ISL54210_14 Datasheet, PDF (11/21 Pages) Intersil Corporation – MP3/USB 2.0 High Speed Switch with Negative Signal Handling/Click and Pop Suppression

ISL54210
Typical Application Block Diagram
3.3V
V_BUS
V_BUS
V_DD
ISL54210
LOGIC CONTROL
4MΩ
CTRL
4MΩ
D-
COM -
200kΩ
D+
COM +
200kΩ
CLICK
R
AND
L
POP
GND
µCONTROLLER
USB
HIGH-SPEED
TRANSCEIVER
AUDIO
CODEC
Detailed Description
The ISL54210 device is a dual single pole/double throw
(SPDT) analog switch that operates from a single DC
power supply in the range of 2.7V to 3.6V. It was
designed to function as a dual 2-to-1 multiplexer to
select between USB differential data signals and audio L
and R stereo signals. It comes in tiny µTQFN and TDFN
packages for use in MP3 players, PDAs, cellphones, and
other personal media players.
The part consists of two 2.5Ω audio switches and two
5.5Ω USB switches. The audio switches can accept
signals that swing below ground. They were designed to
pass audio left and right stereo signals, that are ground
referenced, with minimal distortion. The USB switches
were designed to pass high-speed USB differential data
signals with minimal edge and phase distortion.
The ISL54210 was specifically designed for MP3 players,
personal media players and cellphone applications that
need to combine the audio headphone jack and the USB
data connector into a single shared connector, thereby
saving space and component cost. A “Typical Application
Block Diagram” of this functionality is shown on page 11.
The ISL54210 incorporates circuitry for the detection of
the USB V_BUS voltage, which is used to switch between
the audio CODEC drivers and USB transceiver of the MP3
player or cellphone. The ISL54210 contains a logic
control pin (CTRL) that when driven low while V_BUS is
low, opens all switches and activates the audio click and
pop circuitry.
A detailed description of the two types of switches are
provided in the following sections. In a typical
application, the USB transmission and audio playback are
intended to be mutually exclusive operations.
Audio Switches
The two audio switches (L, R) are 2.5Ω switches that can
pass signals that swing below ground. Crosstalk between
the audio switches is <-100dB over the audio band.
These switches have excellent off-isolation >105dB over
the audio band with a 32Ω load.
Over a signal range of ±1V (0.707V_RMS) with
V_DD > 2.7V, these switches have an extremely low r_ON
resistance variation. They can pass ground referenced
audio signals with very low distortion (<0.06% THD+N)
when delivering 15.6mW into a 32Ω headphone speaker
load. See Figures 16, 17, 18, and 19 THD+N in “Typical
Performance Curves” beginning on page 14.
The audio drivers should be connected at the L and R
side of the switch (pins 5 and 6 for µTQFN, pins 6 and 7
for TDFN) and the speaker loads should be connected at
the COM side of the switch (pins 2 and 3 for µTQFN, pins
3 and 4 for TDFN).
The audio switches have click and pop circuitry on the L
and R side that is activated when the V_BUS voltage is ≤
V_DD + 0.2V or floating and the CTRL voltage ≤ to 0.5V or
floating. The ISL54210 should be put in this mode before
powering down or powering up of the audio CODEC
drivers. In this mode, both the audio and USB in-line
switches will be OFF and the audio click and pop circuitry
will be ON. The high off-isolation of the audio switches
along with the click and pop circuitry will isolate the
transients generated during power-up and power-down
of the audio CODECs from getting through to the
headphones, thus eliminating click and pop noise in the
headphones.
The audio switches are active (turned ON) whenever the
V_BUS voltage is ≤ V_DD + 0.2V or floating and the CTRL
voltage ≥ to 1.4V.
11
FN6661.2
March 18, 2010