19-3114; Rev 0; 12/07
MAX8822 Evaluation Kit
General Description
The MAX8822 evaluation kit (EV kit) is a fully assem-
bled and tested printed-circuit board (PCB) that
demonstrates the MAX8822 ultra-efficient negative
charge-pump LED driver with dual LDOs. The
MAX8822 drives up to four white LEDs (WLEDs) for
backlighting and contains two 200mA, low-noise, high
power-supply-rejection-ratio (PSRR) LDOs to power
external camera modules or other loads. The EV kit
includes a MAXQ2000 microcontroller circuit that pro-
vides the serial-pulse control necessary to adjust
WLED brightness and LDO output voltages. Through
the MAXQ2000, WLED brightness levels are sequen-
tially incremented/decremented between 0.1mA and
24mA and shut down by pushbutton controls. Sixteen
different LDO output-voltage combinations (from off to
3.3V) are selected by DIP-switch positions and
latched by a pushbutton. The MAX8822 IC includes
soft-start, WLED and LDO short-circuit protection, and
thermal shutdown.
Features
o
Powers Up to 4 White LEDs
Independent Adaptive Voltage Supply for Each
LED
24mA to 0.1mA Dimming Range
1% (typ) Current Accuracy and 0.3% (typ)
Current Matching
o
Dual 200mA Low-Noise, High PSRR LDOs
16 Selectable LDO Output Voltage
Combinations from OFF Up to 3.3V
o
MAXQ2000 Microprocessor Circuit for LED and
LDO Serial-Pulse Control
Sequential UP/DOWN LED Dimming
Pushbutton Control
DIP-Selectable LDO Output Voltages
o
2.7V to 5.5V Input Range
o
Selectable Microprocessor Circuit Power Input
(IN1, IN2)
o
WLED and LDO Short-Circuit and Thermal
Protection
o
Small, Low-Profile Components
o
Lead-Free and RoHS-Compliant
o
Fully Assembled and Tested
Evaluates: MAX8822
Ordering Information
PART
MAX8822EVKIT+
TYPE
EV Kit
+Denotes
lead-free and RoHS-compliant.
Component List
DESIGNATION
C1
QTY
1
DESCRIPTION
4.7µF ±10%, 6.3V X5R ceramic
capacitor (0603)
TDK C1608X5R0J475K or equivalent
0.1µF ±10%, 10V X5R ceramic
capacitors (0402)
TDK C1005X5R1A104K or equivalent
1µF ±10%, 6.3V X5R ceramic
capacitors (0402)
TDK C1005X5R0J105K
Murata GRM155R60J105K or
equivalent
2.2µF ±10%, 6.3V X5R ceramic
capacitor (0603)
TDK C1608X5R0J225K
Murata GRM185R60J225K or
equivalent
DESIGNATION
QTY
DESCRIPTION
10pF ±0.5pF, 50V C0G ceramic
capacitors (0402)
TDK C1005C0G1H100D or
equivalent
White LEDs
Green LEDs
Not installed, 10-pin (2 x 5) header,
0.1in spacing
Sullins PEC36DAAN (72-pin strip, cut
to size as needed)
Digi-Key S2012E-36-ND
2-pin headers
Sullins PEC36SAAN (36-pin strip, cut
to size as needed)
Digi-Key S1012E-02-ND
C9, C11
2
C2, C8, C10
3
D1–D4
D5, D6, D7
4
3
C3, C4, C6, C7,
C12, C13
6
J1
0
C5
1
JU1, JU2
2
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX8822 Evaluation Kit
Evaluates: MAX8822
Component List (continued)
DESIGNATION
QTY
DESCRIPTION
3-pin header
Sullins PEC36SAAN (36-pin strip, cut
to size as needed)
Digi-Key S1012E-02-ND
Not installed, PCB
connection—shorted (0402)
200kΩ ±5% resistors (0402),
lead free
220Ω ±5% resistors (0402), lead free
Momentary pushbutton switches
Panasonic EVQ-PHP03T
4-position DIP switch
CTS 206-4 or equivalent
Not installed, test points
Y1
Y2
—
—
1
0
3
1
U3
1
U2
1
DESIGNATION
QTY
DESCRIPTION
Ultra-efficient negative charge-pump
LED driver with dual LDOs
(16-pin thin QFN-EP, 3mm x 3mm)
Maxim MAX8822ETE+
(Top Mark: AFW)
Low-power LCD microcontroller
(68-pin QFN, 10mm x 10mm)
Maxim MAXQ2000-RAX+
Ultra-low-noise, high PSRR, LDO
linear regulator
(5-pin SC70)
Maxim MAX8511EXK25+
20MHz crystal
Vishay XT9S20ANA20M, lead free
Citizen HC49US20.000MABJ-U
Not installed, crystal (1206)
Shunts, 2 position
PCB: MAX8822 Evaluation Kit+
JU3
1
U1
1
JU4–JU8
R1, R2
R3, R4, R5
S1, S2, S3
S4
TP1–TP4
0
2
3
3
1
0
Component Suppliers
SUPPLIER
Citizen America Corp.
CTS Corp.
Digi-Key Corp.
Murata Mfg. Co., Ltd.
Nichia Corp.
Panasonic Corp.
Sullins Electronics
TDK Corp.
Vishay
PHONE
310-781-1460
818-842-7277
800-344-4539
770-436-1300
248-349-9800
714-373-7939
760-744-0125
847-803-6100
402-563-6866
WEBSITE
www.citizencrystal.com
www.ctscorp.com
www.digikey.com
www.murata.com
www.nichia.com
www.panasonic.com
www.sullinselectronics.com
www.component.tdk.com
www.vishay.com
Note:
Indicate that you are using the MAX8822 when contacting these component suppliers.
Quick Start
Required Equipment
Before beginning, the following equipment is needed:
• One variable-voltage DC power supply capable of
supplying 2.7V to 5.5V at 1A
• Two digital voltmeters (DVMs)
• Two 200mA dummy loads
• One DVM to evaluate the inverting charge-pump
turn-on (optional)
Procedure
The MAX8822 EV kit is fully assembled and tested.
Follow the steps below to verify operation of the
MAX8822 EV kit circuit (see Figure 1).
Caution: Do
not turn on the power supply until all connections
are completed.
1) Ensure that a shunt is installed on jumpers JU1 and
JU2 located on the EV kit.
2) Ensure that a shunt is installed between pins 1-2 of
jumper JU3 located on the EV kit.
3) Turn the power supply on and preset to 4.2V.
4) Turn off the power supply.
Do not turn on the power
supply until all connections are completed.
2
_______________________________________________________________________________________
MAX8822 Evaluation Kit
5) Configure connections according to Figure 1.
a) Connect the positive terminal of the power sup-
ply to the IN1 pad located on the EV kit.
Connect the negative terminal of the power
supply to a GND pad located on the EV kit.
b) Connect the positive terminal of a DVM to the
LDO1 pad on the EV kit. Connect the ground
terminal of that DVM to a GND pad located on
the EV kit. This is the LDO1 DVM.
c) Connect the positive terminal of the other DVM
to the LDO2 pad on the EV kit. Connect the
ground terminal of that DVM to a GND pad
located on the EV kit. This is the LDO2 DVM.
d) For optional charge-pump evaluation of step
15, connect the positive terminal of a DVM to
the NEG pad. Connect the negative terminal of
that DVM to a GND pad. This is the NEG DVM.
6) Turn on the power supply. Verify that the WLEDs
are off. Verify that the LDO1 and LDO2 DVMs indi-
cate 0V.
7) Press the UP pushbutton (S1) once. Verify that the
WLEDs are illuminated at low brightness and that the
green LED (D6) turns on indicating the WLEDs are
enabled.
8) Press S1 a few more times. WLED brightness increases
according to the dimming scheme shown in Table 1.
9) Press the DOWN pushbutton (S2). WLED bright-
ness decreases according to the dimming scheme
shown in Table 1.
10) Place the LEDs in shutdown mode by repeatedly
pressing S1 or S2 until the WLEDs turn off. Verify that
the green LED (D6) turns off.
11) Set the LDO SEL DIP switch (S4) to 0000. Press the
LDO SET button (S3). Verify that the LDO1 DVM indi-
cates approximately 2.8V and the LDO2 DVM indi-
cates approximately 1.2V. Verify that the green LEDs
(D7 and D5) turn on indicating that LDO1 and LDO2
are enabled, respectively.
12) Connect a 200mA load to LDO1. Verify that the
LDO1 DVM indicates approximately 2.8V.
13) Connect a 200mA load to LDO2. Verify that the
LDO2 DVM indicates approximately 1.2V.
14) Set DIP switch S4 to 1111. Press the LDO SET button
(S3). Verify that both LDOs turn off. Verify that the
LDO1 DVM and the LDO2 DVM indicate 0V. Verify
that the green LEDs (D7 and D5) turn off.
15) Optional: To evaluate the inverting charge-pump
turn-on, perform the following procedure:
a) Set the power supply to 4.2V.
b) Program the LEDs for full brightness by press-
ing the UP/DOWN pushbuttons.
c) Verify that the NEG voltmeter indicates 0V.
d) Reduce the power-supply voltage to 3V.
e) Verify that the NEG DVM reads a negative
voltage, indicating that the charge pump is on.
f) Increase the power-supply voltage to 4.2V.
g) Verify that the NEG DVM reads 0V, indicating
that the charge pump is now off.
Evaluates: MAX8822
POWER SUPPLY
(PS1)
-
+
LDO2 DVM
+
-
LDO1 DVM
-
+
LDO2
1
LDO
SEL
LDO
SET
UP
DOWN
0
B0
B1
B2 S4
B3
S3
S1
1
2
3
JU3
LDO1
GND
GND
IN2
IN1
MAX8822 EV KIT
-
NEG DVM
+ (OPTIONAL)
D7
D5
D6
JU1
NEG
JU2
S2
Figure 1. MAX8822 EV Kit Quick-Start Setup
_______________________________________________________________________________________
3
MAX8822 Evaluation Kit
Evaluates: MAX8822
Detailed Description
The MAX8822 evaluation kit (EV kit) is a fully assembled
and tested PCB that demonstrates the MAX8822 ultra-
efficient negative charge-pump LED driver with dual
LDOs. The MAX8822 drives up to four white LEDs
(WLEDs) for backlighting and contains two 200mA, high
power-supply-rejection-ratio (PSRR) LDOs to power
external camera modules or other loads. The EV kit
includes a MAXQ2000 microcontroller circuit that pro-
vides the serial-pulse control signals necessary to adjust
WLED brightness and LDO output voltages. Through the
MAXQ2000, WLED brightness levels are sequentially
incremented/decremented between 0.1mA and 24mA
and shut down by UP/DOWN pushbutton controls.
Sixteen different LDO output-voltage combinations (from
off to 3.3V) are selected by DIP-switch positions and
latched by a pushbutton. The EV kit includes two jumpers
(JU1, JU2) to manually place the WLED regulators and
LDOs in shutdown mode or for configuring the WLED
regulators and LDO1/LDO2 for externally supplied serial-
pulse control. The MAX8822 IC includes soft-start, WLED
and LDO short-circuit protection, and thermal shutdown.
LED Dimming Control
The MAX8822 EV kit utilizes a MAXQ2000 microcon-
troller to implement serial-pulse WLED dimming control,
programming the WLED current from 0.1mA to 24mA
and to place the LED regulators in shutdown mode.
(Refer to the
LED Dimming Control
section of the
MAX8822 IC data sheet for more details on serial-pulse
dimming control.) The microcontroller uses the UP and
DOWN pushbuttons (S1 and S2) to increment and
decrement the WLED current in a sequential manner,
according to the dimming scheme displayed in Table 1.
Upon each UP/DOWN pushbutton event, the microcon-
troller sends the required number of serial pulses to the
MAX8822 ENLED input to program the WLED current to
the desired value. WLED brightness is incremented from
0.1mA to 24mA in 31 UP button presses with shutdown
occurring on the 32nd press. WLED brightness is decre-
mented from 24mA to 0.1mA in 31 DOWN button press-
es with shutdown occurring on the 32nd press. A green
LED (D6) is illuminated when the microcontroller has
programmed the WLEDS to an on state, corresponding
to a V
ENLED
high condition.
Table 1. LED Dimming Scheme Using UP/DOWN Pushbutton Control
UP (S1)
PRESS
COUNT*
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
DOWN (S2)
PRESS
COUNT*
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
ENLED
PULSE
COUNT
0**
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PROGRAMMED
LED_ CURRENT
(mA)
Shutdown
24.0
22.4
20.8
19.2
17.6
16.0
14.4
12.8
11.2
9.6
8.0
6.4
5.6
4.8
4.0
3.2
UP (S1)
PRESS
COUNT*
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
—
DOWN (S2)
PRESS
COUNT*
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
—
ENLED
PULSE
COUNT
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
0**
—
PROGRAMMED
LED_ CURRENT
(mA)
2.8
2.4
2.0
1.6
1.4
1.2
1.0
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
Shutdown
—
*Referenced
from LED shutdown (VENLED = 0V).
**ENLED
is held low.
4
_______________________________________________________________________________________
MAX8822 Evaluation Kit
To alternatively place the WLEDs in shutdown mode,
remove the shunt from jumper JU1. This pulls ENLED to
GND, fulfilling the requirements to shut down the
MAX8822 WLED current regulators. Placing the WLEDs in
shutdown mode in this manner overrides the microcon-
troller, leaving D6 illuminated if the WLEDs were previous-
ly on. To bring the WLEDs out of manual shutdown,
replace the shunt on jumper JU1. If D6 is illuminated (indi-
cating that ENLED is high), WLED current is programmed
to 24mA. Sequential WLED pushbutton control using the
UP/DOWN pushbuttons is resumed from the last WLED
current value programmed prior to manual shutdown.
To control the WLED brightness using an external serial-
pulse signal, remove the shunt from jumper JU1. Apply the
external serial-pulse-control signal between the ENLED
pad and GND. Refer to the MAX8822 IC data sheet for
WLED dimming serial-pulse-control requirements.
switch (S4) to select the LDO1/LDO2 output voltages
according to the scheme displayed in Table 2. Once S4
is set to the desired DIP binary code (B3–B0), press the
LDO SET pushbutton (S3) to program the LDO output
voltages. Upon actuating S3, the microcontroller sends
the required number of serial pulses to the MAX8822
ENLDO input to program the LDO voltages. Green
LEDs (D5 and D7) indicate when LDO2 or LDO1 is pro-
grammed to a nonzero output voltage, respectively.
To place both LDOs in shutdown mode, remove the
shunt from jumper JU2. This pulls ENLDO to GND, ful-
filling the requirements to shut down the MAX8822
LDOs. Placing the LDOs in shutdown mode in this man-
ner overrides the microcontroller, leaving the LDO_
enabled LEDs lit according to the LDO_ status prior to
manual shutdown. To bring the LDOs out of manual
shutdown, replace the shunt on jumper JU2. If D5 or D7
is illuminated (indicating that ENLDO is high) when
replacing JU2, the LDOs are set to the OFF state. The
LDO output voltages are then programmed according
to the procedure listed above.
To control the LDO_ voltage using an external signal,
remove the shunt from jumper JU2. Apply the external
serial-pulse control signal to the ENLDO pad. Refer to
the MAX8822 IC data sheet for LDO voltage serial-
pulse control requirements.
Evaluates: MAX8822
LDO_ Voltage Control
The MAX8822 EV kit utilizes a MAXQ2000 microcon-
troller to implement serial-pulse LDO voltage control,
programming the output voltage of both LDOs in certain
combinations from OFF to 3.3V. (Refer to the
LDO1/LDO2 Output Voltage Control
section of the
MAX8822 IC data sheet for more details on LDO volt-
age control.) The microcontroller uses the LDO SEL DIP
Table 2. LDO1/LDO2 Voltage Control DIP Settings
LDO SEL DIP CODE
(B3–B0)
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
ENLDO PULSE COUNT*
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
PROGRAMMED LDO1 VOLTAGE**
2.8V
3.3V
2.8V
3.3V
1.2V
1.8V
2.8V
3.3V
2.8V
0V
0V
0V
1.8V
2.8V
3.3V
0V
PROGRAMMED LDO2 VOLTAGE**
1.2V
1.2V
1.5V
1.5V
1.8V
1.8V
1.8V
1.8V
2.8V
1.5V
1.8V
2.8V
0V
0V
0V
0V
*Referenced
from VENLDO = high.
**Upon
LDO SET (S3) button press.
_______________________________________________________________________________________
5
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