TCM4300 Datasheet, PDF (39/69 Pages) Texas Instruments – Advanced RF Cellular Telephone Interface Circuit (ARCTIC )

SQRC shaping filter with a roll-off rate of α = 0.35 and converted to sampled analog form by two 9-bit DACs.
The output of the DAC is then filtered by a continuous-time resistance-capacitance (RC) filter.
The TCM4300 generates a power amplifier (PA) control signal, PAEN, to enable the power supply for the
PA. The start and stop times of the TDM burst are controlled by writing to a single bit, TXGO, in the DSP
DStatCtrl register.
In the analog mode (MODE = 0), the DSP writes 8-bit I and Q samples into the TXI and TXQ data registers
at a 40-ksps rate. These writes are timed by the SINT interrupt signal. The samples are fed to a low-pass
filter before D / A conversion. In the transmit analog mode, PAEN is always set to 1.
The transmit section provides differential I and Q outputs (see Table 4-5) for both analog and digital modes.
The differential dc offset for the TXI and TXQ outputs can be independently adjusted using the transmit offset
registers.
Table 4–5. Transmit (TX) I and Q Channel Outputs
PARAMETER
MIN TYP MAX UNIT
Peak output voltage full scale, centered at VCM
Differential
2.24
Vp
Single ended
1.12
Differential
1.5
Nominal output-level (constellation radius) centered at VCM
V
Single ended
0.75
Low-level drift
± 200
PPM/°C
Transmit error vector magnitude (EVM)
3% 4%
Transmit DACs I and Q resolution
8
bits
S/(N+D) ratio at differential outputs
48
52
dB
Gain error (I or Q channel)
Gain mismatch between I and Q
± 8% ± 12%
± 0.3 dB
Gain sampling mismatch between I and Q
20
ns
Zero code error, I to Q, with respect to other channel (differential or single
ended). (See Figure 4–1).
± 1.1 LSB
Residual offset error, I or Q, with respect to VCM. (See Note 5 and
Figure 4–1).
10
kΩ
Load impedance, between P and N terminals
10
kΩ
Transmit offset DACs I and Q resolution
6
bits
Transmit offset DACs I and Q average step size
5.0 mV
Transmit offset DACs differential nonlinearity
Transmit offset DACs integral nonlinearity
± 1.1 LSB
± 1.1 LSB
NOTES: 5. The residual (uncorrectable) offset error is the residual offset error I or Q, with respect to VCM, which cannot
be eliminated using the transmit offset DACs. The proper correction algorithm must be implemented to
minimize the I and Q offset.
TXI
VCM
TXQ
MAX Residual
Offset Error TXI
MAX Residual
Offset Error TXQ
0.55 LSB
1.1 LSB
0.55 LSB
MAX Zero Code
Error, I to Q
Figure 4–1. Residual (Uncorrectable) Offset Error and Zero Code Error, I to Q
4–4