GM432 Ver la hoja de datos (PDF) - Gamma Microelectronics Inc.
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Fabricante
GM432 Datasheet PDF : 13 Pages
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AA
MICROELECTRONICS
Power Management
GM432
1.24V ADJUSTABLE PRECISION SHUNT REGULATORS
Stability Boundary Conditions
A Note About Stability
16
TA=25°C
14
VKA=Vref
12
10
Stable
8
6
4
2
0
0.001
VKA=2V
VKA=3V
0.01
0.1
1
CL - Load Capacitance - µF
Tantalum Capacitors
1.0
TA=25°C
0.8
0.6
Stable
0.4
VKA=Vref
0.2 For VKA= 2 & 3V
Device does not
Oscillate
0
0.001
0.01
0.1
1
CL - Load Capacitance - µF
Tantalum Capacitors
When using the GM432 as a shunt regulator, you can
optimize stability by setting CL either (1) no load ca-
pacitance across the GM432, decouple at the load; or
(2) large capacitance across the GM432, optional de-
coupling at the load. The GM432 can become unsta-
ble with capacitances of approximately 10nF to 1µF
when cathode currents are less than 3mA or so, with
instability increasing as cathode current is reduced.
So, while the GM432 is happily stable at, for example,
cathode current of 10mA with a 0.1µF capacitor
across it, it can oscillate transiently as the cathode cur-
rent rises through the region of instability. To avoid
this problem completely, simply eliminate the capaci-
tor or select a very low or very high (e.g. 10µF) capac-
10
itor CL. Since you will probably want local decoupling
at the load, the best idea is to use no capacitance
across the device. Just the resistance and capaci-
tance of the PCB traces and vias will prevent local
load decoupling from causing transient oscillation dur-
ing start-up. If you place the GM432 right next to the
load, with the load decoupling capacitor directly
across it, you must use a capacitor of nF or 10µF.
R
10
+
IK
R1
_
CL
GM432
R2
* Stability boundary condition test shows that tantalum capacitors
are recommended to minimize the conditions that may cause
the device to oscillate.
8
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