L7986 STMicroelectronics, L7986 Datasheet - Page 37

• Manufacturer Part Number: L7986
• Description: 3A step-down switching regulator
• Manufacturer: STMicroelectronics

Specifications of L7986

• Low Dropout Operation: 100% duty cycle

L7986
7.2
Equation 40
where V
external power MOSFET.
Inverting buck-boost
The L7986 can implement the step-up/down converter with a negative output voltage.
Figure 34.
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
where the duty cycle is given by
Figure 36. 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 022450 Rev 1
=
------------------------------------------------------------------------------------------- -
V
Equation
IN
–
V
V
OUT
D
SW
=
V
42.
–
=
----------------------------- -
V
OUT
V
OUT
–
SWE
V
V
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
37/44
38,