ISL54211_14 Datasheet, PDF (10/19 Pages) Intersil Corporation – MP3/USB 2.0 High Speed Switch with Negative Signal Handling/Click and Pop Suppression

ISL54211
high-speed USB differential data signals with minimal edge
and phase distortion.
The ISL54211 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. See “Typical Application Block
Diagrams” on page 9 regarding functionality.
The ISL54211 has a single logic control pin (IN) that selects
between the audio and the USB switches. This pin can be
driven low or high to switch between the audio CODEC
drivers and USB transceiver of the MP3 player or cellphone.
The ISL54211 also contains a logic control pin (CTRL) that
when driven low while IN 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 “Typical Performance Curves”
beginning on page 12).
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 switches have click and pop circuitry on the L
and R side that is activated when the IN voltage is ≤ 0.5V or
floating and the CTRL voltage ≤ to 0.5V or floating. The
ISL54211 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 IN
voltage is ≤ 0.5V or floating and the CTRL voltage ≥ to 1.4V.
USB Switches
The two USB switches (D+, D-) are 5.5Ω bidirectional
switches that were specifically designed to pass high-speed
USB differential signals typically in the range of 0V to
400mV. The switches have low capacitance and high
bandwidth to pass USB high-speed signals (480Mbps) with
minimum edge and phase distortion to meet USB 2.0 signal
quality specifications. See Figure 20 for High-speed Eye
Pattern taken with the switch in the signal path.
These switches can also swing rail to rail and pass USB
full-speed signals (12Mbps) with minimal distortion. See
Figure 21 for Full-speed Eye Pattern taken with the switch in
the signal path.
The maximum signal range for the USB switches is from
-1.5V to V_DD. The signal voltage at D- and D+ should not be
allow to exceed the V_DD voltage rail or go below ground by
more than -1.5V.
The USB switches are active (turned ON) whenever the IN
voltage is ≥ to 1.4V.
ISL54211 Operation
The following sections discuss using the ISL54211 in the
“Typical Application Block Diagrams” on page 9.
VDD SUPPLY
The DC power supply connected at VDD (pin 10 for µTQFN,
pin 1 for TDFN) provides the required bias voltage for proper
switch operation. The part can operate with a supply voltage
in the range of 2.7V to 5.0V.
In a typical USB/Audio application for portable battery
powered devices, the V_DD voltage will come from a battery
or an LDO and be in the range of 2.7V to 4.3V. For best
possible USB full-speed operation (12Mbps), it is
recommended that the V_DD voltage be ≥2.7V in order to get
a USB data signal level above 2.7V.
LOGIC CONTROL
The state of the ISL54211 device is determined by the
voltage at the IN pin (pin 1 for µTQFN; pin 2 for TDFN) and
the CTRL pin (pin 9 for µTQFN, pin 10 for TDFN). These
logic pins are 1.8V logic compatible when V_DD is in the
range of 2.7V to 3.6V and can be controlled by a standard
µprocessor. The part has three states or modes of operation:
Audio Mode; USB Mode; and Mute Mode. Refer to “Truth
Table” on page 2.
The IN pin and CTRL pin are internally pulled low through
4MΩ resistors to ground and can be left floating or tri-stated
by the µprocessor. The CTRL control pin is only active when
IN is logic “0”.
Logic Control Voltage Levels
IN = Logic “0” (Low) when ≤ 0.5V or Floating.
IN = Logic “1” (High) when ≥ 1.4V
10
FN6662.1
August 25, 2008