Datasheet MAX8821ETI+, MAX8821 Datasheet (Maxim)

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

MAX8821

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

10 ______________________________________________________________________________________

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.)

-140

-120

-100

-80

-60

-40

-20

0

20

0 5 10 15 20

FIXED-FREQUENCY-MODE OUTPUT

SPECTRUM vs. FREQUENCY

MAX8821 toc19

FREQUENCY (kHz)

AMPLITUDE (dBV)

RL = 8Ω
V

BATT

= 5V

V

OUT

= -60dBV
UNWEIGHTED
FFM -1100kHz

-140

-120

-100

-80

-60

-40

-20

0

20

0 5 10 15 20

SPREAD-SPECTRUM-MODE OUTPUT

SPECTRUM vs. FREQUENCY

MAX8821 toc18

FREQUENCY (kHz)

AMPLITUDE (dBV)

RL = 8Ω
V

BATT

= 5V

V

OUT

= -60dBV

UNWEIGHTED

AUDIO AMPLIFIER PHASE

vs. FREQUENCY

MAX8821 toc21

FREQUENCY (kHz)

PHASE (°)

101

-50

-40

-30

-20

-10

0

10

20

-60

0.1 100

TOTAL HARMONIC DISTORTION

PLUS NOISE vs. FREQUENCY

MAX8821 toc15

FREQUENCY (kHz)

THD+N (%)

1010.1

0.1

0.01 100

1

0.01

P

OUT

= 25mW

P

OUT

= 350mW

P

OUT

= 100mW

VIN = 3.6V
R

L

= 8

Ω

TOTAL HARMONIC DISTORTION

vs. OUTPUT POWER

MAX8821 toc16

OUTPUT POWER (W)

THD+N (%)

0.80.60.40.2

0.1

1

10

100

0.01
0 1.0

VIN = 3.6V
R

L

= 8

Ω

TOTAL HARMONIC DISTORTION

vs. OUTPUT POWER

MAX8821 toc17

OUTPUT POWER (W)

THD+N (%)

2.52.01.51.00.5

0.1

1

10

100

0.01

03.0

VIN = 5V
R

L

= 4

Ω

11.75

11.90

11.85

11.80

11.95

12.00

12.05

12.10

12.15

12.20

12.25

0 5 10 15 20

AUDIO AMPLIFIER GAIN

vs. FREQUENCY

MAX8821 toc20

FREQUENCY (kHz)

GAIN (dB)

AUDIO AMPLIFIER PSRR

vs. FREQUENCY

MAX8821 toc22

FREQUENCY (kHz)

PSRR (dB)

1

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

-100

0.1 10

V

RIPPLE

= 100mV

P-P

AUDIO GAIN = 0dB
R

L

= 4

Ω

C

CMREF

= 0.1μF

C

CMREF

= 1μF

WIDEBAND OUTPUT SPECTRUM

SPREAD-SPECTRUM MODE

MAX8821 toc23

FREQUENCY (MHz)

AMPLITUDE (dBV)

1010.10.01

-120

-100

-80

-60

-40

-20

0

-140

0.001 100

RL = 8

Ω

INPUTS AC GROUNDED

CLASS D AMP

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________

11

WIDEBAND OUTPUT SPECTRUM

FIXED-FREQUENCY MODE

MAX8821 toc24

FREQUENCY (MHz)

AMPLITUDE (dBV)

1010.10.01

-120

-100

-80

-60

-40

-20

0

-140

0.001 100

RL = 8

Ω

INPUTS AC GROUNDED

0

0.5

1.5

1.0

2.0

2.5

2.7 3.53.1 3.9 4.3 4.7 5.1 5.5

OUTPUT POWER

vs. SUPPLY VOLTAGE

MAX8821 toc25

SUPPLY VOLTAGE (V)

OUTPUT POWER (W)

THD+N = 10%

THD+N = 1%

RL = 8Ω

0

1.0

0.5

2.0

1.5

3.0

2.5

3.5

2.7 3.5 3.93.1 4.3 4.7 5.1 5.5

OUTPUT POWER

vs. SUPPLY VOLTAGE

MAX8821 toc26

SUPPLY VOLTAGE (V)

OUTPUT POWER (W)

THD+N = 10%

THD+N = 1%

RL = 4Ω

50

65

60

55

75

70

95

90

85

80

100

2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5

EFFICIENCY

vs. SUPPLY VOLTAGE

MAX8821 toc27

SUPPLY VOLTAGE (V)

EFFICIENCY (%)

RL = 8Ω

RL = 4Ω

0

30

20

10

40

50

60

70

80

90

100

0 0.5 1.0 1.5 2.0

EFFICIENCY vs. OUTPUT POWER

MAX8821 toc28

OUTPUT POWER (W)

EFFICIENCY (%)

RL = 8Ω

RL = 4Ω

VIN = 3.6V

0

30

20

10

40

50

60

70

80

90

100

01234

EFFICIENCY

vs. OUTPUT POWER

MAX8821 toc29

OUTPUT POWER (W)

EFFICIENCY (%)

RL = 8Ω

RL = 4Ω

VIN = 5V

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.)

MAX8821

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

12 ______________________________________________________________________________________

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.)

STARTUP WAVEFORMS

MAX8821 toc30

1V/div

1V/div

AIN+ - AIN-

SPK+ - SPK-

0V

0V

AV = 0dB

SHUTDOWN WAVEFORMS

MAX8821 toc31

1V/div

1V/div

AIN+ - AIN-

SPK+ - SPK-

0V

0V

AV = 0dB

0

60

40

20

80

100

120

140

160

180

200

010050 150 200 250 300

LDO DROPOUT VOLTAGE

vs. LOAD CURRENT

MAX8821 toc32

LOAD CURRENT (mA)

DROPOUT VOLTAGE (mV)

LDO1

LDO2

LDO OUTPUT VOLTAGE

ACCURACY vs. LOAD CURRENT

MAX8821 toc33

LOAD CURRENT (mA)

OUTPUT VOLTAGE ACCURACY (%)

25020015010050

-4

-3

-2

-1

0

1

-5
0300

V

LDO2

= 2.8V

V

LDO1

= 2.8V

LDO OUTPUT VOLTAGE

vs. TEMPERATURE

MAX8821 toc34

TEMPERATURE (°C)

OUTPUT VOLTAGE (V)

603510-15

2.65

2.70

2.75

2.80

2.85

2.90

2.60

-40 85

I

LDO1

= 0A

I

LDO2

= 0A

I

LDO2

= 100mA

I

LDO1

= 100mA

DUAL LDOs

LDO PSRR

vs. FREQUENCY

MAX8821 toc35

FREQUENCY (kHz)

PSRR (dB)

1010.1

-80

-70

-60

-50

-40

-30

-20

-10

0

-90

0.01 100

I

LDO2

= 20mA

I

LDO1

= 30mA

V

IN-RIPPLE

= 100mV

P-P

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________

13

10μs/div

LDO2 LOAD TRANSIENT

MAX8821 toc39

AC-COUPLED
50mV/div

V

LDO2

I

LDO2

0A

50mA/div

2ms/div

LDO SHUTDOWN RESPONSE

(LDO1, LDO2 UNLOADED)

MAX8821 toc40

V

LDO1

V

LDO2

0V

0V
1V/div

1V/div

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.)

200μs/div

LDO LINE TRANSIENT

(V

IN3

= 3.6V TO 4.5V)

MAX8821 toc37

4.5V

3.6V

AC-COUPLED
10mV/div

AC-COUPLED
10mV/div

V

IN

V

LDO1

V

LDO2

I

LDO1

= 150mA, I

LDO2

= 100mA

10μs/div

LDO1 LOAD TRANSIENT

MAX8821 toc38

AC-COUPLED
50mV/div

V

LDO1

I

LDO1

0A

50mA/div

LDO OUTPUT SPECTRUM

MAX8821 toc36

FREQUENCY (kHz)

AMPLITUDE (dBV)

100100.01 0.1 1

-140

-120

-100

-80

-60

-40

-20

0

-160

0.001 1000

MAX8821

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

14 ______________________________________________________________________________________

Pin Description

PIN NAME FUNCTION

1V

DD

I2C Input Supply Voltage. The VDD supply range is 1.5V to 5.5V. Drive VDD high to enable the I2C
control. Drive V

DD

low to place the IC into shutdown mode.

2 CMREF

Audio Common-Mode Reference Voltage. Bypass CMREF with a 0.1µF ceramic capacitor to AGND
as close as possible to the IC.

3 AIN+ Noninverting Audio Input

4 AIN- Inverting Audio Input

5 PGND2 Audio Amplifier Power Ground. Connect PGND2 to the system ground plane.

6 SPK- Audio Amplifier Negative Output

7 SPK+ Audio Amplifier Positive Output

8 IN2

Audio Amplifier Output Buffer Supply Voltage Input. The input voltage range is 2.7V to 5.5V. Connect
IN2 directly to IN1 and IN3. Bypass IN2 to PGND2 with a 1µF ceramic capacitor as close as possible
to the IC. IN2 is high impedance during shutdown.

9 LDO2

200mA LDO Output. Bypass LDO2 to AGND with a 1µF ceramic capacitor. LDO2 is disabled through
the I

2

C interface.

10 LDO1

300mA LDO Output. Bypass LDO1 to AGND with a 2.2µF ceramic capacitor. LDO1 is disabled
through the I

2

C interface.

11 SCL I2C Clock Input. Data is read on the rising edge of V

SCL

.

12 SDA I2C Data Input. Data is read on the rising edge of V

SCL.

.

13 AGND

Analog Ground. Connect AGND to the system ground plane. AGND is also internally connected to
the exposed paddle.

14 REF Refer ence Byp ass. Byp ass RE F w i th a 0.1µF cer am i c cap aci tor to AG N D as cl ose as p ossi b l e to the IC .

15–20

LED1–

LED6

LED Current Regulators. Current flowing into LED_ is based upon the internal I

2

C registers. Connect
LED_ to the cathodes of the external LEDs. LED_ is high impedance during shutdown. If unused,
short LED_ to IN1 to disable the regulator.

21 NEG

Charge-Pump Negative Output. Connect a 1µF ceramic capacitor from NEG to AGND. In shutdown,
an internal 10kΩ resistor connects NEG to AGND.

22 C2N Transfer Capacitor 2 Negative Connection. Connect a 1µF ceramic capacitor from C2P to C2N.

23 C1N Transfer Capacitor 1 Negative Connection. Connect a 1µF ceramic capacitor from C1P to C1N.

24 C2P Transfer Capacitor 2 Positive Connection. Connect a 1µF ceramic capacitor from C2P to C2N.

25 C1P Transfer Capacitor 1 Positive Connection. Connect a 1µF ceramic capacitor from C1P to C1N.

26 IN1

Charge-Pump Supply Voltage Input. The input voltage range is 2.7V to 5.5V. Connect IN1 directly to
IN2 and IN3. Bypass IN1 to PGND1 with a 2.2µF ceramic capacitor as close as possible to the IC.
IN1 is high impedance during shutdown.

27 PGND1 Charge-Pump Power Ground. Connect PGND1 to the system ground plane.

28 IN3

Input Voltage Supply for LDO1, LDO2, REF, Class D Preamplifier, and Class D Amplifier Modulator
Core. The input voltage range is 2.7V to 5.5V. Connect IN3 directly to IN1 and IN2. Bypass IN3 to
AGND with a 2.2µF ceramic capacitor as close as possible to the IC. IN3 is high impedance during
shutdown.

—EP

Exposed Paddle. Connect the exposed paddle to AGND directly under the IC. Exposed paddle is
internally connected to AGND.

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 15

SDA

SCL

PGND1

REF

AGND

LED3

LED4

LED5

LED6

LED1

EP

INVERTING

CHARGE PUMP

CURRENT

SOURCE

CONTROL

IN1

REFERENCE

IN3

LED2

CMREF

SELECT

MINIMUM

I

2

C INTERFACE AND
LOGIC CONTROL

LDO1

LDO2

LDO1

LDO2

SPK+

SPK-

CLASS D
AMP

PGND2

IN2

PGA

AIN-

AIN+

ADAPTIVE

CURRENT

REGULATORS

OSCILLATOR

NEG

NEG

NEG

NEG

NEG

NEG

NEG

REF

PGND2

PGND2

OUTPUT
BUFFER

V

DD

IN3

C2NC2PC1NC1P

MAX8821

+

-

OSCILLATOR

Figure 1. Block Diagram

MAX8821

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

16 ______________________________________________________________________________________

Detailed Description

The MAX8821 integrates a charge pump for white LED
display backlighting, an audio loudspeaker amplifier,
and dual LDO for camera functions. It includes soft­start, thermal shutdown, open-circuit and short-circuit
protections for the white LEDs, audio amplifier, and
LDOs. Figure 1 is the block diagram, and Figure 2
shows the typical application circuit.

LED Charge Pump

The MAX8821 features an inverting charge pump and
six current regulators capable of 25.6mA each to drive

six LEDs. The current regulators are matched to within
±1% (typ), providing uniform white LED brightness for
LCD backlight applications. To maximize efficiency, the
current regulators operate with as little as 0.15V voltage
drop. Individual white LED current regulators conduct
current to GND or NEG to extend usable battery life. In
the case of mismatched forward voltage of white LEDs,
only the white LEDs requiring higher voltage are
switched to direct current to NEG instead of GND, fur­ther raising efficiency and reducing battery current
drain. The regulation scheme is optimized to ensure
low EMI and low input ripple. The on-chip ambient tem­perature derating function safely allows bright 25.6mA

NEG

LED1

LED5

LED4

LED3

LED2

LED6

DUAL LOW­NOISE 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

C7

2.2μF

C3

1μF

C5

2.2μF

C4

0.1μF

C12

0.1μF

C1P C1N

C8

1

μ

F

C2P C2N

C9

1

μ

F

C6
1

μ

F

LDO1

LDO2

C10

2.2

μ

F

C11
1

μ

F

INPUT

2.7 TO 5.5V

MAX8821

Figure 2. Typical Application Circuit

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 17

full-scale output current while automatically reducing
current gradually above +40°C in accordance with
popular LED ratings. The on-chip derating feature can
be enabled, or disabled, using the I

2

C interface.

Current Regulator Switchover

When VINis higher than the forward voltage of the white
LED plus the 0.15V headroom of the current regulator,
the LED current returns through ground. If this condi­tion is satisfied for all six white LEDs the charge pump
remains inactive. When the input voltage drops so that
the current regulator head room cannot be maintained
for any of the individual white LEDs, the inverting
charge pump activates and generates a voltage on
NEG that is no greater than 5V below VIN. Each current
regulator contains circuitry that detects when it is in
dropout and switches that current regulator return path
from GND to NEG. Since this is done on an LED-by­LED basis, the LED current is switched for only the indi­vidual LED requiring higher voltage, thus minimizing
power consumption.

Ramp-Up and Ramp-Down Function

The LED drivers in the MAX8821 provide ramp-up and
ramp-down of LED current for smooth transitions
between different brightness settings. A controlled
ramp is used when the LED current level is changed,
when the LEDs are enabled, and when the LEDs are
disabled. The LED currents ramp up and down smooth­ly on a pseudo-log scaling of the LED current sources
(Figures 3 and 4). Each LED source has an individual
ramp control making it possible to ramp different LEDs
at different rates. The ramp-up and ramp-down (t

RAMP

)
LED current times are controlled by the LED_RU and
LED_RD control bits (Tables 8, 9, and 10). The
LED_RP_EN bit enables and disables the ramps. The
MAX8821 increases/decreases the current one step
every t

RAMP

/32 until the desired current is reached.

Blink Timer

The current regulators for LED5 and LED6 feature a
blink function. The OFF and ON time for LED5 and
LED6 can be set using the I2C interface (Table 11). See
Figure 5.

Combining Blink Timer and Ramp Function

To combine the ramp function together with the blink
timer for LED5 and/or LED6, special timing considera­tions need to be fulfilled. It is recommended to keep the
ramp-up timer shorter than the ON blink timer and the
ramp-down timer shorter than the OFF blink timer.
Failing to comply with these timing constraints results in
the LED_ not reaching the programmed current
(LED_[4:0], Tables 6 and 7) during the ON time and the

LED_ current not returning to 0mA during the off time.
See the following equations to ensure proper operation:

where LED_[4:0] is the programmed current set by I2C
(see Tables 6 and 7).

Figure 6 shows combining ramp function and blink timer.

LED Short- and Open-Circuit Protection

If any LED fails as an open circuit, the corresponding
LED_ is internally connected to ground and the charge
pump is enabled. To disable the corresponding current
regulator, short any unused LED_ to IN1. The MAX8821
contains special circuitry to detect this condition and
disables the corresponding current regulator to avoid
wasting battery power.

Temperature Derating

The MAX8821 contains a derating function that auto­matically limits the LED current at high temperatures in
accordance with the recommended derating curve of
popular white LEDs. The derating function enables the
safe usage of higher LED current at room temperature,
thus reducing the number of LEDs required to backlight
the display. The derating circuit limits the LED current
by reducing the LED current above +40°C at approxi­mately 1.67%/°C. The temperature derating function is
enabled/disabled using the I2C interface and by default
is disabled.

t

t

LED

t

t

LED

ON BLINK

LED RU

OFF BLINK

LED RD

_

_

_

_

(_[:])

(_[:])

≥+

≥+

32

40 1

32

40 1

t

RAMP

=

2097ms

t

RAMP

=

1048ms

t

RAMP

=

524ms

t

RAMP

=

262ms

I

LED_

= 25.6mA

I

LED_

= 0

Figure 3. Ramp-Up Behavior

t

RAMP

=

2097ms

t

RAMP

=

1048ms

t

RAMP

=

524ms

t

RAMP

=

262ms

I

LED_

= 25.6mA

I

LED_

= 0

Figure 4. Ramp-Down Behavior

MAX8821

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

18 ______________________________________________________________________________________

Audio Amplifier

The audio amplifier in the MAX8821 is a 2W Class D
loudspeaker amplifier. The amplifier features a low­power shutdown mode and industry-leading click-and­pop suppression. The amplifier also features a
programmable gain control through an I

2

C interface.
The amplifier operates from a single 2.7V to 5.5V sup­ply (V

IN3

= V

IN2

) and features an internally generated

common-mode bias voltage of V

IN3

/ 2 referenced to

ground.

Click-and-Pop Suppression

The MAX8821 features Maxim’s industry-leading click­and-pop suppression circuitry. During startup, the
amplifier’s common-mode bias voltage ramps to the
DC bias point. When entering shutdown, the amplifier
outputs are high impedance with 100kΩ between both
inputs. This scheme minimizes the energy present in
the audio band.

Class D Amplifier

The MAX8821 ultra-low-EMI, filterless, Class D audio
power amplifier features several improvements to
switch mode amplifier technology. The MAX8821 audio
amplifier features output driver AEL circuitry to reduce
EMI. Zero dead-time technology maintains state-of-the­art efficiency and THD+N performance by allowing the
output MOSFETs to switch simultaneously without
cross-conduction.

A unique filterless modulation scheme and spread­spectrum mode create a compact, flexible, low-noise,
efficient audio power amplifier while occupying minimal
board space. The differential input architecture reduces
common-mode noise pickup with or without the use of
input-coupling capacitors. The MAX8821 audio amplifier
can also be configured as a single-ended input amplifier
without performance degradation. The input capacitors
C

IN

(Figure 7) are required for single-ended input appli-

cations and are typically 1µF.

The output of the MAX8821 shuts down if the output cur­rent reaches approximately 2A. Each output MOSFET
has its own short-circuit protection. This protection
scheme allows the amplifier to survive shorts to either
supply rail. After a thermal overload or short circuit, the
device remains disabled for a minimum of 110µs before
attempting to return to normal operation. The amplifier
shuts down immediately and waits another 110µs before
turning on if the fault condition remains. This operation
causes the output to pulse during a persistent fault.

Comparators monitor the MAX8821 inputs and compare
the complementary input voltages to the sawtooth wave­form. The comparators trip when the input magnitude of
the sawtooth exceeds their corresponding input voltage.

Both comparators reset at a fixed time after the rising
edge of the second comparator trip point, generating a
minimum width pulse t

ON(MIN)

at the output of the sec­ond comparator. As the input voltage increases or
decreases, the duration of the pulse at one output
increases (the first comparator to trip), while the other
output pulse duration remains at t

ON(MIN)

. This causes
the net voltage across the speaker (SPK+ - SPK-)
to change.

Adjustable Differential Gain

The audio amplifier has an internal gain control. The
gain of the input amplifiers is controlled through the I2C
interface. The gain setting of the input amplifier can be
set from -3dB to +24dB (Table 15). This allows the
amplifier to be used for both hands-free and for receiv­er mode without any external components.

Input Filter

The fully differential amplifier inputs can be biased at
voltages other than midsupply. The common-mode
feedback circuit adjusts for input bias, ensuring the
outputs are still biased at midsupply. Input capacitors
are not required as long as the common-mode input
voltage is within the specified range listed in the

Electrical Characteristics

table. If input capacitors are
used, input capacitor CIN, in conjunction with on-chip
R

INT

, forms a highpass filter that removes the DC bias
from an incoming signal. The AC-coupling capacitor
allows the amplifier to bias the signal to an optimum DC
level. Assuming zero-source impedance, the -3dB point
of the highpass filter is given by:

Setting the -3dB corner too high affects the low-fre­quency response of the amplifier. Use capacitors with
dielectrics that have low-voltage coefficients, such as
aluminum electrolytic. Capacitors with high voltage
coefficients, such as ceramics, can increase distortion
at low frequencies.

f

RC

dB

INT IN

−

=

×× ×

3

1

2 π

64ms = t

ON_BLINK

= 512ms

0.512s = t

OFF_BLINK

= 4.098s

ILED6[4:0]

ILED5[4:0]

Figure 5. Blink Timer Behavior

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 19

LDO1 and LDO2

The linear regulators are designed for low dropout and
low quiescent current to maximize battery life. Both
LDOs are controlled through the I2C interface, minimiz­ing the number of control lines to the MAX8821. Each
LDO has an individual control register (LDO1_CNTL
and LDO2_CNTL, Tables 13 and 14). The I2C interface
controls the output voltages, and the enable/disable
state for both LDO1 and LDO2.

Thermal Shutdown

The MAX8821 includes a thermal-limit circuit that shuts
down the IC at a junction temperature of approximately
+160°C. The IC turns on after it cools by approximately
20°C.

Shutdown Mode

The MAX8821 can be put into two different shutdown
modes. The first shutdown mode is achieved by driving
VDDlow. In this mode, the I2C interface becomes dis­abled. The second shutdown is a lower power mode.
To enter the low-power mode, disable LED_, audio
amplifier, and LDOs through I2C. In lower power mode,
the I2C interface is still active.

I2C Interface

The I2C serial interface consists of a serial-data line
(SDA) and a serial-clock line (SCL). Standard I2C write­byte commands are used. Figure 8 shows a timing dia­gram for the I2C protocol. The MAX8821 is a slave-only
device, relying upon a master to generate a clock sig­nal. The master (typically a microprocessor) initiates
data transfer on the bus and generates SCL to permit
data transfer. A master device communicates to the
MAX8821 by transmitting the proper 8-bit address fol­lowed by the 8-bit control byte. Each transmit
sequence is framed by a START (A) condition and a
STOP (L) condition. Each word transmitted over the bus

is 8 bits long and is always followed by an acknowl­edge clock pulse (K).

Both SCL and SDA remain high when the interface is
not busy. A master signals the beginning of a transmis­sion with a START (A) condition by transitioning SDA
from high to low while SCL is high. When the master
has finished communicating with the slave, the master
issues a STOP (L) condition by transitioning SDA from
low to high while SCL is high. The bus is then free for
another transmission. One data bit is transferred during
each clock pulse. The data on SDA must remain stable
while SCL is high.

Register Reset

The I2C register is reset back to the default value when
either V

IN_

drops below the UVLO threshold or VDDis

driven low.

I2C Registers and Control

I

2

C Address

The MAX8821 acts as a slave transmitter/receiver. The
slave address of the MAX8821 is preset to 1001110X,
where “X” is the R/W bit. The address 0x9C is designat­ed for write operations and 0x9D for read operations.

Use Table 1 as a register map to reference the control
bits found in Tables 2–16.

t

OFF_BLINK

t

ON_BLINK

t

OFF_BLINK

ILED_ = LED_ [4.0]

ILED_ = 0mA

t = t

LED_RU

/32 t = t

LED_RD

/32

Figure 6. Combining Ramp Function and Blink Timer (Tables 10 and 11)

MONO

CLASS D

AUDIO AMP

EARPIECE/
LOUDSPEAKER

CIN

CIN

R

INT

R

INT

MAX8821

AUDIO

INPUTS

Figure 7. Optional Input Capacitors

MAX8821

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

20 ______________________________________________________________________________________

SCL

A

B

C

D

E F

G

H

I

J

K

SDA

t

HD_STA

L

M

J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION

t

BUF

t

LOW

t

HIGH

t

SU_STA

t

SU_DAT

t

HD_DAT

t

SU_STO

F = ACKNOWLEDGE BIT CLOCKED INTO MASTER
G = MSB OF DATA CLOCKED INTO SLAVE (OP/SUS BIT)
H = LSB OF DATA CLOCKED INTO SLAVE
I = SLAVE PULLS SMBDATA LINE LOW

A = START CONDITION
B = MSB OF ADDRESS CLOCKED INTO SLAVE
C = LSB OF ADDRESS CLOCKED INTO SLAVE
D = R/W BIT CLOCKED INTO SLAVE
E = SLAVE PULLS SMBDATA LINE LOW

Figure 8. I2C Timing Diagram

NAME

GROUP ADDRESS

(hexadecimal)

TABLE TYPE DESCRIPTION

LED1_CNTL 00 2 R/W LED1 current regulator control

LED2_CNTL 01 3 R/W LED2 current regulator control

LED3_CNTL 02 4 R/W LED3 current regulator control

LED4_CNTL 03 5 R/W LED4 current regulator control

LED5_CNTL 04 6 R/W LED5 current regulator control

LED6_CNTL 05 7 R/W LED6 current regulator control

RAMP1_CNTL 06 8 R/W LED1 and LED2 ramp control

RAMP2_CNTL 07 9 R/W LED3 and LED4 ramp control

RAMP3_CNTL 08 10 R/W LED5 and LED6 ramp control

BLINK_CNTL 09 11 R/W LED5 and LED6 blink control

LED_EN 0A 12 R/W LED1–LED6 enable control

LDO1_CNTL 0B 13 R/W LDO1 control

LDO2_CNTL 0C 14 R/W LDO2 control

AUDIO_CNTL 0D 15 R/W

Audio amplifier, control clock, and frequency

PUMP_CNTL 0E 16 R/W

Charge-pump control setting and temperature
derating enable/disable

Table 1. Register Map

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 21

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

B5 LED1_RP_EN

0

1

LED1 ramp-up/down
disabled.

LED1 ramp-up/down
enabled.

00000 0.1mA

00001 0.2mA

00010 0.3mA

00011 0.4mA

00100 0.5mA

00101 0.6mA

00110 0.7mA

00111 0.8mA

01000 1.0mA

01001 1.2mA

01010 1.4mA

01011 1.6mA

01100 2.0mA

01101 2.4mA

01110 2.8mA

01111 3.2mA

10000 4.0mA

10001 4.8mA

10010 5.6mA

10011 6.4mA

10100 8.0mA

10101 9.6mA

10110 11.2mA

10111 12.8mA

11000 14.4mA

11001 16.0mA

11010 17.6mA

11011 19.2mA

11100 20.8mA

11101 22.4mA

11110 24.0mA

B4–B0 LED1[4:0]

11111 25.6mA

Table 2. LED1_CNTL (Address 0x00)

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

B5 LED2_RP_EN

0

1

LED2 ramp-up/down
disabled.

LED2 ramp-up/down
enabled.

00000 0.1mA

00001 0.2mA

00010 0.3mA

00011 0.4mA

00100 0.5mA

00101 0.6mA

00110 0.7mA

00111 0.8mA

01000 1.0mA

01001 1.2mA

01010 1.4mA

01011 1.6mA

01100 2.0mA

01101 2.4mA

01110 2.8mA

01111 3.2mA

10000 4.0mA

10001 4.8mA

10010 5.6mA

10011 6.4mA

10100 8.0mA

10101 9.6mA

10110 11.2mA

10111 12.8mA

11000 14.4mA

11001 16.0mA

11010 17.6mA

11011 19.2mA

11100 20.8mA

11101 22.4mA

11110 24.0mA

B4–B0 LED2[4:0]

11111 25.6mA

Table 3. LED2_CNTL (Address 0x01)

Note: Defaults in bold italics.

Note: Defaults in bold italics.

MAX8821

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

22 ______________________________________________________________________________________

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

B5 LED3_RP_EN

0

1

LED3 ramp-up/down
disabled.

LED3 ramp-up/down
enabled.

00000 0.1mA

00001 0.2mA

00010 0.3mA

00011 0.4mA

00100 0.5mA

00101 0.6mA

00110 0.7mA

00111 0.8mA

01000 1.0mA

01001 1.2mA

01010 1.4mA

01011 1.6mA

01100 2.0mA

01101 2.4mA

01110 2.8mA

01111 3.2mA

10000 4.0mA

10001 4.8mA

10010 5.6mA

10011 6.4mA

10100 8.0mA

10101 9.6mA

10110 11.2mA

10111 12.8mA

11000 14.4mA

11001 16.0mA

11010 17.6mA

11011 19.2mA

11100 20.8mA

11101 22.4mA

11110 24.0mA

B4–B0 LED3[4:0]

11111 25.6mA

Table 4. LED3_CNTL (Address 0x02)

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

B5 LED4_RP_EN

0

1

LED4 ramp-up/down
disabled.

LED4 ramp-up/down
enabled.

00000 0.1mA

00001 0.2mA

00010 0.3mA

00011 0.4mA

00100 0.5mA

00101 0.6mA

00110 0.7mA

00111 0.8mA

01000 1.0mA

01001 1.2mA

01010 1.4mA

01011 1.6mA

01100 2.0mA

01101 2.4mA

01110 2.8mA

01111 3.2mA

10000 4.0mA

10001 4.8mA

10010 5.6mA

10011 6.4mA

10100 8.0mA

10101 9.6mA

10110 11.2mA

10111 12.8mA

11000 14.4mA

11001 16.0mA

11010 17.6mA

11011 19.2mA

11100 20.8mA

11101 22.4mA

11110 24.0mA

B4–B0 LED4[4:0]

11111 25.6mA

Table 5. LED4_CNTL (Address 0x03)

Note: Defaults in bold italics. Note: Defaults in bold italics.

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 23

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

B5 LED5_RP_EN

0

1

LED5 ramp-up/down
disabled.

LED5 ramp-up/down
enabled.

00000 0.1mA

00001 0.2mA

00010 0.3mA

00011 0.4mA

00100 0.5mA

00101 0.6mA

00110 0.7mA

00111 0.8mA

01000 1.0mA

01001 1.2mA

01010 1.4mA

01011 1.6mA

01100 2.0mA

01101 2.4mA

01110 2.8mA

01111 3.2mA

10000 4.0mA

10001 4.8mA

10010 5.6mA

10011 6.4mA

10100 8.0mA

10101 9.6mA

10110 11.2mA

10111 12.8mA

11000 14.4mA

11001 16.0mA

11010 17.6mA

11011 19.2mA

11100 20.8mA

11101 22.4mA

11110 24.0mA

B4–B0 LED5[4:0]

11111 25.6mA

Table 6. LED5_CNTL (Address 0x04)

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

B5 LED6_RP_EN

0

1

LED6 ramp-up/down
disabled.

LED6 ramp-up/down
enabled.

00000 0.1mA

00001 0.2mA

00010 0.3mA

00011 0.4mA

00100 0.5mA

00101 0.6mA

00110 0.7mA

00111 0.8mA

01000 1.0mA

01001 1.2mA

01010 1.4mA

01011 1.6mA

01100 2.0mA

01101 2.4mA

01110 2.8mA

01111 3.2mA

10000 4.0mA

10001 4.8mA

10010 5.6mA

10011 6.4mA

10100 8.0mA

10101 9.6mA

10110 11.2mA

10111 12.8mA

11000 14.4mA

11001 16.0mA

11010 17.6mA

11011 19.2mA

11100 20.8mA

11101 22.4mA

11110 24.0mA

B4–B0 LED6[4:0]

11111 25.6mA

Table 7. LED6_CNTL (Address 0x05)

Note: Defaults in bold italics.

Note: Defaults in bold italics.

MAX8821

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

24 ______________________________________________________________________________________

BIT NAME DESCRIPTION CODE RAMP TIME (t

RAMP

) (ms)

B7, B6 LED1_RU[1:0] LED1 ramp-up control 00 2

18

x T

QPCLK

B5, B4 LED1_RD[1:0] LED1 ramp-down control 01 219 x T

QPCLK

B3, B2 LED2_RU[1:0] LED2 ramp-up control 10 2

20

x T

QPCLK

B1, B0 LED2_RD[1:0] LED2 ramp-down control 11 2

21

x T

QPCLK

Table 8. RAMP1_CNTL (Address 0x06)

Notes: T

QPCLK

= 1 / fSW; defaults in bold italics.

BIT NAME DESCRIPTION CODE RAMP TIME (t

RAMP

) (ms)

B7, B6 LED3_RU[1:0] LED3 ramp-up control 00 2

18

x T

QPCLK

B5, B4 LED3_RD[1:0] LED3 ramp-down control 01 2

19

x T

QPCLK

B3, B2 LED4_RU[1:0] LED4 ramp-up control 10 2

20

x T

QPCLK

B1, B0 LED4_RD[1:0] LED4 ramp-down control 11 2

21

x T

QPCLK

Table 9. RAMP2_CNTL (Address 0x07)

Notes: T

QPCLK

= 1 / fSW; defaults in bold italics.

BIT NAME DESCRIPTION CODE RAMP TIME (t

RAMP

) (ms)

B7, B6 LED5_RU[1:0] LED5 ramp-up control 00 2

18

x T

QPCLK

B5, B4 LED5_RD[1:0] LED5 ramp-down control 01 2

19

x T

QPCLK

B3, B2 LED6_RU[1:0] LED6 ramp-up control 10 2

20

x T

QPCLK

B1, B0 LED6_RD[1:0] LED6 ramp-down control 11 2

21

x T

QPCLK

Table 10. RAMP3_CNTL (Address 0x08)

Notes: T

QPCLK

= 1 / fSW; defaults in bold italics.

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 25

BIT NAME CODE BLINK TIME

00 219 x T

QPCLK

01 220 x T

QPCLK

10 221 x T

QPCLK

B7, B6 LED5_OFF_BLINK

11 2

22

x T

QPCLK

00 216 x T

QPCLK

01 217 x T

QPCLK

10 218 x T

QPCLK

B5, B4 LED5_ON_BLINK

11 2

19

x T

QPCLK

00 219 x T

QPCLK

01 220 x T

QPCLK

10 221 x T

QPCLK

B3, B2 LED6_OFF_BLINK

11 2

22

x T

QPCLK

00 216 x T

QPCLK

01 217 x T

QPCLK

10 218 x T

QPCLK

B1, B0 LED6_ON_BLINK

11 2

19

x T

QPCLK

Table 11. BLINK_CNTL (Address 0x09)

Notes: T

QPCLK

= 1 / fSW; defaults in bold italics.

BIT NAME CODE DESCRIPTION

B7 LED1_EN

B6 LED2_EN

0

LED current source is
disabled.

B5 LED3_EN

B4 LED4_EN

1

LED current source is
enabled.

00

LED current source is
disabled.

B3, B2 LED5_EN[1:0]

01

LED current source is
enabled.

10

LED current source
controlled by blink
timer.

B1, B0 LED6_EN[1:0]

11 N/A, do not use.

Table 12. LED_EN (Address 0xA)

Note: Defaults in bold italics.

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

0 LDO1 is disabled.

B5 LDO1_EN

1 LDO1 is enabled.

0

Active pulldown enabled
during OFF condition.

B4 LDO1_PD

1

Active pulldown disabled
during OFF condition.

0000 1.2V

0001 1.3V

0010 1.5V

0011 1.6V

0100 1.8V

0101 1.9V

0110 2.0V

0111 2.3V

1000 2.5V

1001 2.6V

1010 2.7V

1011 2.8V

1100 2.9V

1101 3.0V

1110 3.1V

B3–B0 LDO1[3:0]

1111 3.2V

Table 13. LDO1_CNTL (Address 0x0B)

Note: Defaults in bold italics.

MAX8821

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

26 ______________________________________________________________________________________

BIT NAME CODE DESCRIPTION

B7, B6 N/A, do not use.

0 LDO2 is disabled.

B5 LDO2_EN

1 LDO2 is enabled.

0

Active pulldown enabled
during OFF condition.

B4 LDO2_PD

1

Active pulldown disabled
during OFF condition.

0000 1.5V

0001 1.6V

0010 1.8V

0011 2.0V

0100 2.2V

0101 2.3V

0110 2.4V

0111 2.5V

1000 2.6V

1001 2.7V

1010 2.8V

1011 2.9V

1100 3.0V

1101 3.1V

1110 3.2V

B3–B0 LDO2[3:0]

1111 3.3V

Table 14. LDO2_CNTL (Address 0x0C)

Note: Defaults in bold italics.

BIT NAME CODE DESCRIPTION

0

Audio amplifier and
charge-pump
clocks are not
synchronized.

B7 SYNC

1

Audio amplifier and
charge-pump clocks
are synchronized.
Charge pump
oscillator clock =
audio clock / 2.

00

O s c illa t o r f r e q u e n c y
1 1 0 0 k H z, f ix e d ­f r e q u e n c y m o d e .

01

Oscillator frequency
1400kHz, fixed­frequency mode.

10

Oscillator frequency
1250kHz, spread­spectrum mode.

B6, B5 CLK_CNTL[1:0]

11

Reserved for future
use.

B4 AMP_EN

0

1

Class D amplifier is
disabled.

Class D amplifier is
enabled.

0000 -3dB

0001 0dB

0010 3dB

0011 6dB

0100 9dB

0101 12dB

0110 15dB

0111 18dB

1000 21dB

1001 24dB

1010 N/A, do not use.

1011 N/A, do not use.

1100 N/A, do not use.

1101 N/A, do not use.

1110 N/A, do not use.

B3–B0 AUDIO_GAIN[3:0]

1111 N/A, do not use.

Table 15. AUDIO_CNTL (Address 0x0D)

Note: Defaults in bold italics.

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

______________________________________________________________________________________ 27

Applications Information

PCB Layout

PCB layout is essential for optimizing performance. Use
large traces for the power-supply inputs and amplifier
outputs to minimize losses due to parasitic trace resis­tance and to route heat away from the device. To avoid
potential noise to the differential input audio signal and
differential output audio signal, route the negative and
positive traces in parallel. Also, avoid placing any RF or
high-speed data signals in parallel to the audio signals.
In some applications, such as GSM, extra noise reduc­tion may be needed. To reduce the risk of noise, place
16pF ceramic capacitors from AIN+ to AGND, AIN- to
AGND, OUT+ to AGND, OUT- to AGND, OUT+ to OUT-,
and AIN+ to AIN-.

Proper grounding improves audio performance and
prevents any digital switching noise from coupling into
the audio signal. The Thin QFN package features an
exposed thermal paddle on its undersides. This paddle
lowers the thermal resistance of the package by provid­ing a direct-heat conduction path from the die to the
PCB. Connect the exposed paddle to AGND directly
under the IC. Refer to the MAX8821 Evaluation Kit for
an example of a PCB layout.

BIT NAME CODE DESCRIPTION

B7–B3 N/A, do not use

0

Temperature
derating disabled.

B2 TEMP_DR

1

Temperature derating
enabled.

00

Charge pump
automatically
changes between
1x/1.5x mode.

01

Charge pump is
forced into 1.5x mode
regardless of input
voltage.

10

Charge pump is
forced into 1.5x mode
regardless of input
voltage when audio
amplifier is enabled. If
the amplifier is not
enabled, the charge
pump automatically
switches between 1x
mode and 1.5x mode.

B1, B0 PUMP_CNTL [1:0]

11 N/A, do not use.

Table 16. PUMP_CNTL (Address 0x0E)

Note: Defaults in bold italics.

26

27

25

24

10

9

11

CMREF

AIN-

PGND2

SPK-

SPK+

12

V

DD

LED6

LED4

LED3

NEG

LED2

LED1

12

C1P

4567

2021 19 17 16 15

IN1

PGND1

SDA

SCL

LDO1

LDO2

MAX8821ETI+

AIN+

LED5

3

18

28

8

IN3

IN2

C2P

23

13

AGND

C1N

22

14

REF

C2N

TOP VIEW

+

EP = EXPOSED PADDLE

Pin Configuration

Chip Information

PROCESS: BiCMOS

MAX8821

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

28 ______________________________________________________________________________________

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)

24L QFN THIN.EPS

MAX8821

White LED Charge Pump with Mono Class D

Audio Amp and Dual LDO

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.

Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________

29

© 2007 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.

Package Information (continued)

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages

.)