MAXIM MAX8821

19-1014; Rev 0; 10/07
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
The MAX8821 integrates a charge pump for white
LEDs, an audio loudspeaker amplifier, and two lownoise LDOs controlled by an I2C 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 I2C
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 (VF) 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).
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
TA Derating Function Protects LEDs
♦ Mono 2W Class D Loudspeaker Amplifier
85% Efficiency (RL = 8Ω, POUT = 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
45µVRMS Output Noise, 70dB PSRR
Flexible I2C-Controlled Output Voltages
200mA and 300mA Output Current Drive
Ordering Information
PART
MAX8821ETI+
TEMP RANGE
-40°C to +85°C
PINPACKAGE
28 Thin QFN
4mm x 4mm
PKG
CODE
T2844-1
+Denotes a lead-free package.
Typical Operating Circuit
INPUT
2.7 TO 5.5V
C1P
C1N
C2P
C2N
IN1
NEG
PGND1
IN2
Applications
PGND2
LED1
IN3
LED2
AGND
Cell Phones and Smartphones
MAX8821
REF
LED3
LED4
PDAs, Digital Cameras, Camcorders
LED5
MP3 Players, GPS Devices
LED6
INDIVIDUAL
0.1mA TO
25.6mA
DIMMING
CMREF
LDO1
LOGIC
CONTROL AND I2C
INTERFACE
DIFFERENTIAL
AUDIO INPUT
DUAL LOW
NOISE LDO
VDD
LDO2
SDA
SCL
SPK+
AIN+
AIN-
SPK-
LOUDSPEAKER/
EARPIECE
EP
________________________________________________________________ Maxim Integrated Products
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.
1
MAX8821
General Description
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
ABSOLUTE MAXIMUM RATINGS
IN1, IN2, IN3, VDD to AGND..................................-0.3V to +6.0V
SCL, SDA to AGND ....................................-0.3V to (VDD + 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 (VIN1 + 0.3V)
LED_, C1N, C2N to NEG............................-0.3V to (VIN1 + 0.3V)
LDO1, LDO2, REF to AGND ......................-0.3V to (VIN3 + 0.3V)
CMREF, AIN+, AIN-, SPK+, SPKto AGND..................................................-0.3V to (VIN2 + 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 (TA = +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
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.
ELECTRICAL CHARACTERISTICS
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
VIN1, VIN2, VIN3 Operating
Voltage
VDD Operating Range
Undervoltage Lockout (UVLO)
Threshold
CONDITIONS
VIN3 rising
MIN
MAX
UNITS
2.7
5.5
V
1.5
5.5
V
2.65
V
2.25
2.45
0.450
0.865
1.350
TA = +25°C
0.1
1
TA = +85°C
0.1
TA = +25°C
2
UVLO Hysteresis
100
VDD Shutdown Threshold
IN1, IN2, IN3 Shutdown Supply
Current
(All Outputs Off)
TYP
VDD = AGND
VDD = 3.6V
mV
10
TA = +85°C
2
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
Charge pump active, 1MHz switching, all LEDs at
25.6mA setting, audio amplifier disabled, LDO1 and
LDO2 disabled
1.50
4.00
LED driver disabled, audio amplifier enabled, LDO1 and
LDO2 disabled
6.6
V
µA
µA
No-Load Supply Current
mA
Thermal Shutdown
Thermal-Shutdown Hysteresis
20
+160
°C
20
°C
CHARGE PUMP
SYNC = 0
Switching Frequency
(fSW)
450
550
650
SYNC = 1, SW_MODE = 01
575
700
825
SYNC = 1, SW_MODE = 10
2
1000
SYNC = 1, SW_MODE = 00
625
± 25
_______________________________________________________________________________________
kHz
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
CONDITIONS
MIN
Soft-Start Time
Regulation Voltage
(VIN1 - VNEG)
Open-Loop NEG Output
Resistance
(0.5 x VIN1 - VNEG) / INEG
Output Current
VIN1 = 3.2V, LED VFMAX = 3.9V
NEG Discharge Resistance in
Shutdown
All LEDs disabled
TYP
MAX
UNITS
0.1
ms
5
V
1.75
3.5
154
Ω
mA
10
kΩ
LED_ CURRENT REGULATORS
Current Setting Range
ILED_
25.6mA setting
Current Accuracy
0.1
TA = +25°C
-2
TA = -40°C to derating
function start temperature
(enabled by I2C)
-5
0.1mA setting, TA = +25°C
-30
Current-Derating-Function Start
Temperature
Current-Derating-Function Slope
RDS ON
°C
-1.67
Charge pump inactive
2.3
4.6
5
14
Charge pump inactive
72
120
Charge pump active
120
360
150
175
25.6mA setting (Note 2)
Current Regulator
Switchover Threshold
Charge pump inactive to active,
VLED_ falling
125
Current Regulator
Switchover Hysteresis
%/°C
100
Leakage Current in Shutdown
All LEDs
disabled
Off Blink Time
B7, B6 or B3, B2,
SYNC = 0,
Table 11
TA = +25°C
0.01
TA = +85°C
0.1
B5, B4 or B1, B0,
SYNC = 0,
Table 11
LED__RU: B7, B6 or B3, B2
LED__RD: B5, B4 or B1, B0
SYNC = 0,
Tables 8, 9, 10 (Note 3)
00
524
01
1048
10
2097
11
4194
00
66
01
131
10
262
11
524
00
262
01
524
10
1048
11
2097
%
+30
TA = +40°C to +85°C
Dropout Voltage
Ramp-Up/Down Time
+5
±5
mA
+2
+40
Charge pump active
On Blink Time
25.6
±1
Ω
mV
mV
mV
1
µA
ms
ms
ms
_______________________________________________________________________________________
3
MAX8821
ELECTRICAL CHARACTERISTICS (continued)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
ELECTRICAL CHARACTERISTICS (continued)
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
AUDIO AMPLIFIER
Common-Mode Bias Voltage
Output Offset Voltage
0.95 x
1.05 x
V
/2
(VIN3 / 2) IN3
(VIN3 / 2)
V
±1
mV
VAIN+ = VAIN- = VIN3 / 2, audio gain = 0dB
Common-Mode Input Voltage
VIN3 1.2V
0.5
V
-3
0
3
6
Audio Gain
9
Table 15, B3:B0
dB
12
15
18
21
24
Audio Gain Accuracy
Input Resistance
Common-Mode Rejection Ratio
-3
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
Audio gain = 24dB
8.2
15.0
22.0
VIN2 = VIN3 = 3.6V
46
f = 1kHz, VIN2 = VIN3 = 3.6V
46
Power-Supply Rejection Ratio
VAIN+ = VAIN- = VIN3 / 2,
100mVP-P at VIN3
Output Power
THD+N = 1%,
f = 1kHz
(Note 4)
Total Harmonic Distortion Plus
Noise
4
+3
Audio gain = -3dB
VIN3 = 3.6V
VIN3 = 5V
RL = 8Ω, f = 1kHz, POUT = 0.25W,
VIN2 = VIN3 = 3.6V
f = 217Hz
65
f = 20kHz
50
RL = 8Ω
0.36
RL = 4Ω
RL = 8Ω
RL = 4Ω
kΩ
dB
dB
0.5
0.85
0.8
%
1.1
W
2.0
0.05
_______________________________________________________________________________________
%
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
CONDITIONS
Signal-to-Noise Ratio
RL = 8Ω, f = 1kHz,
POUT = 0.25W,
VIN2 = VIN3 = 3.6V
MIN
91
Spread-spectrum mode (SSM)
89
FFM A weighted
93
SSM A weighted
Oscillator Frequency
(fosc)
TYP
Fixed-frequency mode (FFM)
MAX
UNITS
dB
91
SW_MODE = 00
900
1100
1300
SW_MODE = 01
1150
1400
1650
kHz
SW_MODE = 10
1250
±50
Differential Input
Resistance
Shutdown mode only
100
kΩ
Output Current Limit
SPK+, SPK- short circuited to PGND2 or to IN2
2
A
110
µs
Wake-Up Delay After
Short Circuit
LDO1
Output Voltage VLDO1
3.6V ≤ VIN3 ≤ 5.5V,
1mA ≤ ILDO1 ≤ 300mA
Maximum Output
Current
1.164
1.200
1.236
300
400
V
mA
Output Current Limit
VLDO1 = 0V
650
1000
mA
Dropout Voltage
ILDO1 = 200mA, TA = +25°C (Note 5)
150
300
mV
Line Regulation
VIN3 stepped from 3.4V to 5.5V,
ILDO1 = 150mA
2.4
mV
Load Regulation
ILDO1 stepped from 1mA to 300mA
25
mV
Power-Supply
Rejection
ΔVIN3/ΔVLDO1
10Hz to 10kHz,
ILDO1 = 30mA
70
dB
Output Voltage Noise
(RMS)
100Hz to 100kHz,
ILDO1 = 30mA
45
µVRMS
_______________________________________________________________________________________
5
MAX8821
ELECTRICAL CHARACTERISTICS (continued)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
ELECTRICAL CHARACTERISTICS (continued)
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
Programmable Output
Voltage
Shutdown Output
Impedance
CONDITIONS
ILDO1 = 50mA
control bits B3:B0;
see Table 13
MIN
TYP
MAX
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
1111
3.104
3.2
3.296
LDO1 disabled through I2C
1
UNITS
V
kΩ
LDO2
Output Voltage VLDO2
3.6V ≤ VIN3 ≤ 5.5V,
1mA ≤ ILDO2 ≤ 200mA
Maximum Output
Current
1.455
1.500
1.545
200
mA
Output Current Limit
VLDO2 = 0V
550
750
mA
Dropout Voltage
ILDO2 = 133mA, TA = +25°C (Note 5)
100
200
mV
Line Regulation
VIN3 stepped from 3.4V to 5.5V, ILDO2 = 100mA
2.4
mV
Load Regulation
ILDO2 stepped from 1mA to 200mA
25
mV
Power-Supply
Rejection
ΔVIN3/ΔVLDO2
10Hz to10kHz,
ILDO2 = 20mA
70
dB
Output Voltage Noise
(RMS)
100Hz to100kHz,
ILDO2 = 20mA
45
µVRMS
6
250
V
_______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
CONDITIONS
Programmable Output
Voltage
Shutdown Output
Impedance
ILDO2 = 50mA
control bits
B3:B0;
see Table 14
MIN
TYP
MAX
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
1111
3.201
3.3
3.399
LDO2 disabled through I2C
1
UNITS
V
kΩ
I2C INTERFACE (Figure 8)
Logic Input High
Voltage
0.7 x
VDD
V
Logic Input Low
Voltage
0.3 x
VDD
Logic Input Current
VIL = 0V or VIH = VDD
SDA Output Low
Voltage
ISDA = 3mA
TA = +25°C
-1
TA = +85°C
0.01
+1
0.1
0.03
I2C Clock Frequency
V
µA
0.4
V
400
kHz
Bus-Free Time
Between START and
STOP
tBUF
1.3
Hold Time Repeated
START Condition
tHD_STA
0.6
0.1
µs
SCL Low Period
tLOW
1.3
0.2
µs
SCL High Period
tHIGH
0.6
0.2
µs
Setup Time Repeated
START Condition
tSU_STA
0.6
0.1
µs
µs
_______________________________________________________________________________________
7
MAX8821
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
MIN
TYP
SDA Hold Time
PARAMETER
tHD_DAT
0
-0.01
µs
SDA Setup Time
tSU_DAT
100
50
ns
Setup Time for STOP
Condition
tSU_STO
0.6
0.1
µs
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
CONDITIONS
MAX
UNITS
Limits are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by design.
Dropout voltage is defined as the LED_ to GND voltage when the current into LED_ drops 10% from the value at VLED_ = 0.5V.
Ramp-up time is from 0mA to full scale; ramp-down time is from full scale to 0mA.
Output power is specified by a combination of a functional output current test and characterization analysis.
The dropout voltage is defined as VIN_ - VOUT when VOUT is 100mV below the nominal value of VOUT. The specification only
applies when VOUT ≥ 3.0V.
Typical Operating Characteristics
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = +25°C, unless otherwise noted.)
LED CHARGE PUMP
60
20.8mA/LED
50
1.6mA/LED
16mA/LED
6.4mA/LED
40
70
60
30
20
20
2.7
3.0
3.3
3.6
3.9
6.4mA/LED
80
6.4mA/LED
70
1.6mA/LED
16mA/LED
60
20.8mA/LED
LEDs HAVE
20.8mA/LED
HIGH MATCHED VF
LEDs HAVE MISMATCHED VF
40
0
4.2
90
50
10
LEDs HAVE MATCHED VF
0
16mA/LED
1.6mA/LED
40
30
10
20.8mA/LED
50
100
MAX8821 toc03
80
EFFICIENCY (%)
70
90
2.7
3.0
3.3
3.6
3.9
4.2
4.2 3.9
3.8
3.7
3.6
3.5 3.4 3.0
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
Li+ BATTERY VOLTAGE (V, TIME-WEIGHTED)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (DRIVING SIX LEDs)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE (RGB MODULE)
LED CURRENT MATCHING
vs. SUPPLY VOLTAGE (16mA/LED)
175
SUPPLY CURRENT (mA)
ILED = 16mA
150
125
100
ILED = 6.4mA
75
50
ILED = 1.6mA
RGB MODULE: LUMEX SML-LX3632SISUGSBC
60
ILED = 20.8mA
ILED = 16mA
50
40
30
ILED = 6.4mA
20
2.7
3.2
3.7
SUPPLY VOLTAGE (V)
4.2
16.3
16.2
16.1
16.0
15.9
15.8
15.6
CHARGE PUMP IN 1.5x
15.5
0
0
16.4
15.7
ILED = 1.6mA
10
25
16.5
MAX8821 toc06
200
70
LED CURRENT (mA)
LEDs HAVE HIGH MISMATCHED VF
ILED = 20.8mA
225
MAX8821 toc05
250
MAX8821 toc04
EFFICIENCY (%)
80
MAX8821 toc02
90
8
100
MAX8821 toc01
100
EFFICIENCY vs. Li+ BATTERY VOLTAGE
DRIVING SIX LEDs
EFFICIENCY vs. SUPPLY VOLTAGE
(DRIVING SIX LEDS)
EFFICIENCY PLED/PBATT (%)
EFFICIENCY vs. SUPPLY VOLTAGE
(DRIVING SIX LEDS)
SUPPLY CURRENT (mA)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
2.7
3.2
3.7
SUPPLY VOLTAGE (V)
4.2
2.7
3.1
3.5
3.9
4.3
4.7
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________
5.1
5.5
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
1x MODE OPERATING
WAVEFORMS (VIN = 4V)
LED CURRENT vs. AMBIENT
TEMPERATURE
MAX8821 toc08
MAX8821 toc07
30
25
AC-COUPLED
100mV/div
LED CURRENT (mA)
VIN
20
MAX8821
Typical Operating Characteristics (continued)
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = +25°C, unless otherwise noted.)
2V/div
0V
VNEG
15
200mA/div
IIN
10
0A
20mA/div
5
ILED
CURRENT DERATING ENABLED
ALL LEDs ON, ILED = 25.6mA
0
-40
-20
0
20
40
60
80
0A
400ns/div
100
TEMPERATURE (°C)
LED LINE TRANSIENT WITH MODE CHANGE
(VIN = 3.8V TO 3.4V TO 3.8V)
1.5x MODE OPERATING
WAVEFORMS (VIN = 3V)
MAX8821 toc09
MAX8821 toc10
AC-COUPLED
100mV/div
VIN
MAX8821 toc11
3.8V
VIN
LED LINE TRANSIENT WITH MODE CHANGE
(VIN = 4.2V TO 3.8V TO 4.2V)
VIN
4.2V
3.4V
0V
2V/div
VNEG
200mA/div
200mA/div
0A
20mA/div
ILED
ALL LEDs ON, ILED = 25.6mA
0A
ILED6
20mA/div
0A
1ms/div
LED STARTUP WAVEFORMS
(VIN = 4V)
LED SHUTDOWN WAVEFORMS
(VIN = 4V)
MAX8821 toc12
IIN
1ms/div
20mA/div
ALL LEDs AT 25.6mA SETTING
0A
1ms/div
LED RAMP-UP
MAX8821 toc14
MAX8821 toc13
AC-COUPLED
50mV/div
VIN
AC-COUPLED
50mV/div
50mA/div
0A
IIN
50mA/div
0A
20mA/div
ILED6
20mA/div
0A
ILED6
ILED6
ALL LEDs AT 25.6mA SETTING 0A
400ns/div
VIN
200mA/div
0A
IIN
IIN
IIN
3.8V
10mA/div
ILED6
0A
10mA/div
ILED5
0A
0A
1ms/div
400ms/div
_______________________________________________________________________________________
9
Typical Operating Characteristics (continued)
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = +25°C, unless otherwise noted.)
CLASS D AMP
TOTAL HARMONIC DISTORTION
vs. OUTPUT POWER
10
THD+N (%)
1
0.1
0.1
VIN = 3.6V
RL = 8Ω
POUT = 100mW
0.01
VIN = 5V
RL = 4Ω
0.01
0.01
10
100
0
0.2
0.4
FREQUENCY (kHz)
-80
0
-120
-140
-140
15
11.95
11.90
11.85
11.80
11.75
AUDIO AMPLIFIER PHASE
vs. FREQUENCY
5
10
15
VRIPPLE = 100mVP-P
AUDIO GAIN = 0dB
RL = 4Ω
CCMREF = 0.1μF
-60
-70
-40
0
15
20
RL = 8Ω
INPUTS AC GROUNDED
-20
AMPLITUDE (dBV)
-30
-40
-50
10
WIDEBAND OUTPUT SPECTRUM
SPREAD-SPECTRUM MODE
-20
PSRR (dB)
-20
5
AUDIO AMPLIFIER PSRR
vs. FREQUENCY
-30
-10
0
FREQUENCY (kHz)
-10
0
20
FREQUENCY (kHz)
0
MAX8821 toc21
10
12.15
12.00
FREQUENCY (kHz)
20
12.20
12.05
0
20
3.0
2.5
12.25
-80
-120
2.0
12.10
-60
-100
1.5
AUDIO AMPLIFIER GAIN
vs. FREQUENCY
-40
-100
10
1.0
GAIN (dB)
-60
5
RL = 8Ω
VBATT = 5V
VOUT = -60dBV
UNWEIGHTED
FFM -1100kHz
-20
-40
0
0.5
OUTPUT POWER (W)
20
AMPLITUDE (dBV)
-20
0
1.0
FIXED-FREQUENCY-MODE OUTPUT
SPECTRUM vs. FREQUENCY
MAX8821 toc18
RL = 8Ω
VBATT = 5V
VOUT = -60dBV
UNWEIGHTED
0
0.8
OUTPUT POWER (W)
SPREAD-SPECTRUM-MODE OUTPUT
SPECTRUM vs. FREQUENCY
20
0.6
MAX8821 toc20
1
MAX8821 toc19
0.1
MAX8821 toc22
0.01
AMPLITUDE (dBV)
1
MAX8821 toc23
0.1
POUT = 350mW
-40
-60
-80
-100
-80
-50
-120
CCMREF = 1μF
-90
-100
-60
0.1
1
10
FREQUENCY (kHz)
10
100
10
THD+N (%)
THD+N (%)
POUT = 25mW
100
MAX8821 toc16
VIN = 3.6V
RL = 8Ω
MAX8821 toc15
1
TOTAL HARMONIC DISTORTION
vs. OUTPUT POWER
MAX8821 toc17
TOTAL HARMONIC DISTORTION
PLUS NOISE vs. FREQUENCY
PHASE (°)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
100
0.1
1
FREQUENCY (kHz)
10
-140
0.001
0.01
0.1
1
FREQUENCY (MHz)
______________________________________________________________________________________
10
100
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
OUTPUT POWER
vs. SUPPLY VOLTAGE
WIDEBAND OUTPUT SPECTRUM
FIXED-FREQUENCY MODE
2.0
OUTPUT POWER (W)
AMPLITUDE (dBV)
-40
-60
-80
MAX8821 toc25
RL = 8Ω
INPUTS AC GROUNDED
-20
2.5
MAX8821 toc24
0
THD+N = 10%
1.5
1.0
THD+N = 1%
-100
0.5
-120
RL = 8Ω
0
0.01
0.1
1
3.1
3.5
3.9
4.3
4.7
SUPPLY VOLTAGE (V)
OUTPUT POWER
vs. SUPPLY VOLTAGE
EFFICIENCY
vs. SUPPLY VOLTAGE
100
MAX8821 toc26
3.5
3.0
THD+N = 10%
1.5
THD+N = 1%
5.5
5.1
5.5
90
2.5
2.0
5.1
RL = 8Ω
95
EFFICIENCY (%)
OUTPUT POWER (W)
2.7
100
10
FREQUENCY (MHz)
MAX8821 toc27
-140
0.001
85
80
RL = 4Ω
75
70
65
1.0
60
0.5
55
RL = 4Ω
0
50
3.1
3.5
3.9
4.3
4.7
5.1
3.1
3.5
3.9
4.3
4.7
SUPPLY VOLTAGE (V)
EFFICIENCY vs. OUTPUT POWER
EFFICIENCY
vs. OUTPUT POWER
100
MAX8821 toc28
RL = 8Ω
80
70
RL = 4Ω
60
50
40
RL = 8Ω
90
80
EFFICIENCY (%)
EFFICIENCY (%)
2.7
SUPPLY VOLTAGE (V)
100
90
5.5
MAX8821 toc29
2.7
70
RL = 4Ω
60
50
40
30
30
20
20
10
VIN = 3.6V
10
VIN = 5V
0
0
0
0.5
1.0
OUTPUT POWER (W)
1.5
2.0
0
1
2
3
4
OUTPUT POWER (W)
______________________________________________________________________________________
11
MAX8821
Typical Operating Characteristics (continued)
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = +25°C, unless otherwise noted.)
DUAL LDOs
STARTUP WAVEFORMS
SHUTDOWN WAVEFORMS
MAX8821 toc30
MAX8821 toc31
1V/div
0V
AIN+ - AIN-
1V/div
AIN+ - AIN-
0V
1V/div
SPK+ - SPK-
0V
1V/div
SPK+ - SPK-
0V
AV = 0dB
AV = 0dB
LDO OUTPUT VOLTAGE
ACCURACY vs. LOAD CURRENT
LDO DROPOUT VOLTAGE
vs. LOAD CURRENT
DROPOUT VOLTAGE (mV)
160
140
LDO1
120
LDO2
100
80
60
40
1
MAX8821 toc33
180
OUTPUT VOLTAGE ACCURACY (%)
MAX8821 toc32
200
VLDO2 = 2.8V
0
-1
-2
VLDO1 = 2.8V
-3
-4
20
-5
0
100
150
200
250
50
100
150
200
LOAD CURRENT (mA)
LOAD CURRENT (mA)
LDO OUTPUT VOLTAGE
vs. TEMPERATURE
LDO PSRR
vs. FREQUENCY
2.90
ILDO1 = 0A
2.85
0
300
ILDO2 = 0A
250
300
0
MAX8821 toc35
50
MAX8821 toc34
0
VIN-RIPPLE = 100mVP-P
-10
-20
-30
2.80
ILDO1 = 100mA
2.75
PSRR (dB)
OUTPUT VOLTAGE (V)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
ILDO2 = 100mA
-40
-50
ILDO2 = 20mA
ILDO1 = 30mA
-60
2.70
-70
2.65
-80
-90
2.60
-40
-15
10
35
TEMPERATURE (°C)
12
60
85
0.01
0.1
1
10
100
FREQUENCY (kHz)
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
LDO LINE TRANSIENT
(VIN3 = 3.6V TO 4.5V)
LDO OUTPUT SPECTRUM
MAX8821 toc37
MAX8821 toc36
0
-20
4.5V
AMPLITUDE (dBV)
-40
3.6V
VIN
-60
VLDO1
AC-COUPLED
10mV/div
VLDO2
AC-COUPLED
10mV/div
-80
-100
-120
-140
ILDO1 = 150mA, ILDO2 = 100mA
-160
0.001
0.01
0.1
1
10
100
200μs/div
1000
FREQUENCY (kHz)
LDO2 LOAD TRANSIENT
LDO1 LOAD TRANSIENT
MAX8821 toc39
MAX8821 toc38
AC-COUPLED
50mV/div
VLDO1
AC-COUPLED
50mV/div
VLDO2
50mA/div
ILDO1
50mA/div
0A
ILDO2
0A
10μs/div
10μs/div
LDO SHUTDOWN RESPONSE
(LDO1, LDO2 UNLOADED)
MAX8821 toc40
VLDO1
1V/div
VLDO2
0V
1V/div
0V
2ms/div
______________________________________________________________________________________
13
MAX8821
Typical Operating Characteristics
(VIN1 = VIN2 = VIN3 = VDD = 3.6V, VAGND = VPGND1 = VPGND2 = 0V, circuit of Figure 2, TA = +25°C, unless otherwise noted.)
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
MAX8821
Pin Description
PIN
14
NAME
FUNCTION
I2C Input Supply Voltage. The VDD supply range is 1.5V to 5.5V. Drive VDD high to enable the I2C
control. Drive VDD low to place the IC into shutdown mode.
1
VDD
2
CMREF
3
AIN+
Noninverting Audio Input
4
AIN-
Inverting Audio Input
5
PGND2
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 I2C interface.
10
LDO1
300mA LDO Output. Bypass LDO1 to AGND with a 2.2µF ceramic capacitor. LDO1 is disabled
through the I2C interface.
11
SCL
I2C Clock Input. Data is read on the rising edge of VSCL.
12
SDA
13
AGND
14
REF
I2C Data Input. Data is read on the rising edge of VSCL..
Analog Ground. Connect AGND to the system ground plane. AGND is also internally connected to
the exposed paddle.
Reference Bypass. Bypass REF with a 0.1µF ceramic capacitor to AGND as close as possible to the IC.
15–20
LED1–
LED6
LED Current Regulators. Current flowing into LED_ is based upon the internal I2C 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
28
IN3
—
EP
Audio Common-Mode Reference Voltage. Bypass CMREF with a 0.1µF ceramic capacitor to AGND
as close as possible to the IC.
Audio Amplifier Power Ground. Connect PGND2 to the system ground plane.
Charge-Pump Power Ground. Connect PGND1 to the system ground plane.
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.
Exposed Paddle. Connect the exposed paddle to AGND directly under the IC. Exposed paddle is
internally connected to AGND.
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
C1N
C2P
MAX8821
C1P
C2N
IN1
INVERTING
CHARGE PUMP
PGND1
NEG
OSCILLATOR
NEG
MAX8821
SELECT
MINIMUM
ADAPTIVE
CURRENT
REGULATORS
LED1
CURRENT
SOURCE
CONTROL
NEG
LED2
CMREF
VDD
I2C INTERFACE AND
LOGIC CONTROL
SDA
NEG
SCL
LED3
NEG
LDO1
LDO1
LED4
IN3
NEG
LDO2
LED5
LDO2
NEG
REF
LED6
REFERENCE
AGND
OSCILLATOR
IN2
IN3
SPK+
AIN+
+
AIN-
-
CLASS D
AMP
PGA
OUTPUT
BUFFER
SPK-
REF
PGND2
PGND2
PGND2
EP
Figure 1. Block Diagram
______________________________________________________________________________________
15
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
C8
1μF
C1P
C9
1μF
C1N
C2P
C2N
INPUT
2.7 TO 5.5V
IN1
C7
2.2μF
NEG
PGND1
C6
1μF
IN2
C3
1μF
LED1
PGND2
IN3
C5
2.2μF
AGND
LED2
MAX8821
REF
INDIVIDUAL
0.1mA TO
25.6mA
DIMMING
LED3
LED4
C4
0.1μF
LED5
LED6
CMREF
C12
0.1μF
LDO1
VDD
LOGIC
CONTROL AND I2C
INTERFACE
LDO2
SDA
C10
2.2μF
DUAL LOWNOISE LDO
C11
1μF
SCL
SPK+
DIFFERENTIAL
AUDIO INPUT
LOUDSPEAKER/EARPIECE
AIN+
SPKAINEP
Figure 2. Typical Application Circuit
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
16
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
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
Current Regulator Switchover
When VIN is 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 (tRAMP)
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 tRAMP/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:
tLED _ RU
t ON _ BLINK ≥
(LED _[4 : 0] + 1)
32
tLED _ RD
t OFF _ BLINK ≥
(LED _[4 : 0] + 1)
32
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.
ILED_ = 25.6mA
tRAMP = tRAMP =
262ms 524ms
tRAMP =
1048ms
tRAMP =
2097ms
tRAMP =
1048ms
tRAMP =
2097ms
ILED_ = 0
Figure 3. Ramp-Up Behavior
ILED_ = 25.6mA
ILED_ = 0
tRAMP =
262ms
tRAMP =
524ms
Figure 4. Ramp-Down Behavior
______________________________________________________________________________________
17
MAX8821
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 I2C interface.
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
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 I2C interface.
The amplifier operates from a single 2.7V to 5.5V supply (VIN3 = VIN2) and features an internally generated
common-mode bias voltage of VIN3 / 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
CIN (Figure 7) are required for single-ended input applications 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.
18
ILED5[4:0]
ILED6[4:0]
0.512s = tOFF_BLINK = 4.098s
64ms = tON_BLINK = 512ms
Figure 5. Blink Timer Behavior
Both comparators reset at a fixed time after the rising
edge of the second comparator trip point, generating a
minimum width pulse tON(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 tON(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
RINT, 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:
f −3dB =
1
2 × π × RINT × CIN
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.
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
MAX8821
tON_BLINK
tOFF_BLINK
tOFF_BLINK
ILED_ = LED_ [4.0]
ILED_ = 0mA
t = tLED_RU/32
t = tLED_RD/32
Figure 6. Combining Ramp Function and Blink Timer (Tables 10 and 11)
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.
RINT
CIN
MAX8821
MONO
CLASS D
AUDIO AMP
AUDIO
INPUTS
CIN
EARPIECE/
LOUDSPEAKER
RINT
Figure 7. Optional Input Capacitors
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
VDD low. 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 VIN_ drops below the UVLO threshold or VDD is
driven low.
I2C Registers and Control
I2C 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.
______________________________________________________________________________________
19
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
A
C
tLOW B tHIGH
E
D
G
F
H
I
J
K
L
M
SCL
SDA
tSU_DAT
tSU_STA tHD_STA
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
tSU_STO tBUF
tHD_DAT
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
J = ACKNOWLEDGE CLOCKED INTO MASTER
K = ACKNOWLEDGE CLOCK PULSE
L = STOP CONDITION, DATA EXECUTED BY SLAVE
M = NEW START CONDITION
Figure 8. I2C Timing Diagram
Table 1. Register Map
GROUP ADDRESS
(hexadecimal)
TABLE
TYPE
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
NAME
DESCRIPTION
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
20
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
BIT
NAME
B7, B6
N/A, do not use.
B5
CODE
LED1_RP_EN
0
1
LED1 ramp-up/down
disabled.
LED1 ramp-up/down
enabled.
0.1mA
B5
NAME
CODE
DESCRIPTION
N/A, do not use.
LED2_RP_EN
0
1
00000
LED2 ramp-up/down
disabled.
LED2 ramp-up/down
enabled.
0.1mA
0.2mA
00001
0.2mA
00010
0.3mA
00010
0.3mA
0.4mA
00011
0.4mA
00100
0.5mA
00100
0.5mA
00101
0.6mA
00101
0.6mA
0.7mA
00110
0.7mA
00111
0.8mA
00111
0.8mA
01000
1.0mA
01000
1.0mA
01001
1.2mA
01001
1.2mA
01010
1.4mA
01010
1.4mA
01011
1.6mA
01011
1.6mA
01100
2.0mA
01100
2.0mA
01101
2.4mA
01101
2.4mA
01110
2.8mA
01110
2.8mA
01111
3.2mA
01111
3.2mA
10000
4.0mA
10000
4.0mA
10001
4.8mA
10001
4.8mA
10010
5.6mA
10010
5.6mA
10011
6.4mA
10011
6.4mA
10100
8.0mA
10100
8.0mA
10101
9.6mA
10101
9.6mA
10110
11.2mA
10110
11.2mA
10111
12.8mA
10111
12.8mA
11000
14.4mA
11000
14.4mA
11001
16.0mA
11001
16.0mA
11010
17.6mA
11010
17.6mA
11011
19.2mA
11011
19.2mA
11100
20.8mA
11100
20.8mA
11101
22.4mA
11101
22.4mA
11110
24.0mA
11110
24.0mA
11111
25.6mA
11111
25.6mA
00110
Note: Defaults in bold italics.
BIT
00001
00011
LED1[4:0]
Table 3. LED2_CNTL (Address 0x01)
B7, B6
00000
B4–B0
DESCRIPTION
MAX8821
Table 2. LED1_CNTL (Address 0x00)
B4–B0
LED2[4:0]
Note: Defaults in bold italics.
______________________________________________________________________________________
21
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
Table 4. LED3_CNTL (Address 0x02)
BIT
B7, B6
B5
NAME
CODE
LED3_RP_EN
LED3[4:0]
Note: Defaults in bold italics.
22
BIT
B7, B6
0
1
00000
B4–B0
DESCRIPTION
N/A, do not use.
Table 5. LED4_CNTL (Address 0x03)
LED3 ramp-up/down
disabled.
LED3 ramp-up/down
enabled.
0.1mA
B5
NAME
CODE
DESCRIPTION
N/A, do not use.
LED4_RP_EN
0
1
00000
LED4 ramp-up/down
disabled.
LED4 ramp-up/down
enabled.
0.1mA
00001
0.2mA
00001
0.2mA
00010
0.3mA
00010
0.3mA
00011
0.4mA
00011
0.4mA
00100
0.5mA
00100
0.5mA
00101
0.6mA
00101
0.6mA
00110
0.7mA
00110
0.7mA
00111
0.8mA
00111
0.8mA
01000
1.0mA
01000
1.0mA
01001
1.2mA
01001
1.2mA
01010
1.4mA
01010
1.4mA
01011
1.6mA
01011
1.6mA
01100
2.0mA
01100
2.0mA
01101
2.4mA
01101
2.4mA
01110
2.8mA
01110
2.8mA
01111
3.2mA
01111
3.2mA
10000
4.0mA
10000
4.0mA
10001
4.8mA
10001
4.8mA
10010
5.6mA
10010
5.6mA
10011
6.4mA
10011
6.4mA
10100
8.0mA
10100
8.0mA
10101
9.6mA
10101
9.6mA
10110
11.2mA
10110
11.2mA
10111
12.8mA
10111
12.8mA
11000
14.4mA
11000
14.4mA
11001
16.0mA
11001
16.0mA
11010
17.6mA
11010
17.6mA
11011
19.2mA
11011
19.2mA
11100
20.8mA
11100
20.8mA
11101
22.4mA
11101
22.4mA
11110
24.0mA
11110
24.0mA
11111
25.6mA
11111
25.6mA
B4–B0
LED4[4:0]
Note: Defaults in bold italics.
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
BIT
B7, B6
B5
NAME
CODE
LED5_RP_EN
0
1
00000
B4–B0
DESCRIPTION
N/A, do not use.
LED5[4:0]
BIT
NAME
B7, B6
N/A, do not use.
B5
LED6_RP_EN
CODE
0
1
00000
DESCRIPTION
LED6 ramp-up/down
disabled.
LED6 ramp-up/down
enabled.
0.1mA
00001
0.2mA
00001
0.2mA
00010
0.3mA
00010
0.3mA
00011
0.4mA
00011
0.4mA
00100
0.5mA
00100
0.5mA
00101
0.6mA
00101
0.6mA
00110
0.7mA
00110
0.7mA
00111
0.8mA
00111
0.8mA
01000
1.0mA
01000
1.0mA
01001
1.2mA
01001
1.2mA
01010
1.4mA
01010
1.4mA
01011
1.6mA
01011
1.6mA
01100
2.0mA
01100
2.0mA
01101
2.4mA
01101
2.4mA
01110
2.8mA
01110
2.8mA
01111
3.2mA
01111
3.2mA
10000
4.0mA
10000
4.0mA
10001
4.8mA
10001
4.8mA
10010
5.6mA
10010
5.6mA
10011
6.4mA
10011
6.4mA
8.0mA
10100
8.0mA
10101
9.6mA
10101
9.6mA
10110
11.2mA
10110
11.2mA
10111
12.8mA
10111
12.8mA
11000
14.4mA
11000
14.4mA
11001
16.0mA
11001
16.0mA
11010
17.6mA
11010
17.6mA
11011
19.2mA
11011
19.2mA
11100
20.8mA
11100
20.8mA
22.4mA
11101
22.4mA
10100
11101
Note: Defaults in bold italics.
LED5 ramp-up/down
disabled.
LED5 ramp-up/down
enabled.
0.1mA
Table 7. LED6_CNTL (Address 0x05)
B4–B0
LED6[4:0]
11110
24.0mA
11110
24.0mA
11111
25.6mA
11111
25.6mA
Note: Defaults in bold italics.
______________________________________________________________________________________
23
MAX8821
Table 6. LED5_CNTL (Address 0x04)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
Table 8. RAMP1_CNTL (Address 0x06)
BIT
NAME
CODE
RAMP TIME (tRAMP) (ms)
B7, B6
LED1_RU[1:0]
LED1 ramp-up control
DESCRIPTION
00
218 x TQPCLK
B5, B4
LED1_RD[1:0]
LED1 ramp-down control
01
219 x TQPCLK
B3, B2
LED2_RU[1:0]
LED2 ramp-up control
10
220 x TQPCLK
B1, B0
LED2_RD[1:0]
LED2 ramp-down control
11
221 x TQPCLK
CODE
RAMP TIME (tRAMP) (ms)
Notes: TQPCLK = 1 / fSW ; defaults in bold italics.
Table 9. RAMP2_CNTL (Address 0x07)
BIT
NAME
DESCRIPTION
B7, B6
LED3_RU[1:0]
LED3 ramp-up control
00
218 x TQPCLK
B5, B4
LED3_RD[1:0]
LED3 ramp-down control
01
219 x TQPCLK
B3, B2
LED4_RU[1:0]
LED4 ramp-up control
10
220 x TQPCLK
B1, B0
LED4_RD[1:0]
LED4 ramp-down control
11
221 x TQPCLK
CODE
RAMP TIME (tRAMP) (ms)
Notes: TQPCLK = 1 / fSW ; defaults in bold italics.
Table 10. RAMP3_CNTL (Address 0x08)
BIT
NAME
DESCRIPTION
B7, B6
LED5_RU[1:0]
LED5 ramp-up control
00
218 x TQPCLK
B5, B4
LED5_RD[1:0]
LED5 ramp-down control
01
219 x TQPCLK
B3, B2
LED6_RU[1:0]
LED6 ramp-up control
10
220 x TQPCLK
B1, B0
LED6_RD[1:0]
LED6 ramp-down control
11
221 x TQPCLK
Notes: TQPCLK = 1 / fSW ; defaults in bold italics.
24
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
BIT
B7, B6
B5, B4
B3, B2
B1, B0
NAME
CODE
BLINK TIME
BIT
00
219 x TQPCLK
B7, B6
01
220 x TQPCLK
10
221 x TQPCLK
11
222 x TQPCLK
00
216 x TQPCLK
01
217 x TQPCLK
10
218 x TQPCLK
11
219 x TQPCLK
0000
1.2V
00
219 x TQPCLK
0001
1.3V
01
220 x TQPCLK
0010
1.5V
10
221 x TQPCLK
0011
1.6V
LED5_OFF_BLINK
LED5_ON_BLINK
LED6_OFF_BLINK
LED6_ON_BLINK
B7
LED1_EN
B6
LED2_EN
B5
LED3_EN
B4
LED4_EN
B3, B2
B1, B0
B4
CODE
DESCRIPTION
N/A, do not use.
LDO1_EN
0
LDO1 is disabled.
1
LDO1 is enabled.
0
Active pulldown enabled
during OFF condition.
1
Active pulldown disabled
during OFF condition.
LDO1_PD
11
222 x TQPCLK
0100
1.8V
216 x TQPCLK
0101
1.9V
01
217 x TQPCLK
0110
2.0V
10
218 x TQPCLK
0111
2.3V
11
219 x TQPCLK
1000
2.5V
1001
2.6V
1010
2.7V
1011
2.8V
1100
2.9V
1101
3.0V
Table 12. LED_EN (Address 0xA)
NAME
B5
NAME
00
Notes: TQPCLK = 1 / fSW ; defaults in bold italics.
BIT
Table 13. LDO1_CNTL (Address 0x0B)
B3–B0
LDO1[3:0]
DESCRIPTION
1110
3.1V
0
LED current source is
disabled.
1111
3.2V
1
LED current source is
enabled.
00
LED current source is
disabled.
01
LED current source is
enabled.
10
LED current source
controlled by blink
timer.
11
N/A, do not use.
CODE
Note: Defaults in bold italics.
LED5_EN[1:0]
LED6_EN[1:0]
Note: Defaults in bold italics.
______________________________________________________________________________________
25
MAX8821
Table 11. BLINK_CNTL (Address 0x09)
MAX8821
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
Table 14. LDO2_CNTL (Address 0x0C)
BIT
B7, B6
B5
B4
B3–B0
NAME
CODE
DESCRIPTION
Table 15. AUDIO_CNTL (Address 0x0D)
BIT
NAME
CODE
DESCRIPTION
0
Audio amplifier and
charge-pump
clocks are not
synchronized.
N/A, do not use.
LDO2_EN
0
LDO2 is disabled.
1
LDO2 is enabled.
0
Active pulldown enabled
during OFF condition.
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
0000
Audio amplifier and
charge-pump clocks
are synchronized.
Charge pump
oscillator clock =
audio clock / 2.
Oscillator frequency
1100kHz, fixedfrequency mode.
Oscillator frequency
1400kHz, fixedfrequency mode.
Oscillator frequency
1250kHz, spreadspectrum mode.
Reserved for future
use.
Class D amplifier is
disabled.
Class D amplifier is
enabled.
-3dB
1111
3.3V
0001
0dB
0010
3dB
0011
6dB
0100
9dB
0101
12dB
0110
15dB
0111
18dB
1000
21dB
B7
SYNC
LDO2_PD
LDO2[3:0]
1
00
01
B6, B5
CLK_CNTL[1:0]
10
11
B4
AMP_EN
Note: Defaults in bold italics.
B3–B0
AUDIO_GAIN[3:0]
0
1
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.
1111
N/A, do not use.
Note: Defaults in bold italics.
26
______________________________________________________________________________________
White LED Charge Pump with Mono Class D
Audio Amp and Dual LDO
BIT
NAME
B7–B3
B2
CODE
DESCRIPTION
N/A, do not use
0
Temperature
derating disabled.
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.
11
N/A, do not use.
TEMP_DR
B1, B0
PUMP_CNTL [1:0]
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.
Note: Defaults in bold italics.
Chip Information
Pin Configuration
NEG
LED6
LED5
LED4
LED3
LED2
LED1
PROCESS: BiCMOS
TOP VIEW
21
20
19
18
17
16
15
C2N 22
14
REF
C1N 23
13
AGND
C2P 24
12
SDA
11
SCL
IN1 26
10
LDO1
PGND1 27
9
LDO2
8
IN2
C1P 25
MAX8821ETI+
EP = EXPOSED PADDLE
2
3
4
5
6
7
AIN+
AIN-
PGND2
SPK-
SPK+
1
VDD
+
CMREF
IN3 28
______________________________________________________________________________________
27
MAX8821
Table 16. PUMP_CNTL (Address 0x0E)
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
28
______________________________________________________________________________________
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.
MAX8821
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.)