L5985TR STMicroelectronics, L5985TR Datasheet - Page 17

• Manufacturer Part Number: L5985TR
• Description: IC REG SW 2A STEP DOWN 8-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L5985TR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 18 V
• Current - Output: 2A
• Frequency - Switching: 250kHz ~ 1MHz
• Voltage - Input: 2.9 ~ 18 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-VFQFN, 8-VFQFPN
• Power - Output: 1.5W
• Output Voltage: 3 V
• Output Current: 2 A
• Input Voltage: 2.9 V to 18 V
• Switching Frequency: 220 KHz to 275 KHz
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 100 %
• For Use With: 497-6387 - BOARD EVAL FOR L5985
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6861-2; L5985TR

L5985
5.4
Table 8.
Compensation network
The compensation network has to assure stability and good dynamic performance. The loop
of the L5985 is based on the voltage mode control. The error amplifier is a voltage
operational amplifier with high bandwidth. So selecting the compensation network the E/A
will be considered as ideal, that is, its bandwidth is much larger than the system one.
The transfer functions of PWM modulator and the output LC filter are studied. (see
The transfer of the function PWM modulator, from the error amplifier output (COMP pin) to
the OUT pin, results:
Equation 10
where V
generates a sawtooth amplitude directly proportional to the input voltage, that is:
Equation 11
In this way the PWM modulator gain results constant and equals to:
Equation 12
The synchronization of the device with an external clock provided trough SYNCH pin can
modifies the PWM modulator gain (see
and how to keep it constant in spite of the external synchronization)
Manufacturer
PANASONIC
MURATA
SANYO
TDK
S
is the sawtooth amplitude. As seen in
Output capacitors
GRM32
GRM31
ECJ
EEFCD
TPA/B/C
C3225
Series
Doc ID 13006 Rev 5
G
22 to 100
10 to 47
10 to 22
10 to 68
100 to 470
22 to 100
PW0
Cap value (μF)
Chapter 4.1
G
V
S
PW0
=
=
V
-------- -
V
IN
K V
s
=
⋅
Chapter
=
V
-------- -
V
IN
IN
s
--- -
K
1
to understand how this gain changes
=
9
6.3 to 25
6.3 to 25
6.3
6.3
4 to 16
6.3
Rated voltage (V)
4.1, the voltage feed forward
Application information
< 5
< 5
< 5
15 to 55
40 to 80
< 5
ESR (mΩ)
Figure
17/37
9)