MAX4295 Maxim, MAX4295 Datasheet - Page 11

• Manufacturer Part Number: MAX4295
• Description: Mono/Stereo 2W Switch-Mode (Class-D) Audio Power Amplifiers
• Manufacturer: Maxim

H-bridge. The switches work in pairs to reverse the
polarity of the signal in the load. Break-before-make
switching of the H-bridge MOSFETs by the driver circuit
keeps supply current glitches and crowbar current in
the MOSFETs at a low level. The output swing of the H-
bridge is a direct function of the supply voltage.
Varying the oscillator swing in proportion to the supply
voltage maintains constant gain with varying supply
voltage.
FS1 and FS2 program the oscillator to a frequency of
125kHz, 250kHz, 500kHz, and 1MHz. The sawtooth
oscillator swings between GND and 0.6
input signal is typically AC-coupled to the internal input
op amp, whose gain can be controlled through external
feedback components. The common-mode voltage of
the input amplifier is 0.3
ated from the same resistive divider used to generate
the 0.6
A current-limiting circuit in the H-bridge monitors the
current in the H-bridge transistors and disables the H-
bridge if the current in any of the H-bridge transistors
exceeds 1A. The H-bridge is enabled after a period of
Figure 1a. MAX4295 Functional Diagram
✕
IN
AOUT
V
CSS
CC
0.3
FS2
FS1
(VCM)
✕
reference for the PWM oscillator.
V
SS
CC
______________________________________________________________________________________
Mono/Stereo 2W Switch-Mode (Class-D)
POWER MANAGEMENT
✕
AND PROTECTION
V
CC
PWM
OSC
and is internally gener-
Current Limit
✕
V
GND
V
CC
CC
. The
Audio Power Amplifiers
100µs. A continuous short circuit at the output results in
a pulsating output.
Thermal overload protection limits total power dissipa-
tion in the MAX4295/MAX4297. When the junction tem-
perature exceeds +145°C, the thermal detection
disables the H-bridge transistors. The H-bridge transis-
tors are enabled after the IC’s junction temperature
cools by 10°C. This results in a pulsating output under
continuous thermal overload conditions. Junction tem-
perature does not exceed the thermal overload trip
point in normal operation, but only in the event of fault
conditions, such as when the H-bridge outputs are
short circuited.
At low supply voltages, the MOSFETs in the H-bridge
may have inadequate gate drive thus dissipating
excessive power. The undervoltage lockout circuit pre-
vents the device from operating at supply voltages
below +2.2V.
Thermal Overload Protection
Undervoltage Lockout
DRIVE
DRIVE
GATE
GATE
PGND
PGND
PV
PV
CC
CC
OUT-
OUT+
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