Texas Instruments TRF7970A Instruction Manual page 16

TRF7970A
SLOS743K – AUGUST 2011 – REVISED APRIL 2014
6.3.1 Supply Arrangements
Regulator Supply Input: V
The positive supply at V
input sources for three internal regulators with the output voltages V
bypass capacitors for supply noise filtering must be used (per reference schematics).
V must be the highest voltage supplied to the TRF7970A.
IN
RF Power Amplifier Regulator: V
The V (pin 3) regulator is supplying the RF power amplifier. The voltage regulator can be set for
DD_RF
either 5-V or 3-V operation. External bypass capacitors for supply noise filtering must be used (per
reference schematics). When configured for 5-V manual-operation, the V
from 4.3 V to 5 V in 100-mV steps. In 3-V manual-operation, the output can be programmed from 2.7 V to
3.4 V in 100-mV steps. The maximum output current capability for 5-V operation is 150 mA and for 3-V
operation is 100 mA.
Analog Supply Regulator: V
Regulator V (pin 1) supplies the analog circuits of the device. The output voltage setting depends on
DD_A
the input voltage and can be set for 5-V and 3-V operation. When configured for 5-V manual-operation,
the output voltage is fixed at 3.4 V. External bypass capacitors for supply noise filtering must be used (per
reference schematics). When configured for 3-V manual-operation, the V
to 3.4 V in 100-mV steps (see
Note: the configuration of V
output current should not exceed 20 mA.
Digital Supply Regulator: V
The digital supply regulator V
can also be used to supply external electronics within the reader system. When configured for 3-V
operation, the output voltage can be set from 2.7 to 3.4 V in 100-mV steps. External bypass capacitors for
supply noise filtering must be used (per reference schematics).
Note: the configuration of the V
output current should not exceed 20 mA.
The RF power amplifier regulator (V
(V ) can be configured to operate in either automatic or manual mode described in
DD_X
automatic regulator setting mode ensures an optimal compromise between PSRR and the highest
possible supply voltage to ensure maximum RF power output.
By default, the regulators are set in automatic regulator setting mode. In this mode, the regulators are
automatically set every time the system is activated by setting EN input High or each time the automatic
regulator setting bit, B7 in register 0x0B is set to a 1. The action is started on the 0 to 1 transition. This
means that, if the user wants to re-run the automatic setting from a state in which the automatic setting bit
is already high, the automatic setting bit (B7 in register 0x0B) should be changed: 1-0-1.
By default, the regulator setting algorithm sets the regulator outputs to a "Delta Voltage" of 250 mV below
V , but not higher than 5 V for V
IN
regulator mode can be increased up to 400 mV (for details, see bits B0 to B2 in register 0x0B).
16 Detailed Description
IN
(pin 2) has an input voltage range of 2.7 V to 5.5 V. V
IN
DD_RF
DD_A
Table 6-2).
and V regulators are not independent from each other. The V
DD_A DD_X
DD_X
(pin 32) provides the power for the internal digital building blocks and
DD_X
and V regulators are not independent from each other. The V
DD_A DD_X
), analog supply regulator (V
DD_RF
and 3.4 V for V
DD_RF
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DD_RF
NOTE
DD_RF
DD_A
DD_A
and V . The "Delta Voltage" in automatic
DD_A DD_A
Copyright © 2011–2014, Texas Instruments Incorporated
TRF7970A
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provides the supply
IN
, V , and V . External
DD_A DD_X
output voltage can be set
output can be set from 2.7 V
) and digital supply regulator
Section 6.3.2. The
DD_A
DD_X