TCM4300IPZ datasheet(39/69 Pages) TI1

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4–4

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

Peak output voltage full scale, centered at VCM

Single ended

1.12

Nominal output level (constellation radius) centered at VCM

Differential

1.5

Nominal output-level (constellation radius) centered at VCM

Single ended

0.75

Low-level drift

±200

PPM/

°C

Transmit error vector magnitude (EVM)

Transmit DACs I and Q resolution

bits

S/(N+D) ratio at differential outputs

Gain error (I or Q channel)

±8% ±12%

Gain mismatch between I and Q

±0.3

Gain sampling mismatch between I and Q

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).

Ω

Load impedance, between P and N terminals

Ω

Transmit offset DACs I and Q resolution

bits

Transmit offset DACs I and Q average step size

5.0

Transmit offset DACs differential nonlinearity

±1.1

LSB

Transmit offset DACs integral nonlinearity

±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.

MAX Residual

Offset Error TXI

0.55 LSB

MAX Residual

Offset Error TXQ

0.55 LSB

1.1 LSB

MAX Zero Code

Error, I to Q

TXI

TXQ

VCM

Figure 4–1. Residual (Uncorrectable) Offset Error and Zero Code Error, I to Q

TCM4300IPZ Datasheet(PDF) 39 Page - Texas Instruments

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