Datasheet
MAX4999
USB 2.0 Hi-Speed Differential
8:1 Multiplexer
8 _______________________________________________________________________________________
Applications Information
Increasing USB Channels
The MAX4999 features an enable input that allows two
MAX4999s to be connected, allowing multiplexing
between 16 USB channels. Figure 4 shows the typical
application with a single USB common terminal multi-
plexed to eight channels (8:1). See the Eye Diagram -
Single graph in the
Typical Operating Characteristics
.
Figure 5 shows two MAX4999 devices configured with
the USB common terminal multiplexed to 16 USB chan-
nels (16:1). See the Eye Diagram - Double graph in the
Typical Operating Characteristics
. The MAX4999 was
designed to be symmetrical so that the two common
ports may be wired in parallel with very short wiring to
create a 16:1 configuration. When operating in 16:1 con-
figuration, interchange COM0 and COM1 on the second
device to reverse the D+ and D- pins. This minimizes
vias and crossovers (Figure 5).
USB Switching
The MAX4999 analog multiplexers are fully compliant
with the USB 2.0 specification. The low on-resistance
and low on-capacitance of the MAX4999 make it ideal
for high-performance switching applications.
Board Layout
Hi-Speed switches require proper layout and design pro-
cedures for optimum performance. Keep design-con-
trolled impedance PCB traces as short as possible.
Ensure that high-quality bypass ceramic capacitors
(X7R, X5R or better) are placed as close to the device as
possible and use large ground planes where possible.
V
CC
GND
C0
EN
C1
C2
CONTROL
LOGIC
CHARGE
PUMP
MAX4999
COM1
MUX
D0 _1
D1 _1
D2 _1
D3 _1
D4 _1
D5 _1
D6 _1
D7 _1
COM0
MUX
D0 _0
D1 _0
D2 _0
D3 _0
D4 _0
D5 _0
D6 _0
D7 _0
Functional Diagram/Truth Table
X = DON’T CARE
MAX4999
EN C2 C1 C0 FUNCTION
1 0 0 0 COM_→D0_ _
1 0 0 1 COM_→D1_ _
1 0 1 0 COM_→D2_ _
1 0 1 1 COM_→D3_ _
1 1 0 0 COM_→D4_ _
1 1 0 1 COM_→D5_ _
1 1 1 0 COM_→D6_ _
1 1 1 1 COM_→D7_ _
0XXX
STANDBY MODE.
ALL SWITCHES IN HIGH-
IMPEDANCE STATE.
CHARGE PUMP IS OFF.