AMC7834 Datasheet, PDF (81/93 Pages) Texas Instruments – AMC7834 12-Bit Integrated Power-Amplifier Monitor and Control System with Temperature, Current and Voltage Supervision Capabilities

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AMC7834
SLAS972B – NOVEMBER 2014 – REVISED MARCH 2016
8.2.2.4 Current Sensing Applications
The AMC7834 device also features four high-side current-sense amplifiers that support common-mode voltages
from 4 to 60 V and a full-scale sense voltage of 0 to 200 mV. In applications that require current sensing across
a power amplifier, the SENSE± differential inputs connect across a resistor to sense small differential voltage that
is proportional to current across the PA as shown in Figure 107. The current-sense conversion results are stored
in the Current sense data registers. The current sensors are also configurable as closed-loop drain current
controllers. See the Current Sensors section for details.
Figure 107 shows a method of separating the drain voltage from the power amplifier with a series PMOS
transistor. The activation of the PMOS connects the PAV_DD voltage supply to the drain pin of the power amplifier.
The PMOS is driven with a voltage divider that swings from PAV_DD to PAV_DD(R2 / [R1 + R2]). The NMOS shown
in Figure 107 is connected to the PA_ON output which controls the state of the PMOS transistor.
PA Drain Voltage
SENSE1+
R1
R(SENSE)
ûV = IDS u R(SENSE)
SENSE1±
PMOS
R2
IDS
PA ON
NMOS
DAC Voltage
Gate
Drain
Source
Power Amplifier
Figure 107. Current Sense (SENSE) Connections With PMOS ON and OFF
8.2.3 Application Performance Curve
50
100pF
40
200pF
30
1nF
10nF
20
10
0
-10
-20
-30
-40
-50
0
5
10
15
20
25
30
Time ( s)
C023
Code 0x000 to 0xFFF to within 0.5% of final value
Figure 108. DAC Settling Time
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