Tripath Technology, Inc. - Technical Information
RS and ROCR are in Ω
V
TOC = Over-current sense threshold voltage (See Electrical Characteristics Table)
= 1.0V typically
IBIAS = 20uA
For example, to set an ISC of 7A, ROCR = 30.1kΩ and RS will be 10mΩ.
As high-wattage resistors are usually only available in a few low-resistance values (10mΩ, 25mΩ
and 50mΩ), ROCR can be used to adjust for a particular over-current threshold using one of these
values for RS.
It should be noted that the addition of the bulk CHBR capacitor shown in the Application / Test
Diagram will increase the ISC level. Thus, it will be larger than the theoretical value shown above.
Once the designer has settled on a layout and specific CHBR value, the system ISC trip point can
be adjusted by increasing the ROCR value. The ROCR should be increased to a level that allows
expected range of loads to be driven well into clipping without current limiting while still protecting
the output MOSFETs in case of a short circuit condition.
Auto Recovery Circuit for Overcurrent Fault Condition
If an overcurrent fault condition occurs the HMUTE pin (pin 8 of the TC2001) will be latched high
and the amplifier will be muted. The amplifier will remain muted until the MUTE pin (pin 24 of the
TC2001) is toggled high and then low or the power supplies are turned off and then on again.
The circuit shown below in Figure 4 is a circuit that will detect if HMUTE is high and then toggle
the mute pin high and then low, thus resetting the amplifier. The LED, D1 will turn on when
HMUTE is high. The reset time has been set for approximately 2.5 seconds. The duration of the
reset time is controlled by the RC time constant set by R306 and C311. To increase the reset,
time increase the value of C311. To reduce the reset time, reduce the value of C311. Please
note that this circuit is optional and is not included on the RB-TK2150 evaluation boards.
V5
R309
1kΩ , 5%
D1
LED
R311
R306
510kΩ , 5%
R307
10kΩ , 5%
R308
10kΩ , 5%
Q305
2N3906
1kΩ , 5%
R311
1kΩ , 5%
MUTE
Pin 24
C311
10uF, NP
Q302
2N3904
Q303
2N7002
R311
1kΩ , 5%
Jumper
HMUTE
Pin 8
Q304
2N3904
R310
1kΩ , 5%
remove jumper to
enable mute
AGND
Figure 4: Overcurrent Autorecovery Circuit
Over- and Under-Voltage Protection
The TC2001 senses the power rails through external resistor networks connected to VNNSENSE
and VPPSENSE. The over- and under-voltage limits are determined by the values of the resistors
in the networks, as described in the table “Test/Application Circuit Component Values”. If the
supply voltage falls outside the upper and lower limits determined by the resistor networks, the
TC2001 shuts off the output stages of the amplifiers. The removal of the over-voltage or under-
voltage condition returns the TK2150 to normal operation. Please note that trip points specified in
the Electrical Characteristics table are at 25°C and may change over temperature.
The TC2001 has built-in over and under voltage protection for both the VPP and VNN supply
rails. The nominal operating voltage will typically be chosen as the supply “center point.” This
allows the supply voltage to fluctuate, both above and below, the nominal supply voltage.
22
TK2150 – Rev. 1.0/12.02
TRIPATH [ TRIPATH TECHNOLOGY INC. ]
