L7986TA STMicroelectronics, L7986TA Datasheet - Page 37

• Manufacturer Part Number: L7986TA
• Description: 3A step-down switching regulator
• Manufacturer: STMicroelectronics

Specifications of L7986TA

• Low Dropout Operation: 100% duty cycle

L7986TA
7.2
Equation 40
where V
external power MOSFET.
Inverting buck-boost
The L7986TA can implement the step-up/down converter with a negative output voltage.
Figure 33.
to the standard buck topology.
The relationship between input and output voltage is:
Equation 41
So the duty cycle is:
Equation 42
As in the positive one, in the inverting buck-boost the current flowing through the power
MOSFET is transferred to the load only during the OFF time. So according to the maximum
DC switch current (3.0 A), the maximum output current can be calculated from the
38, where the duty cycle is given by
Figure 35. Inverting buck-boost regulator
D
is the voltage drop across the diodes, V
shows the schematic to regulate -5 V: no further external components are added
D
Doc ID 022098 Rev 1
=
------------------------------------------------------------------------------------------- -
V
IN
–
Equation
V
V
OUT
D
SW
=
V
–
=
----------------------------- -
V
OUT
V
OUT
–
SWE
V
V
42.
OUT
IN
+
–
2 V
⋅
+
SW
V
------------ -
1 D
⋅
V
IN
D
–
OUT
D
and V
+
2 V
SWE
⋅
D
across the internal and
Application ideas
Equation
37/43