EV-184 - Skyworks Solutions, Inc.

EVALUATION BOARD DATASHEET
EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Introduction
The AHK1421 evaluation board demonstrates functionality of the AHK1421 and its application as a white LED backlight
driver under AnalogicTech’s S2Cwire serial digital interface control.
The AHK1421 is a high frequency, high efficiency, constant-current boost converter driving six white LEDs in series
configuration. The input voltage is 2.7V to 5.5V, which is ideal for portable devices powered by single-cell lithium-ion/
polymer (Li-ion) batteries. The maximum LED current is set by an external resistor from 10 to 31mA. The AHK1421 is
programmable with the S²Cwire interface, using an onboard microcontroller which is capable of brightening and dimming the LEDs in 32 discrete steps.
This document describes the evaluation board and its accompanying user interface. A brief “Getting Started” section
is included to help the user to begin operating the evaluation board.
Board Pictures
(a) Top
(b) Bottom
Figure 1: AHK1421 Evaluation Board
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EVALUATION BOARD DATASHEET
EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Board Schematic
LX
DS1
L1
VOUT
10µH
U1
J1
AHK1421ICA
6
DC+
3
2
1
2.7~5.5V
J2
DC-
VIN
CIN
2.2µF
LX
OUT
EN/SET
4
GND
FB
1
D1
D2
5
COUT
2.2µF
D3
D4
3
D5
D6
2
RFB
12.5
AHK1421
White LED
Driver
R4
51k
V_MCU
EN/SET
R7 R8 R9
1k 1k 1k
UP
S2Cwire
Microcontroller
1
2
3
4
U2
PIC12F675
VDD
GP5
GP4
GP3
VSS
GP0
GP1
GP2
C1
0.1µF
8
7
6
5
R5
1k
LED1
Red
R6
330
LED2
Green
DOWN
CYCLE
Figure 2: AHK1421 Evaluation Board Schematic
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EV-184.2011.05.1.0
EVALUATION BOARD DATASHEET
EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Getting Started
Setup (Figure 3)
1. Connect an input power source (to supply between 2.7V and 5.5V) to the board by placing the jumper, J1 on the
left (Connects DC+ power to AHK1421).
2. Connect the DC+ power to the microcontroller VDD by using the jumper V_MCU.
3. Connect the EN/SET jumper to connect the microcontroller GPIOs to the AHK1421 EN/SET pins.
4. After all jumpers are in the correct position, apply power between 2.7V and 5.5V to the DC+ and DC- terminals to
power on the AHK1421 (U1) and microcontroller (U2). The red LED (LED1) will illuminate when the microcontroller
is powered. The green LED (LED2) will flicker when the three buttons to transfer S²C wire data for AHK1421 are
operated.
5. Use the UP, DOWN and CYCLE buttons to vary the brightness of the 6 white LEDs using the EN/SET serial data
S2Cwire interface
Figure 3: AHK1421 Evaluation Board Measurement Configuration
S2Cwire Control
Short the EN/SET jumper to receive S2Cwire data generated by the microcontroller according to the status of the three
buttons. The AHK1421 records the number of rising edges which control output current in EN/SET pin and change the
value of output current from 20mA to 0.4mA when RFB is 12.5Ω
•• UP button: The UP button increments the number of EN/SET rise edges from 1 to 32 each time this button is pushed.
By holding down the button for more than 0.6 seconds, the microcontroller enters auto-increment mode. The LED
will dim and wrap back after S2C wire data reaches 32.
•• DOWN button: The DOWN button decrements the number of EN/SET rise edges from 32 to 1 each time this button
is pushed. By holding down the button for more than 0.6 seconds, the microcontroller enters auto-decrement mode.
The LED will brighten and wrap back after S2Cwire data reaches 1.
•• CYCLE button: The button increments or decrements the number of EN/SET edges automatically and cyclically after
a single push according to the previous EN edges up or down event.
•• UP+DOWN+CYCLE button: EN/SET is set to 0V and the AHK1421 is shut down. All white LEDs are turned off.
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EVALUATION BOARD DATASHEET
EV-184
S2Cwire Controlled, Serial LED Boost Driver
ILED (mA)
AHK1421 EVAL :
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
S2Cwire Data
Figure 4: S2Cwire Dimming Control at Maximum LED Current (20mA max)
User Interface Functionality
Button(s)
UP
DOWN
CYCLE
UP+DOWN+CYCLE
Action
Effect
Increment the number of EN/SET edge; Toggles through the available
dimming level settings for the backlighting section.
Auto-increment the number of EN/SET edges up to 32 then wrap back
to 1.
Decrement the number of EN/SET edge; Toggles through the available
brightness level settings for the backlighting section.
Auto-decrement the number of EN/SET edges down to 1 then wrap
back to 32
Push/Release once
Push Hold 0.6 sec.+
Push/Release once
Push Hold 0.6 sec.+
Push/Release once or Push
Hold 0.6 sec.+
Push All Three and Hold
Auto-cycle in direction last set
Shut down
Table 1: User Interface Functionality
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EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Functional Testing and Evaluation
Operational Waveform
Figure 5 shows the waveform controlled by S2Cwire at 3.6V VIN when the code changes from 32 to 1.The ILED changes
from 0.4mA (2% IMAX) to 20mA (IMAX).
Channel
Signal
1
2
3
4
VOUT
EN/SET
ILED
IIN
Figure 5: Operational Waveform under S²Cwire Control.
Start up
Figure 6 shows the AHK1421 startup waveform after adding rising edge on EN/SET. Soft start control makes the input
current rise slowly.
Channel
Signal
1
2
3
4
SW
VOUT
ILED
IIN
Figure 6: Start Up Waveform.
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EVALUATION BOARD DATASHEET
EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Efficiency Curves
Figure7 shows that the maximum efficiency is about 85% under 4.2V input voltage. Consult the AHK1421 product
datasheet about the external diode selection.
90
88
86
84
82
80
Efficiency (%)
78
VIN = 3.6V
76
74
72
VIN = 4.2V
70
68
66
64
62
60
58
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
ILED (mA)
Figure 7: Efficiency Curve Waveforms.
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EV-184.2011.05.1.0
EVALUATION BOARD DATASHEET
EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Printed Circuit Board
(a) Top
(b) Bottom
Figure 8: AHK1421 Evaluation Board (not to Scale)
AHK1421 EVAL Board Component Listing
Component
Part Number
Description
U1
AHK1421ICA
U2
R6
RFB
R5, R7, R8, R9
R4
CIN
COUT
C1
D1, D2, D3, D4, D5, D6
PIC12F675
GRM188R60J225KE01
GRM21BR61H225KA73L
GRM188R71C104K
RS-0805UW
DS1
SS14L
L1
LED1
LED2
CYCLE, UP, DOWN
CDRH2D14-100
0805KRCT
0805KGCT
6*6*5
Chip RES
S2C controlled, serial LED boost driver IC,
TSOT23-6
8-bit CMOS, FLASH-Based uC;SOIC-8
RES 330Ω 1/4W 1% 0603 SMD
RES 12.5Ω 1/4W 1% 0603 SMD
RES 1KΩ 1/4W 1% 0603 SMD
RES 51KΩ 1/4W 1% 0603 SMD
Cap 2.2μF 0603 X5R 10V 10%
Cap 2.2μF 0805 X7R 50V 10%
Cap 0.1uF 0603 X7R 16V 10%
20mA White LED 0805
1.0AMP.Surface Mount Schottky Barrier
Rectifiers
POWER INDUCTOR 10μH SMD
Red LED 0805
Green LED 0805
12V 50mA Push button
Manufacturer
AnalogicTech
Microchip
Yageo
Murata
Realstar
TSC
Sumida
HB
E-LT
Table 2: AHK1421 Evaluation Board Bill of Materials.
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EVALUATION BOARD DATASHEET
EV-184
AHK1421 EVAL :
S2Cwire Controlled, Serial LED Boost Driver
Advanced Analogic Technologies, Inc.
3230 Scott Boulevard, Santa Clara, CA 95054
Phone (408) 737-4600
Fax (408) 737-4611
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights, or other intellectual
property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice. Except as provided in AnalogicTech’s terms and
conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty relating to the sale and/or use of AnalogicTech products including liability or warranties
relating to fitness for a particular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate
design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to
support this warranty. Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other
brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
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EV-184.2011.05.1.0