General Description
The MAX8678 evaluation kit (EV kit) is a fully assembled
and tested printed-circuit board (PCB) for evaluating
the MAX8678 white LED charge pump with mono class
AB audio amplifier. The MAX8678 EV kit drives up to
four LEDs for backlighting. In addition, the EV kit is able
to drive a combined loudspeaker/earpiece speaker for
the mono audio amplifier. An on-board pulse generator
provides an easy way to evaluate the MAX8678’s ampli-
fier gain adjustment and LED dimming.
Features
♦High-Efficiency White LED Charge Pump
Individual Adaptive Supply for Each LED
24mA to 0.1mA Dimming Range
Low 50µA (typ) Quiescent Current
♦Mono Class AB Loudspeaker Amplifier
1.1W RMS Mono Output (8Ω, VIN = 5V)
Low 0.004% THD+N at 1kHz
High 90dB PSRR at 1kHz
Fully Differential Inputs
-9dB to +18dB Gain Settings in 3dB Steps
Low Quiescent Current
♦2.7V to 5.5V Supply Voltage Range
♦Thermal Shutdown, Open- and Short-Circuit
Protections
♦Fully Assembled and Tested
♦16-Pin, 3mm x 3mm Thin QFN IC Package
Evaluates: MAX8678
MAX8678 Evaluation Kit
________________________________________________________________
Maxim Integrated Products
1
19-4084; Rev 0; 3/08
Component List
For pricing, delivery, and ordering information, please contact Maxim Direct 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Ordering Information
+
Denotes lead-free and RoHS-compliant.
PART TYPE
MAX8678EVKIT+ EV Kit
DESIGNATION QTY DESCRIPTION
C1, C2, C4, C5,
C12, C13 6
1µF ±10%, 6.3V X5R ceramic
capacitors (0402)
Murata GRM155R60J105K
TDK C1005X5R0J105K
C3, C7, C8 3
0.1µF ±10%, 10V X5R ceramic
capacitors (0402)
TDK C1005X5R1A104K
C6 1
4.7µF ±10%, 6.3V X5R ceramic
capacitor (0603)
Murata GRM188R60J475K
TDK C1608X5R0J475K
C9, C11 2
10pF ±5%, 50V C0G ceramic
capacitors (0402)
TDK C1005C0G1H100D
D1–D4 4 White LEDs
Nichia NSCW215T
D5, D6 2 Green LEDs (0603)
Panasonic LNJ308G8TRA
J1 0 Not installed, 10-pin (2 x 5) header,
0.1in spacing
JU1, JU7 2 3-pin headers
JU2–JU5 4 2-pin headers
JU6 0 Not installed, PCB short
DESIGNATION QTY DESCRIPTION
R1, R2 2 470k
Ω
±5% resistors (0402)
R3, R4 2 220
Ω
±5% resistors (0402)
R5 1 10k
Ω
±5% resistor (0402)
S1–S5 5 Momentary pushbutton switches
Panasonic EVQ-PHP03T
U1 1
White LED charge pump with mono
C l ass AB aud i o am p l i fi er ( 16 thi n QFN )
Maxim MAX8678ETE+
(Top Mark: AFF)
U2 1
M axi m l ow - p ow er LC D m i cr ocontr ol l er
(68 QFN)
MAXQ2000-RAX+
U3 1
Maxim ultra-low-noise LDO linear
regulator (5 SC70)
MAX8511EXK25+
(Top Mark: ADV)
Y1 1
16MHz crystal
Citizen HC49US16.000MABJ-U
ECS ECS-160-20-4X
Vishay XT9S20ANA16M
Y2 0 N ot i nstal l ed , 32.768kH z cr ystal ( 1206)
— 6 Shunts, 2 position
— 1 PCB: MAX8678 Evaluation Kit+
µ
Evaluates: MAX8678
Quick Start
Recommended Equipment
Before beginning, the following equipment is needed:
• 2.7V to 5.5V power supply or battery able to deliver
1.5A
• Audio source (e.g., CD player, MP3 player, etc.)
•4Ω/8Ωspeaker
Procedure
The MAX8678 EV kit is fully assembled and tested.
Follow the steps below to verify board operation.
Caution: Do not turn on the power supply until all
connections are completed.
1) Preset the power supply to between 2.7V and 5.5V.
2) Turn off the power supply. Do not turn on the power
supply until all connections are completed.
3) Turn off the audio source.
4) Verify that shunts on JU2–JU5 are installed (if the
audio source does not have a bias voltage compati-
ble with the MAX8678, remove the shunts from JU2
and JU3 to use the input filter capacitors). See
Table 1 for jumper positions.
5) Connect the speaker across OUT+ and OUT- out-
put pads on MAX8678 EV kit.
6) Connect the audio source to IN+/IN- for differential
audio source and to IN+ for single-ended audio
input source.
7) Set JU1 to select a differential or single-ended input
(JU2 and JU3 must be removed when using a sin-
gle-ended input).
8) Set JU7 to IN1.
9) Connect the power-supply positive terminal to the
IN1 pad.
10) Connect the power-supply negative terminal to the
GND1 pad.
11) Turn on the power supply and the audio source.
12) Press switch S2 once.
13) Verify that the white LEDs are dimly lit.
14) Repeatedly press switch S2 to increase the LED
brightness.
15) Press switch S1 to run the LED demo.
16) Press switch S4 to turn on the audio amp to the min-
imum volume.
17) Repeatedly press switch S4 to increase the volume
in 3dB steps.
MAX8678 Evaluation Kit
2 _______________________________________________________________________________________
Component Suppliers
Note: Indicate that you are using the MAX8678 when
contacting these component suppliers.
SUPPLIER PH O N E WEBSITE
Kamaya, Inc. 260- 489- 1533 www.kamaya.com
M ur ata E l ectr oni cs
N or th Am er i ca, Inc. 814- 237- 1431 www.murata-northamer ica.com
Nichia Corp. 248- 352- 6575 www.nichia.com
Panasonic Corp. 800- 405- 0652 www.panasonic.com
TDK Corp. 847- 803- 6100 www.component.tdk.com
Vishay 402- 563- 6866 www.vishay.com
Table 1. Jumper Positions
POSITIONS
JUMPER OPEN 1-2 2-3
JU1 — Differential audio input Single-ended audio input
JU2 IN- input filter capacitor is used IN- input filter capacitor is not used —
JU3 IN+ input filter capacitor is used IN+ input filter capacitor is not used —
JU4 An external pulse generator
controls the dimming
The on-board pulse generator
controls the dimming —
JU5 An external pulse generator
controls the amplifier gain
The on-board pulse generator
controls the gain —
JU6 JU6 connects the input supply to the LEDs
JU7 The pulse generator is not powered The p ul se g ener ator i s p ow er ed fr om IN 1The p ul se g ener ator i s p ow er ed fr om IN 2
Detailed Description
On-Board Pulse Generator
The on-board pulse generator provides an easy way to
evaluate the LED dimming and amplifier gain adjust-
ment. The pulse generator outputs the serial-pulse sig-
nals for ENLED and ENAMP. LED D6 indicates when
the LED driver is active and LED D5 indicates when the
audio amplifier is active. Five pushbutton switches
(S1–S5) are used to set the LED brightness and amplifi-
er gain, as shown in Table 2.
The pulse generator is powered from either IN1 or IN2.
To power from IN1, connect pins 1-2 of JU7. This pow-
ers the EV kit from the same supply as the MAX8678,
allowing the EV kit to operate from a single supply. To
power the pulse generator from a separate supply, con-
nect pins 2-3 of JU7 and connect the supply from IN2
to GND2. This is useful when evaluating the quiescent
current of the MAX8678.
Using External Pulse Generators
To use external pulse generators to control ENLED and
ENAMP, disconnect ENLED and ENAMP from the on-
board pulse generator by removing the shunts from
JU4 and JU5. Remove the shunt from JU7 to discon-
nect power from the on-board pulse generator. The sig-
nals from the external pulse generators are connected
to the pads labeled ENLED and ENAMP. For informa-
tion on the required serial-pulse signal, refer to the
MAX8678 IC data sheet.
LED Driver
Using the on-board pulse generator, press S2 to
increase LED brightness or press S3 to decrease bright-
ness. There are 31 brightness settings and an off setting.
Refer to the MAX8678 IC data sheet for details. Pressing
S1 starts the LED demo, which cycles through a preset
sequence of dimming and flashing. Press S2 or S3 to
cancel the demo. The power-up default setting is off.
Note that the LEDs might flash briefly when power is first
applied, due to the pulse-generator circuit powering up.
Evaluating with Fewer than Four LEDs
To use fewer than four LEDs, connect the square pad
next to any unused LEDs to the IN1 pad.
Using External LEDs
To connect external LEDs to the MAX8678 EV kit, cut the
trace shorting JU6. Connect the anodes of all the external
LEDs to the IN1 pad. Connect each cathode to one of the
LED outputs (square pads next to D1–D4). If fewer than four
LEDs are used, connect any unused LED output to IN1.
Audio Amplifier
Using the on-board pulse generator, press S4 to
increase the amplifier gain or S5 to reduce the gain. The
gain up/down buttons cycle through off and -9dB to
+18dB in 3dB steps. The power-up default setting is off.
Input Filter Capacitors
The EV kit has 1µF input filter capacitors installed. To
evaluate without the filter capacitors, short the pins of
JU2 and JU3. If the input bias voltage is out of the
MAX8678’s common-mode input-voltage range, these
jumpers must be open.
Differential or Single-Ended Input
JU1 selects between differential or single-ended inputs.
For a differential input, connect the input to the IN+ and
IN- pads. For a single-ended input, connect the input to
IN+ with the signal ground connected to GND1. When
using a single-ended input, the input filter capacitors
must be used (JU2 and JU3 are open).
Speaker Output
The MAX8678 EV kit is capable of driving a speaker
with 4Ωor greater impedance. Connect the speaker
across the OUT+ and OUT- pads.
Evaluates: MAX8678
MAX8678 Evaluation Kit
_______________________________________________________________________________________ 3
Table 2. Pulse-Generator Controls
PUSHBUTTON FUNCTION
S1 Used to activate the LED demo. The MAX8678 EV kit changes the brightness of LED1–LED4 in a predefined
sequence. Press S2 or S3 to stop the demo.
S2 Used to increase the brightness of LED1–LED4. When maximum brightness is reached, an additional press of S2
forces the MAX8678 to enter power-down mode for the LEDs.
S3 Used to decrease the brightness of LED1–LED4. When minimum brightness is reached, an additional press of S3
turns off the MAX8678 LEDs. Pressing S3 when the LEDs are off turns the LEDs on at full brightness.
S4 Used to increase gain of the audio amplifier. When maximum gain is reached, an additional press of S4 turns off
the audio amplifier. Pressing S4 when the audio amplifier is off turns the amplifier on at minimum gain.
S5 Used to decrease gain of the audio amplifier. When minimum gain is reached, an additional press of S3 turns off
the audio amplifier. Pressing S5 when the audio amplifier is off turns the amplifier on at maximum gain.
Evaluates: MAX8678
MAX8678 Evaluation Kit
4 _______________________________________________________________________________________
MAX8678
U1
IN1
IN
JU6
C4
1μF
C6
4.7μF
JU4
R1
470kΩ
C+
15
C-
14
IN
1
NEG
D1
TP1
C5
1μF
C3
0.1μF
NEG 13
LED1 9
OUT+
OUT+ 6
OUT+
OUT- 7
GND1
GND
2
ENLED
ENLED
ENLED
16
JU5 R2
470kΩ
ENAMP
ENAMP
ENAMP
5
JU3
C2
1μF
IN+
A+
3
JU2
JU1
EP
NEG
123
C1
1μF
A-
4
IN-
NEG
D2
TP2
LED2 10
D3
TP3
LED3 11
D4
TP4
LED4 12
BIAS 8
Figure 1. MAX8678 EV Kit Schematic (MAX8678)
Evaluates: MAX8678
MAX8678 Evaluation Kit
_______________________________________________________________________________________ 5
MAXQ2000
U2
1
2
3
VIO_2V5
27 54 55 56 49
C7
0.1μF
C8
0.1μF
IN
IN2 IN2
JU7 VIO_2V5
15
IN OUT
2GND
3SHDN
C13
1μF
C12
1μF
R5
10kΩ
GND2
GND
42
GND
28
EP
S1
18
VDDIO
SEG28/P3.4/INT4
VLCD VLCD1 VLCD2 VDD
57
VADJ
7
SEG17/P2.1 ENAMP
8
SEG18/P2.2 ENLED
9
SEG19/P2.3
36
P5.2/RX1/INT10 37
P5.3/TX1/INT11 47
P6.4/TOB/WKOUT0 48
P6.5/TO/WKOUT1 52
P7.0/TXO/INT14 53
P7.1/RX0/INT15
43
P6.0/T1B/INT12 44
P6.1/T1/INT13 63
SEG5/P0.5/INT1 58
SEG0/P0.0 59
SEG1/P0.1
45
P6.2/T2B/OW_OUT 46
P6.3/T2/OW_IN
38
P5.4/SS 39
P5.5/MOSI 40
P5.6/SCLK 41
P5.7/MISO
10
SEG20/P2.4 11
SEG21/P2.5 12
SEG22/P2.6 13
SEG23/P2.7 14
SEG24/P3.0 15
SEG25/P3.1 16
SEG26/P3.2 17
SEG27/P3.3 22
SEG32 23
SEG33/COM3 24
SEG34/COM2 25
SEG35/COM1 26
COM0
S2
19 SEG29/P3.5/INT5
S3
20 SEG30/P3.6/INT6
S4
21 SEG31/P3.7/INT7
S5
R3
220Ω
D5
62 SEG4/P0.4/INT0
DEMO
UPLED
DOWN
UP
DOWN
64 SEG6/P0.6/INT2
65 SEG7/P0.7/INT3
60 SEG2/P0.2
66 SEG8/P1.0
67 SEG9/P1.1
68 SEG10/P1.2
1SEG11/P1.3
2SEG12/P1.4
3SEG13/P1.5
4SEG14/P1.6
5SEG15/P1.7
6SEG16/P2.0
51 HFXIN
50 HFXOUT
GAIN
GAIN
VIO_2V5
LED
R4
220Ω
C11
10pF
C9
10pF
Y1
16MHz
34 32KIN
35 32KOUT
Y2
32.768kHz
29 P4.0/TCK/INT8
30 P4.1/TDI/INT9
31 P4.2/TMS
32 P4.3/TDO
33 RESET
D6 61 SEG3/P0.3
J1
JTAG
J1-2
J1-10
J1-8
J1-4 VIO_2V5
J1-7
J1-1
J1-9
J1-5
J1-3
J1-6
TCK
TDI
TMS
TDO
RESET
4
N.C.
MAX8511
U3
Figure 2. MAX8678 EV Kit Schematic (Pulse Generator)
Evaluates: MAX8678
MAX8678 Evaluation Kit
6 _______________________________________________________________________________________
Figure 3. MAX8678 EV Kit Component Placement Guide—Component Side
Evaluates: MAX8678
MAX8678 Evaluation Kit
_______________________________________________________________________________________ 7
Figure 4. MAX8678 EV Kit PCB Layout—Component Side
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8
_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Evaluates: MAX8678
MAX8678 Evaluation Kit
Figure 5. MAX8678 EV Kit PCB Layout—Solder Side
