STCD1020_10 Datasheet, PDF (12/40 Pages) STMicroelectronics – Multichannel clock distribution circuit

Application information
4
Application information
STCD1020, STCD1030, STCD1040
4.1
Typical applications
The STCD1020, STCD1030 and STCD1040 distribute a source clock (for example, from
VCTCXO) to 2, 3 or 4 channel outputs. The typical application circuits using STCD1040 are
shown in Figure 7 and Figure 8 below.
In Figure 7, the clock from VCTCXO is distributed to the TD-SCDMA transmitter and
receiver and GSM transceiver separately.
In Figure 8, the buffer #4 output is fed into the Bluetooth system. In order to allow minimum
power consumption, a Bluetooth system always has a clock request feature. If the Bluetooth
system does not require the clock, the clock request will disable the clock output.
The enable pins can also be connected to logic high to let the channel output always on. If
the channels of STCD1020, STCD1030 and STCD1040 are not used in the application, the
enable pins of the channels should be connected to ground on PCB.
Figure 7. Typical application circuit using STCD1040 for RF ends of TD-
SCDMA/GSM dual-mode mobile phone
VCTCXO
VCC
VCC
STCD1040 ^EN4
CLK4
EN3
MCLK
CLK3
EN2
CLK2
EN1
GND ^CLK1
Mode
selection
TD-SCDMA
transmitter
TD-SCDMA
receiver
GSM
transceiver
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Doc ID 13823 Rev 6