MAX9768EVKIT+ Maxim Integrated Products, MAX9768EVKIT+ Datasheet - Page 14

• Manufacturer Part Number: MAX9768EVKIT+
• Description: EVALUATION KIT FOR MAX9768
• Manufacturer: Maxim Integrated Products

Specifications of MAX9768EVKIT+

• Amplifier Type: Class D
• Output Type: 1-Channel (Mono)
• Max Output Power X Channels @ Load: 10W x 1 @ 8 Ohm
• Voltage - Supply: 4.5 V ~ 14 V
• Operating Temperature: -40°C ~ 85°C
• Board Type: Fully Populated
• Utilized Ic / Part: MAX9768
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Table 2. Modulation Scheme Selection In Analog Mode
10W Mono Class D Speaker
Amplifier with Volume Control
The MAX9768 features two output modulation
schemes: filterless modulation or classic PWM, selec-
table through SCLK when the device is in analog mode
(ADDR2 and ADDR1 = GND, Table 2) or through the
I
lation scheme eliminates the LC filter required by tradi-
tional Class D amplifiers, reducing component count,
conserving board space and system cost. Although the
MAX9768 meets FCC and other EMI limits with a low-
cost ferrite bead filter, many applications still may want
to use a full LC-filtered output. If using a full LC filter,
the performance is best with the MAX9768 configured
for classic PWM output.
Switching between schemes while in normal operating
mode with the I
pop protected. To have click-and-pop protection when
switching between output schemes, the device must
enter shutdown mode and be configured to the new out-
put scheme before the startup sequence is terminated.
The startup time for the MAX9768 is typically 220ms.
The startup time for the MAX9768B is typically 15ms.
Efficiency of a Class D amplifier is due to the switching
operation of the output stage transistors. In a Class D
amplifier, the output transistors act as current-steering
switches and consume negligible additional power.
Any power loss associated with the Class D output
stage is mostly due to the I
resistance, and quiescent-current overhead.
The theoretical best efficiency of a linear amplifier is
78%, however, that efficiency is only exhibited at peak
output power. Under normal operating levels (typical
music reproduction levels), efficiency falls below 30%,
whereas the MAX9768 still exhibits > 80% efficiencies
under the same conditions (Figure 2).
14
2
C interface (Table 7). Maxim’s unique, filterless modu-
ADDR2
______________________________________________________________________________________
0
0
Filterless Modulation/PWM Modulation
2
ADDR1
C interface, the output is not click-and-
0
0
2
R loss of the MOSFET on-
Analog Volume Control
Analog Volume Control
SDA/VOL
Efficiency
When the output current exceeds the soft current limit,
2A (typ), the MAX9768 enters a cycle-by-cycle current-
limit mode. In soft current-limit mode, the output is
clipped at 2A. When the output decreases so the out-
put current falls below 2A, normal operation resumes.
The effect of soft current limiting is a slight increase in
distortion. Most applications will not enter soft current-
limit mode unless the speaker or filter creates imped-
ance nulls below 8Ω.
Figure 2. MAX9768 Efficiency vs. Class AB Efficiency
SCLK
100
0
1
90
80
70
60
50
40
30
20
10
0
0
MAX9768
EFFICIENCY vs. OUTPUT POWER
2
CLASS AB
OUTPUT POWER (W)
4
Classic PWM (50% Duty Cycle)
6
Filterless Modulation
Soft Current Limit
PV
f
R
IN
FUNCTION
L
DD
8
= 1kHz
= 8Ω
= 12V
10