ADP1046-100-EVALZ AD [Analog Devices], ADP1046-100-EVALZ Datasheet - Page 15

• Manufacturer Part Number: ADP1046-100-EVALZ
• Description: Digital Controller for Isolated
• Manufacturer: AD [Analog Devices]

Data Sheet
THEORY OF OPERATION
CURRENT SENSE
The
These inputs sense, protect, and control the primary input
current, secondary output current, and the share bus
information. They can be calibrated to reduce errors due to
external components.
CS1 Operation (CS1)
CS1 is typically used for the monitoring and protection of
the primary side current, which is commonly sensed using a
current transformer (CT). The input signal at the CS1 pin is fed
into an ADC for current monitoring. The range of the ADC is
0 V to 1.4 V. The input signal is also fed into a comparator for
pulse-by-pulse OCP protection. The typical configuration for
the CS1 current sense is shown in Figure 13.
OUTA
OUTB
The CS1 ADC is used to measure the average value of the
primary current; the reading is averaged every 2.62 ms in an
asynchronous fashion to make fault decisions. The
also writes the 12-bit CS1 reading every 10 ms to Register 0x13.
The fast OCP comparator is used to limit the instantaneous
primary current within each switching cycle and has a nominal
threshold of 1.2 V.
Various thresholds and limits can be set for CS1, as described in
the Current Sense and Current Limit Registers section.
CS2 Operation (CS2+, CS2−)
CS2+ and CS2− are differential inputs used for the monitoring
and protection of the secondary side current. The full-scale
range of the CS2 ADC is programmable to 60 mV or 120 mV.
The differential inputs are fed into an ADC through a pair of
external resistors that provide the necessary level shifting. The
device pins, CS2+ and CS2−, are internally regulated to approxi-
mately 1 V by internal current sources.
V
IN
ADP1046
OUTC
OUTD
I = 10A
Figure 13. Current Sense 1 (CS1) Operation
has two current sense inputs: CS1 and CS2±.
1:100
1kΩ
10Ω
1V
I = 100mA
V
CS1
REF
ADC
ADP1046
12 BITS
FAST
OCP
Rev. 0 | Page 15 of 96
When using low-side current sensing, the current sources are
200 μA; therefore, the required resistor value is 1 V/200 μA = 5 kΩ.
When using high-side current sensing, the current sources are
2 mA; therefore, the resistor value required is (V
In the case of V
Typical configurations are shown in Figure 14 and Figure 15.
Various thresholds and limits can be set for CS2±, such as OCP.
These thresholds and limits are described in the Current Sense
and Current Limit Registers section.
When not in use, the CS2+ and CS2− inputs should both be
connected directly to PGND, and CS2± should be set to high-
side current sense mode (Register 0x27[2] = 1).
The CS2 ADC is used to measure the CS2 current; the reading
is averaged every 2.62 ms in an asynchronous fashion. This
averaged reading is used to make fault decisions, such as the
CS2 OCP fault. The
reading every 10 ms to Register 0x18.
Figure 15. Low-Side Resistive Current Sense (Recommended)
Figure 14. High-Side Resistive Current Sense
200µA
OUT
CS2–
5kΩ
= 12 V, the required resistor value is 5.5 kΩ.
2mA
5.5kΩ
CS2+
ADP1046
1V
I
1V
I
5kΩ
CS2+
200µA
5.5kΩ
CS2–
also writes the 12-bit CS2
2mA
12V
ADC
ADC
12 BITS
OUT
ADP1046
12 BITS
− 1 V)/2 mA.