Device Architecture
2-40 Revision 4
1.5 V Voltage Regulator
The 1.5 V voltage regulator uses an external pass transistor to generate 1.5 V from a 3.3 V supply. The
base of the pass transistor is tied to PTBASE, the collector is tied to 3.3 V, and an emitter is tied to
PTBASE and the 1.5 V supplies of the Fusion device. Figure 2-27 on page 2-33 shows the hook-up of
the 1.5 V voltage regulator to an external pass transistor.
Microsemi recommends using a PN2222A or 2N2222A transistor. The gain of such a transistor is
approximately 25, with a maximum base current of 20 mA. The maximum current that can be supported
is 0.5 A. Transistors with different gain can also be used for different current requirements.
Table 2-18 • Electrical Characteristics
VCC33A = 3.3 V
Symbol Parameter Condition Min Typical Max Units
VOUT Output Voltage Tj = 25ºC 1.425 1.5 1.575 V
ICC33A Operation Current Tj = 25ºC ILOAD = 1 mA
ILOAD = 100 mA
ILOAD = 0.5 A
11
11
30
mA
mA
mA
VOUT
Load Regulation Tj = 25ºC ILOAD = 1 mA to 0.5 A 90 mV
VOUT Line Regulation Tj = 25ºC VCC33A = 2.97 V to 3.63 V
ILOAD = 1 mA
VCC33A = 2.97 V to 3.63 V
ILOAD = 100 mA
VCC33A = 2.97 V to 3.63 V
ILOAD = 500 mA
10.6
12.1
10.6
mV/V
mV/V
mV/V
Dropout Voltage* Tj = 25ºC ILOAD = 1 mA
ILOAD = 100 mA
ILOAD = 0.5 A
0.63
0.84
1.35
V
V
V
IPTBAS
E
PTBase Current Tj = 25ºC ILOAD = 1 mA
ILOAD = 100 mA
ILOAD = 0.5 A
48
736
12 20
µA
µA
mA
Note: *Data collected with 2N2222A.