LED Channel Matching Output Resistance (open loop) Charge Pump Frequency Output short circuit Current Limit Input Current Limit EN/DIM Pin Input Leakage Logic High Level Logic Low Level Thermal Shutdown Thermal Hysteresis Undervoltage lock out (UVLO) threshold VOUT < 0.5V 1x mode, VOUT > 1V VEN = 0V 1mA ILED 31mA (ILED - ILEDAVG) / ILEDAVG 1x mode, IOUT = 100mA 1.5x mode, IOUT = 100mA 0.8 30 200 -1 1.3 145 10 1.7 165 20 2 3 3 0.4 2.6 1 60 300 1 8 7 1 7 1.3 100 600 1 0.4 175 30 2.4
Unit mA mA A % % MHz mA mA A V V C C V
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(c) 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3614
Recommended EN/DIM Timing For 3V VIN 5.5V, over full ambient temperature range -40 to +85C. Symbol Parameter TSETP TLO THI TOFF TD TDEC EN/DIM setup from shutdown EN/DIM program low time EN/DIM program high time EN/DIM low time to shutdown LED current enable LED current decrement Conditions Min 10 0.3 0.3 1.5 40 0.1 200 Typ Max Unit s s s ms s s
Figure 1. LED Dimming Timing Diagram
(c) 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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CAT3614
Typical Characteristics
VIN = 3.6V, IOUT = 80mA (4 LEDs at 20mA), C1 = C2 = CIN = COUT = 1F, TAMB = 25C unless otherwise specified. Efficiency vs. Input Voltage (4 LEDs)
100 20mA per LED 90 EFFICIENCY [%] 80 70 60 50 40 4.2 4.0 3.8 3.6 3.4 3.2 INPUT VOLTAGE [V] 3.0 1.5x mode 10mA per LED
EFFICIENCY [%]
Efficiency vs. Total LED Current (4 LEDs)
100
1x mode
90 80 70 60 50 40 0
VIN = 4V (1x mode)
VIN = 3.2V (1.5x mode)
25
50
75
100
125
TOTAL LED CURRENT [mA]
Quiescent Current vs. Input Voltage (1x mode)
0.8 QUIESCENT CURRENT [mA] .
Quiescent Current vs. Temperature (1x mode)
0.8 QUIESCENT CURRENT [mA]
0.6
0.6
0.4 4 LEDs OFF 0.2
0.4 4 LEDs OFF 0.2
0.0 3.0 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] 4.2
0.0 -40 0 40 80 TEMPERATURE [C] 120
Quiescent Current vs. Input Voltage (1.5x mode)
QUIESCENT CURRENT [mA] . 6.0 5.0 4.0 3.0 2.0 1.0 0.0 3.0 3.2 3.4 3.6 3.8 4.0 4.2 INPUT VOLTAGE [V] 4 LEDs OFF
Quiescent Current vs. Temperature (1.5x mode)
6.0 QUIESCENT CURRENT [mA] 5.0 4.0 3.0 2.0 4 LEDs OFF 1.0 0.0 -40 0 40 80 TEMPERATURE [C] 120
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(c) 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3614
Typical Characteristics
VIN = 3.6V, IOUT = 80mA (4 LEDs at 20mA), C1 = C2 = CIN = COUT = 1F, TAMB = 25C unless otherwise specified. LED Current Change vs. Input Voltage
5.0 LED CURRENT CHANGE [%] .
LED CURRENT CHANGE [%]
LED Current Change vs. Temperature
5.0 4.0 3.0 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 -5.0 -40 -20 0 20 40 60 TEMPERATURE [C] 80
4.0 3.0 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 -5.0 3.0 3.2 3.4 3.6 3.8 4.0 4.2 INPUT VOLTAGE [V] 1.5x Mode 1x Mode
Oscillator Frequency vs. Input Voltage
1.3 CLOCK FREQUENCY [MHz] 1.2 1.1 1.0 4 LEDs at 20mA 0.9 0.8 0.7 3.0 3.2 3.4 3.6 3.8 INPUT VOLTAGE [V] 4.0
Oscillator Frequency vs. Temperature
1.3 CLOCK FREQUENCY [MHz] 1.2 1.1 1.0 0.9 0.8 0.7 -40 0 40 80 TEMPERATURE [C] 120
Output Resistance vs. Input Voltage (1x mode)
1.0 OUTPUT RESISTANCE [] . 0.8 0.6 0.4 0.2 0.0 3.0 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] 4.2
OUTPUT RESISTANCE [] .
Output Resistance vs. Input Voltage (1.5x mode) 4.0
3.5 3.0 2.5 2.0 1.5 1.0 3.0 3.2 3.4 3.6 3.8 4.0 INPUT VOLTAGE [V] 4.2
(c) 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. 25095, Rev. 01
CAT3614
Typical Characteristics
VIN = 3.6V, IOUT = 80mA (4 LEDs at 20mA), C1 = C2 = CIN = COUT = 1F, TAMB = 25C unless otherwise specified. Power Up with 4 LEDs at 15mA (1x Mode) Power Up with 4 LEDs at 15mA (1.5x Mode)
Enable Power Down Delay (1x Mode)
Enable Power Down Delay (1.5x Mode)
Switching Waveforms in 1.5x Mode
Operating Waveforms in 1x Mode
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(c) 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3614
Typical Characteristics
VIN = 3.6V, IOUT = 80mA (4 LEDs at 20mA), C1 = C2 = CIN = COUT = 1F, TAMB = 25C unless otherwise specified. Enable and Output Current Dimming Waveforms Line Transient Response (3.6V to 5.5V) 1x Mode
Enable High Minimum Program Time vs. Temperature
200 MINIMUM TIME [nS] . 160
Enable Low Minimum Program Time vs. Temperature
200 VIN = 3.5V MINIMUM TIME [nS] .
VIN = 3.5V 120 80 VIN = 4.2V 40 0 -40 0 40 80 TEMPERATURE [C] 120
160 120 VIN = 4.2V 80 40 0 -40 0 40 80 120 TEMPERATURE [C]
Enable Voltage Threshold vs. Temperature
1.2 ENABLE VOLTAGE [V]
OUTPUT VOLTAGE [V] 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 0
Foldback Current Limit
1.0 0.8 0.6 0.4 0.2 0.0 -40 0 40 80 120 TEMPERATURE [C]
1x Mode VIN = 3.5V
100 200 300 OUTPUT CURRENT [mA]
400
(c) 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. 25095, Rev. 01
CAT3614
PIN DESCRIPTIONS
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 TAB Name VIN C1+ C1C2C2+ GND LED1 LED2 LED3 LED4 EN/DIM VOUT TAB Function Supply voltage. Bucket capacitor 1 terminal Bucket capacitor 1 terminal Bucket capacitor 2 terminal Bucket capacitor 2 terminal Ground reference LED1 cathode terminal (if not used, connect to VOUT)1 LED2 cathode terminal (if not used, connect to VOUT)1 LED3 cathode terminal (if not used, connect to VOUT)1 LED4 cathode terminal (if not used, connect to VOUT)1 Device enable (active high) and dimming control input Charge pump output connected to the LED anodes Connect to GND on the PCB
Note: (1) LED1, LED2, LED3, LED4 pins should not be left floating. They should be connected to the LED cathode, or tied to VOUT pin if not used.
PIN FUNCTION
VIN is the supply pin for the charge pump. A small 1F ceramic bypass capacitor is required between the VIN pin and ground near the device. The operating input voltage range is from 2.2V to 5.5V. Whenever the input supply falls below the undervoltage threshold (2V) all LEDs channels will be automatically disabled. EN/DIM is the enable and dimming control logic input for all LED channels. Guaranteed levels of logic high and logic low are set at 1.3V and 0.4V respectively. When EN/DIM is initially taken high, the device becomes enabled and all LED currents remain at 0mA. The falling edge of the first pulse applied to EN/DIM sets all LED currents to their full scale of 31mA. On each consecutive falling edge of the pulse applied to EN/DIM, the LED current is decreased by 1mA step. On the 32nd pulse, the LED current is set to zero. The next pulse on EN/DIM resets the current back to their full scale of 31mA. To place the device into zero current shutdown mode, the EN/DIM pin must be held low for 1.5ms or more. VOUT is the charge pump output that is connected to the LED anodes. A small 1F ceramic bypass capacitor is required between the VOUT pin and ground near the device. GND is the ground reference for the charge pump. The pin must be connected to the ground plane on the PCB. C1+, C1- are connected to each side of the 1F ceramic bucket capacitor C1. C2+, C2- are connected to each side of the 1F ceramic bucket capacitor C2. LED1 to LED4 provide the internal regulated current for each of the LED cathodes. These pins enter a high impedance zero current state whenever the device is placed in shutdown mode. In applications using less than four LEDs, all unused channels should be wired directly to VOUT. This ensures the channel is automatically disabled dissipating less than 200A. TAB 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.
Doc. No. 25095, Rev. 01
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(c) 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3614
BLOCK DIAGRAM
Figure 2. CAT3614 Functional Block Diagram
BASIC OPERATION
At power-up, the CAT3614 starts operating in 1x mode where the output will be approximately equal to the input supply voltage (less any internal voltage losses). If the output voltage is sufficient to regulate all LED currents the device remains in 1x operating mode. If the input voltage is insufficient or falls to a level where the regulated currents cannot be maintained, the device automatically switches (after a fixed delay of 400s) into 1.5x mode. In 1.5x mode, the output is approximately equal to 1.5 times the input supply voltage (less any internal voltage losses). The above sequence is repeated each and every time the chip is powered-up or is taken out of shutdown mode (via EN/DIM pin).
(c) 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. 25095, Rev. 01
CAT3614
LED Current Setting Figure 1 shows the timing diagram necessary at the EN/DIM input for setting the LED currents. The EN/DIM set up time requires the signal to be held high for 10s or longer to ensure the initialization of the driver at power-up. Each subsequent pulse on the EN/DIM (300ns to 200s pulse duration) steps down the LED current from full scale of 31mA to zero with a 1mA resolution. Consecutive pulses should be separated by 300ns or longer. Pulsing beyond the 0mA level restores the current level back to full scale and the cycle repeats. Pulsing frequencies from 5kHz up to 1MHz can be supported during dimming operations. When the EN/DIM is held low for 1.5ms or more, the CAT3614 enters the shutdown mode and draws "zero" current. For applications with three LEDs or less, any unused LED pins should be tied to VOUT, as shown on Figure 3. The driver enters a thermal shutdown mode as soon as the die temperature exceeds about +165C. When the device temperature drops down by about 20C, the device resumes normal operation. External Components The driver requires a total of four external 1F ceramic capacitors: two for decoupling input and output, and two for the charge pump. Both capacitor types X5R and X7R are recommended for the LED driver application. In the 1.5x charge pump mode, the input current ripple is kept very low by design, and an input bypass capacitor of 1F is sufficient. In 1x mode, the device operating in linear mode does not introduce switching noise back onto the supply. Recommended Layout In 1.5x charge pump mode, the driver switches internally at a high frequency of 1MHz. It is recommended to minimize trace length to all four capacitors. A ground plane should cover the area under the driver IC as well as the bypass capacitors. Short connection to ground on capacitors Cin and Cout can be implemented with the use of multiple vias. A copper area matching the TDFN exposed pad (GND) must be connected to the ground plane underneath. The use of multiple vias improves the package heat dissipation.
Protection Mode
If an LED becomes open-circuit, the output voltage VOUT is internally limited to about 5.5V. This is to prevent the output pin from exceeding its absolute maximum rating.
Figure 3. Three LED Application
Figure 4. Single Flash LED Application
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(c) 2006 Catalyst Semiconductor, Inc. Characteristics subject to change without notice
CAT3614
PACKAGE DRAWING AND DIMENSIONS Thin DFN 12-Lead 3mm X 3mm, 0.45mm Pitch
RECOMMENDED LAND PATTERN
Dimensions in millimeters
(c) 2006 Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
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Doc. No. 25095, Rev. 01
REVISION HISTORY
Date 02/09/2006 07/21/06 Rev. 00 01 Reason Initial Release Update Typical Application Circuit Update Pin Descriptions Update Electrical Operating Characteristics
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Document No: 25095 Revision: 01 Issue date: 07/21/2006

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