L7986TA STMicroelectronics, L7986TA Datasheet - Page 12

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

Specifications of L7986TA

• Low Dropout Operation: 100% duty cycle

Functional description
5.3
12/43
Error amplifier and compensation
The error amplifier (E/A) provides the error signal to be compared with the sawtooth to
perform the pulse width modulation. Its non-inverting input is internally connected to a 0.6 V
voltage reference, while its inverting input (FB) and output (COMP) are externally available
for feedback and frequency compensation. In this device the error amplifier is a voltage
mode operational amplifier so with high DC gain and low output impedance.
The uncompensated error amplifier characteristics are the following:
Table 5.
In continuous conduction mode (CCM), the transfer function of the power section has two
poles due to the LC filter and one zero due to the ESR of the output capacitor. Different
kinds of compensation networks can be used depending on the ESR value of the output
capacitor. In case the zero introduced by the output capacitor helps to compensate the
double pole of the LC filter a type II compensation network can be used. Otherwise, a type
III compensation network has to be used (see
compensation network selection).
Anyway the methodology to compensate the loop is to introduce zeros to obtain a safe
phase margin.
Maximum source/sink current
Uncompensated error amplifier characteristics
Output voltage swing
Low frequency gain
Slew rate
GBWP
Doc ID 022098 Rev 1
Chapter 6.4
for details about the
17mA/25mA
0 to 3.3V
4.5MHz
100dB
7V/μs
L7986TA