Maxim MAX8821ETI+, MAX8821 Datasheet

General Description

The MAX8821 integrates a charge pump for white
LEDs, an audio loudspeaker amplifier, and two low­noise LDOs controlled by an I

2

C control interface. The
high-efficiency, adaptive-mode inverting charge pump
drives up to six LEDs with constant current for uniform
brightness. The LED current is controlled by an I

2

C
interface and adjusts from 0.1mA to 25.6mA per LED
into 32 pseudo-logarithmic steps. Independent volt­ages for each LED maximize efficiency even with large
LED forward voltage (V

F

) mismatch. An internal temper­ature derating function reduces the current above
+40°C to protect the LEDs.

The high-efficiency mono Class D audio amplifier deliv­ers up to 2W into a 4Ω speaker from a 5V input supply.
The amplifier features proprietary filterless Active
Emissions Limiting (AEL) technology. AEL prevents
high-frequency emissions resulting from conventional
Class D free-wheeling behavior in the presence of an
inductive load. The amplifier offers two modulation
schemes: a fixed-frequency mode (FFM) and a spread­spectrum mode (SSM) that reduce EMI-radiated emis­sions due to the modulation frequency. The amplifier
also has robust output protection and high power-sup­ply rejection ratio (PSRR). Click-and-pop suppression is
active during power-up/down, enable/disable, and for
all mode changes. The amplifier’s gain is adjustable
through an I2C interface, from -3dB to +24dB in 10 3dB
steps. Differential inputs improve common-mode noise
rejection.

The LDOs in the MAX8821 are designed for low-noise
operation. Each LDO output voltage can be individually
programmed by the I

2

C interface. Both LDO1 and

LDO2 have a high 70dB PSRR rating.

The MAX8821 includes soft-start, thermal shutdown,
open-circuit, and short-circuit protections, and is avail­able in a compact 28-pin, Thin QFN, 4mm x 4mm pack­age (0.8mm max height).

Applications

Cell Phones and Smartphones

PDAs, Digital Cameras, Camcorders

MP3 Players, GPS Devices

Features

♦ White LED Inverting Charge Pump

Independent Adaptive Current Regulators for

Each LED
6 Low-Dropout Current Regulators
Flexible I2C Dimming Control for Each LED
Ramp-Up/Down, Current Control for Each LED
Low 70µA (typ) Quiescent Current
TADerating Function Protects LEDs

♦ Mono 2W Class D Loudspeaker Amplifier

85% Efficiency (RL= 8Ω, P

OUT

= 600mW)
Low 0.05% THD+N at 1kHz
High 65dB PSRR at 1kHz
Fully Differential Inputs

-3dB to +24dB Gain Settings in 3dB Steps
Integrated Click-and-Pop Suppression
Low Quiescent Current

♦ Dual Low-Noise LDO

45µV

RMS

Output Noise, 70dB PSRR
Flexible I2C-Controlled Output Voltages
200mA and 300mA Output Current Drive

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

________________________________________________________________

Maxim Integrated Products

1

19-1014; Rev 0; 10/07

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.

Ordering Information

NEG

LED1

LED5

LED4

LED3

LED2

LED6

DUAL LOW
NOISE LDO

LOUDSPEAKER/
EARPIECE

SPK+

SPK-

INDIVIDUAL

0.1mA TO

25.6mA
DIMMING

PGND1

IN1

CMREF

IN3

REF

AGND

IN2

PGND2

AIN+

AIN-

V

DD

SDA

SCL

DIFFERENTIAL

AUDIO INPUT

LOGIC

CONTROL AND I

2

C

INTERFACE

EP

C1P C1N

C2P C2N

LDO1

LDO2

INPUT

2.7 TO 5.5V

MAX8821

Typical Operating Circuit

PART TEMP RANGE

PIN­PACKAGE

PKG

CODE

MAX8821ETI+ -40°C to +85°C

28 Thin QFN
4mm x 4mm

T2844-1

+

Denotes a lead-free package.

MAX8821

White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.

IN1, IN2, IN3, VDDto AGND..................................-0.3V to +6.0V

SCL, SDA to AGND ....................................-0.3V to (V

DD

+ 0.3V)

IN1, IN2, IN3 to NEG .............................................-0.3V to +6.0V

AGND to C2N ........................................................-0.3V to +6.0V

C1P, C2P to AGND ....................................-0.3V to (V

IN1

+ 0.3V)

LED_, C1N, C2N to NEG............................-0.3V to (V

IN1

+ 0.3V)

LDO1, LDO2, REF to AGND ......................-0.3V to (V

IN3

+ 0.3V)
CMREF, AIN+, AIN-, SPK+, SPK-

to AGND..................................................-0.3V to (V

IN2

+ 0.3V)

IN1, IN2 to IN3.......................................................-0.3V to +0.3V

PGND1, PGND2 to AGND.....................................-0.3V to +0.3V

SPK+, SPK- Short Circuit to PGND2 or IN2 ...............Continuous

Continuous Power Dissipation (T

A

= +70°C)
28-Pin, Thin QFN 4mm x 4mm

(derate 28.6mW/°C above +70°C)..............................2286mW

Junction Temperature......................................................+150°C

Storage Temperature Range .............................-65°C to +150°C

Lead Temperature (soldering, 10s) .................................+300°C

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

IN1

, V

IN2

, V

IN3

Operating

Voltage

2.7 5.5 V

VDD Operating Range 1.5 5.5 V

Undervoltage Lockout (UVLO)
Threshold

V

IN3

rising 2.25 2.45 2.65 V

UVLO Hysteresis 100 mV

VDD Shutdown Threshold 0.450 0.865 1.350 V

TA = +25°C 0.1 1

VDD = AGND

T

A

= +85°C 0.1

TA = +25°C 2 10

IN1, IN2, IN3 Shutdown Supply
Current
(All Outputs Off)

V

DD

= 3.6V

T

A

= +85°C 2

µA

Charge pump inactive, 2 LEDs at 0.1mA setting, audio
amplifier disabled, LDO1 and LDO2 disabled

70 120

LED driver disabled, audio amplifier disabled, and LDO1
and LDO2 enabled

170 250

µA

Charge pump active, 1MHz switching, all LEDs at

25.6mA setting, audio amplifier disabled, LDO1 and
LDO2 disabled

1.50 4.00

No-Load Supply Current

LED driver disabled, audio amplifier enabled, LDO1 and
LDO2 disabled

6.6 20

mA

Thermal Shutdown +160 °C

Thermal-Shutdown Hysteresis 20 °C

CHARGE PUMP

SYNC = 0 1000

SYNC = 1, SW_MODE = 00 450 550 650

SYNC = 1, SW_MODE = 01 575 700 825

Switching Frequency
(f

SW

)

SYNC = 1, SW_MODE = 10

625

± 25

kHz

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

_______________________________________________________________________________________ 3

PARAMETER CONDITIONS MIN TYP MAX UNITS

Soft-Start Time 0.1 ms

Regulation Voltage (V

IN1

- V

NEG

)5V

Open-Loop NEG Output
Resistance

(0.5 x V

IN1

- V

NEG

) / I

NEG

1.75 3.5 Ω

Output Current V

IN1

= 3.2V, LED V

FMAX

= 3.9V 154 mA

NEG Discharge Resistance in
Shutdown

All LEDs disabled 10 kΩ

LED_ CURRENT REGULATORS

Current Setting Range I

LED

_ 0.1 25.6 mA

TA = +25°C -2 ±1 +2

25.6mA setting

T

A

= -40°C to derating
function start temperature
(enabled by I

2

C)

-5 +5

Current Accuracy

0.1mA setting, T

A

= +25°C -30 ±5 +30

%

Current-Derating-Function Start
Temperature

+40 °C

Current-Derating-Function Slope TA = +40°C to +85°C -1.67 %/°C

Charge pump inactive 2.3 4.6

R

DS ON

Charge pump active 5 14

Ω

Charge pump inactive 72 120

Dropout Voltage 25.6mA setting (Note 2)

Charge pump active 120 360

mV

Current Regulator
Switchover Threshold

Charge pump inactive to active,
V

LED_

falling

125 150 175 mV

Current Regulator
Switchover Hysteresis

100 mV

TA = +25°C 0.01 1

Leakage Current in Shutdown

All LEDs
disabled

T

A

= +85°C 0.1

µA

00 524

01 1048

10 2097

Off Blink Time

B7, B6 or B3, B2,
SYNC = 0,
Table 11

11 4194

ms

00 66

01 131

10 262

On Blink Time

B5, B4 or B1, B0,
SYNC = 0,
Table 11

11 524

ms

00 262

01 524

10 1048

Ramp-Up/Down Time

LED__RU: B7, B6 or B3, B2
LED__RD: B5, B4 or B1, B0
SYNC = 0,
Tables 8, 9, 10 (Note 3)

11 2097

ms

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

MAX8821

White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO

4 _______________________________________________________________________________________

PARAMETER CONDITIONS MIN TYP MAX UNITS

AUDIO AMPLIFIER

Common-Mode Bias Voltage

0.95 x

(V

IN3

/ 2)

V

IN3

/ 2

1.05 x

(V

IN3

/ 2)

V

Output Offset Voltage V

AIN+

= V

AIN-

= V

IN3

/ 2, audio gain = 0dB ±1 mV

Common-Mode Input Voltage 0.5

V

IN3

-

1.2V

V

-3

0

3

6

9

12

15

18

21

Audio Gain Table 15, B3:B0

24

dB

Audio Gain Accuracy -3 +3 %

Audio gain = -3dB 54.4 99.0 143.5

Audio gain = 0dB 49.1 89.2 129.3

Audio gain = 3dB 43.1 78.4 113.7

Audio gain = 6dB 36.8 66.9 97.0

Audio gain = 9dB 30.5 55.5 80.5

Audio gain = 12dB 24.6 44.7 64.8

Audio gain = 15dB 19.3 35.2 51.0

Audio gain = 18dB 14.8 26.9 39.0

Audio gain = 21dB 11.1 20.2 29.3

Input Resistance

Audio gain = 24dB 8.2 15.0 22.0

kΩ

V

IN2

= V

IN3

= 3.6V 46

Common-Mode Rejection Ratio

f = 1kHz, V

IN2

= V

IN3

= 3.6V 46

dB

f = 217Hz 65

Power-Supply Rejection Ratio

V

AIN+

= V

AIN-

= V

IN3

/ 2,

100mV

P-P

at V

IN3 f = 20kHz 50

dB

RL = 8Ω 0.36 0.5

V

IN3

= 3.6V

R

L

= 4Ω 0.85

RL = 8Ω 0.8 1.1

Output Power

THD+N = 1%,
f = 1kHz
(Note 4)

V

IN3

= 5V

R

L

= 4Ω 2.0

W

Total Harmonic Distortion Plus
Noise

RL = 8Ω, f = 1kHz, P

OUT

= 0.25W,

V

IN2

= V

IN3

= 3.6V

0.05 %

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

MAX8821

PARAMETER CONDITIONS MIN TYP MAX UNITS

Fixed-frequency mode (FFM) 91

Spread-spectrum mode (SSM) 89

FFM A weighted 93

Signal-to-Noise Ratio

R

L

= 8Ω, f = 1kHz,

P

OUT

= 0.25W,

V

IN2

= V

IN3

= 3.6V

SSM A weighted 91

dB

SW_MODE = 00 900 1100 1300

SW_MODE = 01 1150 1400 1650

Oscillator Frequency
(f

osc

)

SW_MODE = 10

1250

±50

kHz

Differential Input
Resistance

Shutdown mode only 100 kΩ

Output Current Limit SPK+, SPK- short circuited to PGND2 or to IN2 2 A

Wake-Up Delay After
Short Circuit

110 µs

LDO1

Output Voltage V

LDO1

3.6V ≤ V

IN3

≤ 5.5V,

1mA ≤ I

LDO1

≤ 300mA

1.164 1.200

1.236 V

Maximum Output
Current

300 mA

Output Current Limit V

LDO1

= 0V 400 650 1000 mA

Dropout Voltage I

LDO1

= 200mA, T

A

= +25°C (Note 5) 150 300 mV

Line Regulation

V

IN3

stepped from 3.4V to 5.5V,

I

LDO1

= 150mA

2.4 mV

Load Regulation I

LDO1

stepped from 1mA to 300mA 25 mV

Power-Supply
Rejection
ΔV

IN3

/ΔV

LDO1

10Hz to 10kHz,
I

LDO1

= 30mA

70 dB

Output Voltage Noise
(RMS)

100Hz to 100kHz,
I

LDO1

= 30mA

45 µV

RMS

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

_______________________________________________________________________________________ 5

MAX8821

White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO

6 _______________________________________________________________________________________

PARAMETER CONDITIONS MIN TYP MAX UNITS

0000 1.164 1.2 1.236

0001 1.261 1.3 1.339

0010 1.455 1.5 1.545

0011 1.552 1.6 1.648

0100 1.746 1.8 1.854

0101 1.843 1.9 1.957

0110 1.940 2.0 2.060

0111 2.231 2.3 2.369

1000 2.425 2.5 2.575

1001 2.522 2.6 2.678

1010 2.619 2.7 2.781

1011 2.716 2.8 2.884

1100 2.813 2.9 2.987

1101 2.910 3.0 3.090

1110 3.007 3.1 3.193

Programmable Output
Voltage

I

LDO1

= 50mA
control bits B3:B0;
see Table 13

1111 3.104 3.2 3.296

V

Shutdown Output
Impedance

LDO1 disabled through I

2

C1kΩ

LDO2

Output Voltage V

LDO2

3.6V ≤ V

IN3

≤ 5.5V,

1mA ≤ I

LDO2

≤ 200mA

1.455 1.500

1.545 V

Maximum Output
Current

200 mA

Output Current Limit V

LDO2

= 0V 250 550 750 mA

Dropout Voltage I

LDO2

= 133mA, T

A

= +25°C (Note 5) 100 200 mV

Line Regulation V

IN3

stepped from 3.4V to 5.5V, I

LDO2

= 100mA 2.4 mV

Load Regulation I

LDO2

stepped from 1mA to 200mA 25 mV

Power-Supply
Rejection
ΔV

IN3

/ΔV

LDO2

10Hz to10kHz,
I

LDO2

= 20mA

70 dB

Output Voltage Noise
(RMS)

100Hz to100kHz,
I

LDO2

= 20mA

45 µV

RMS

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

_______________________________________________________________________________________ 7

PARAMETER CONDITIONS MIN TYP MAX UNITS

0000 1.455 1.5 1.545

0001 1.552 1.6 1.648

0010 1.746 1.8 1.854

0011 1.940 2.0 2.060

0100 2.134 2.2 2.266

0101 2.231 2.3 2.369

0110 2.328 2.4 2.472

0111 2.425 2.5 2.575

1000 2.522 2.6 2.678

1001 2.619 2.7 2.781

1010 2.716 2.8 2.884

1011 2.813 2.9 2.987

1100 2.910 3.0 3.090

1101 3.007 3.1 3.193

1110 3.104 3.2 3.296

Programmable Output
Voltage

I

LDO2

= 50mA
control bits
B3:B0;
see Table 14

1111 3.201 3.3 3.399

V

Shutdown Output
Impedance

LDO2 disabled through I

2

C1kΩ

I2C INTERFACE (Figure 8)

Logic Input High
Voltage

0.7 x
V

DD

V

Logic Input Low
Voltage

0.3 x
V

DD

V

TA = +25°C -1 0.01 +1

Logic Input Current VIL = 0V or VIH = V

DD

TA = +85°C 0.1

µA

SDA Output Low
Voltage

I

SDA

= 3mA 0.03 0.4 V

I2C Clock Frequency 400 kHz

Bus-Free Time
Between START and
STOP

t

BUF

1.3 µs

Hold Time Repeated
START Condition

t

HD_STA

0.6 0.1 µs

SCL Low Period t

LOW

1.3 0.2 µs

SCL High Period t

HIGH

0.6 0.2 µs

Setup Time Repeated
START Condition

t

SU_STA

0.6 0.1 µs

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

MAX8821

White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO

8 _______________________________________________________________________________________

Typical Operating Characteristics

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= +25°C, unless otherwise noted.)

PARAMETER CONDITIONS MIN TYP MAX UNITS

SDA Hold Time t

HD_DAT

0 -0.01 µs

SDA Setup Time t

SU_DAT

100 50 ns

Setup Time for STOP
Condition

t

SU_STO

0.6 0.1 µs

ELECTRICAL CHARACTERISTICS (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted.

Typical values are at T

A

= +25°C.) (Note 1)

Note 1: Limits are 100% production tested at T

A

= +25°C. Limits over the operating temperature range are guaranteed by design.

Note 2: Dropout voltage is defined as the LED_ to GND voltage when the current into LED_ drops 10% from the value at V

LED_

= 0.5V.

Note 3: Ramp-up time is from 0mA to full scale; ramp-down time is from full scale to 0mA.
Note 4: Output power is specified by a combination of a functional output current test and characterization analysis.
Note 5: The dropout voltage is defined as V

IN_

- V

OUT

when V

OUT

is 100mV below the nominal value of V

OUT

. The specification only

applies when V

OUT

≥ 3.0V.

LED CHARGE PUMP

0

30

20

10

40

50

60

70

80

90

100

2.7 3.33.0 3.6 3.9 4.2

EFFICIENCY vs. SUPPLY VOLTAGE

(DRIVING SIX LEDS)

MAX8821 toc01

SUPPLY VOLTAGE (V)

EFFICIENCY (%)

1.6mA/LED

6.4mA/LED

20.8mA/LED

16mA/LED

LEDs HAVE MATCHED V

F

0

30

20

10

40

50

60

70

80

90

100

2.7 3.33.0 3.6 3.9 4.2

EFFICIENCY vs. SUPPLY VOLTAGE

(DRIVING SIX LEDS)

MAX8821 toc02

SUPPLY VOLTAGE (V)

EFFICIENCY (%)

1.6mA/LED

6.4mA/LED

20.8mA/LED

16mA/LED

LEDs HAVE MISMATCHED V

F

20.8mA/LED

40

60

50

80

70

90

100

4.2 3.7 3.63.9 3.8 3.5 3.4 3.0

EFFICIENCY vs. Li+ BATTERY VOLTAGE

DRIVING SIX LEDs

MAX8821 toc03

Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)

EFFICIENCY P

LED

/P

BATT

(%)

20.8mA/LED

16mA/LED

6.4mA/LED

1.6mA/LED

20.8mA/LEDLEDs HAVE HIGH MATCHED V

F

0

75

50

25

100

125

150

175

200

225

250

2.7 3.2

3.7

4.2

SUPPLY CURRENT

vs. SUPPLY VOLTAGE (DRIVING SIX LEDs)

MAX8821 toc04

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

I

LED

= 20.8mA

I

LED

= 16mA

I

LED

= 6.4mA

I

LED

= 1.6mA

LEDs HAVE HIGH MISMATCHED V

F

SUPPLY CURRENT

vs. SUPPLY VOLTAGE (RGB MODULE)

MAX8821 toc05

SUPPLY VOLTAGE (V)

SUPPLY CURRENT (mA)

3.73.2

10

20

30

40

50

60

70

0

2.7 4.2

I

LED

= 20.8mA

I

LED

= 16mA

I

LED

= 6.4mA

I

LED

= 1.6mA

RGB MODULE: LUMEX SML-LX3632SISUGSBC

LED CURRENT MATCHING

vs. SUPPLY VOLTAGE (16mA/LED)

MAX8821 toc06

SUPPLY VOLTAGE (V)

LED CURRENT (mA)

5.14.73.9 4.33.53.1

15.6

15.7

15.8

15.9

16.0

16.1

16.2

16.3

16.4

16.5

15.5

2.7 5.5

CHARGE PUMP IN 1.5x

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

_______________________________________________________________________________________

9

Typical Operating Characteristics (continued)

(V

IN1

= V

IN2

= V

IN3

= VDD= 3.6V, V

AGND

= V

PGND1

= V

PGND2

= 0V, circuit of Figure 2, TA= +25°C, unless otherwise noted.)

LED CURRENT vs. AMBIENT

TEMPERATURE

MAX8821 toc07

TEMPERATURE (°C)

LED CURRENT (mA)

806040200-20

5

10

15

20

25

30

0

-40 100

CURRENT DERATING ENABLED

400ns/div

1x MODE OPERATING

WAVEFORMS (V

IN

= 4V)

V

IN

V

NEG

200mA/div

AC-COUPLED
100mV/div

MAX8821 toc08

I

IN

I

LED

ALL LEDs ON, I

LED

= 25.6mA

2V/div
0V

0A
20mA/div

0A

400ns/div

1.5x MODE OPERATING
WAVEFORMS (V

IN

= 3V)

V

IN

V

NEG

200mA/div

AC-COUPLED
100mV/div

MAX8821 toc09

I

IN

I

LED

ALL LEDs ON, I

LED

= 25.6mA

2V/div

0A
20mA/div

0A

0V

1ms/div

LED LINE TRANSIENT WITH MODE CHANGE

(V

IN

= 3.8V TO 3.4V TO 3.8V)

V

IN

200mA/div

3.8V

MAX8821 toc10

I

IN

I

LED6

ALL LEDs AT 25.6mA SETTING

0A

20mA/div

0A

3.4V

1ms/div

LED LINE TRANSIENT WITH MODE CHANGE

(V

IN

= 4.2V TO 3.8V TO 4.2V)

V

IN

200mA/div

4.2V

MAX8821 toc11

I

IN

I

LED6

ALL LEDs AT 25.6mA SETTING

0A

20mA/div

0A

3.8V

1ms/div

LED STARTUP WAVEFORMS

(V

IN

= 4V)

V

IN

50mA/div

AC-COUPLED
50mV/div

MAX8821 toc12

I

IN

I

LED6

0A

20mA/div

0A

1ms/div

LED SHUTDOWN WAVEFORMS

(V

IN

= 4V)

V

IN

50mA/div

AC-COUPLED

MAX8821 toc13

I

IN

I

LED6

0A

20mA/div

0A

50mV/div

400ms/div

LED RAMP-UP

10mA/div

MAX8821 toc14

I

LED6

I

LED5

0A

0A

10mA/div