AD5560 Analog Devices, Inc., AD5560 Datasheet - Page 34

• Manufacturer Part Number: AD5560
• Description: 1.2 A Programmable Device Power Supply With Integrated 16-bit Level Setting Dacs
• Manufacturer: Analog Devices, Inc.

AD5560
FORCE AMPLIFIER STABILITY
There are three modes for configuring the force amplifier: safe
mode, autocompensation mode, and manual compensation mode.
Manual compensation mode has highest priority, followed by safe
mode, then autocompensation mode.
Safe Mode
Selected through Compensation Register 1 (see Table 20), this
mode guarantees stability of the force amplifier under all
conditions. Where the load is unknown, this mode is useful but
results in a slow response. This is the power-on default of the
AD5560.
Autocompensation Mode
Using this mode, the user inputs the C
the AD5560 decides the most appropriate compensation
scheme for these load conditions. The compensation chosen
is for an optimum tradeoff between ac response and stability.
Manual Compensation Mode
This mode allows access to all of the internal programmable
parameters to configure poles/zeros, which affect the dynamic
performance of the loop. These variables are outlined in
Table 12 and Table 13.
Figure 55 shows more details of the force amplifier block.
500Ω TO
1.6MΩ
AD5560
FORCE VOLTAGE LOOP
R
Z
C
:
C0
100pF
C
C1
6kΩ
100pF
C
C2
25kΩ
330pF
R
C
and ESR values, and
C3
100kΩ
200Ω TO 1MΩ
3.3nF
Figure 55. Block Diagram of a Force Amplifier Loop
R
P
:
FORCE
DAC
Rev. B | Page 34 of 60
+
8pF
g
m
–
AGND
V
SENSE
Table 12. External Variables
Name
C
R
C
R
I
Table 13. Internal Variables
Name
R
R
C
C
g
R
×1
R
C
D
D
Z
P
C0
F0
mx
:C
:C
+
–
F4
100kΩ
C3
200Ω
20kΩ
20Ω
2kΩ
Description
DUT capacitance with contributing
ESR
ESR in series with C
DUT capacitance with negligible ESR
Loading resistance at the DUT
Current range
Description
Resistor in series with C
contributes a zero.
Resistor to 8 pF to contribute an
additional pole
Capacitors to ensure unconditional
stability
Capacitors to optimize ac
performance into different C
Transconductance of force
amplifier input stage
+
–
+
–
EXTFORCE2
EXTFORCE1
DUTGND
FORCE
SENSE
C
C
C
C
C
F0
F1
F2
F3
F4
R
R
R
SENSE
SENSE
100nF
470nF
4.7nF
2.2µF
22nF
C0
, which
2
1
R
, C
D
C
D
C
R
Min
500 Ω
200 Ω
100 pF
4.7 nF
40 μA/V
Min
10 nF
1 mΩ
100 pF
~2 Ω
±5 μA
R
C
R
D
Max
160 μF
10 Ω
10 nF
Infinity
±1.2 A
Max
1.6 MΩ
1 MΩ
100 nF
10 μF
900 μA/
V