PI354X-00 Datasheet, PDF (29/39 Pages) –

PI354x-00
80
0
Gain - dBV
Phase-Degrees
20
60
40
60
40
80
20
100
1
10
100
1000
10000
100000
1000000
Frequency- Hz
Figure 57 — PI354x-00 Input-Control Gain/Phase
100
Gain - dBV
Phase-Degrees
150
50
100
0
50
50
1
0
10
100
1000
10000
100000
1000000
Frequency- Hz
Figure 58 — PI354x-00 Output-Input Gain/Phase
( ⁽ ) ( ⁾ ) ^{GIN_CTL(s) = GMEAO •}
R_OUT + s R_ZI • C_COMP • R_OUT
1 + s • C_COMP + C_HF + s² • C_HF • C_COMP • R_ZI
• ^R2
R1 + R2
(6)
The transfer function of the error amplifier and compensator
(also known as the Input To Control transfer function) reveals
the response of a Type II amplifier with a low frequency pole
determined by Equation (7), a zero which sets the mid-band
gain determined by Equation (8) and a high frequency pole
determined by Equation (9). Figure 58 shows the calculated
Input To Control transfer function. Multiplying Equation (3) by
Equation (6) ; described by Equation (10), results in the total loop
gain (also known as the Output To Input transfer function). A
graph is shown in Figure 58. The strategy is to set the zero such
that the mid-band gain allows a high crossover frequency while
providing maximum phase boost at crossover, with proper gain
and phase margin.
1
( ) ( ) ^{FPLF =} 2 • π • R_ZI + R_OUT • C_COMP + C_HF ^{= 33Hz}
(7)
1
( ) ^{FZMB =} 2 • π • R_ZI // R_OUT • C_COMP ^{= 6.8kHz}
(8)
F_PHF =
C_HF + C_COMP
2 • π • (R_ZI // R_OUT) • C_COMP • C_HF
= 580kHz
(9)
G_{OUT_IN}(s) = G_CO(s) • G_{IN_CTL}(s)
(10)
Lighting Mode (LGH)
The Lighting (LGH) mode allows the PI354x-00 product family to
be able to operate in constant current mode (CC) so that it can
support a wide range of applications that require the ability to
regulate current or voltage. Primary applications are LED lighting,
battery / super-capacitor charging and high peak current pulse
transient load applications. The PI354x-00 product family can
operate in dual modes, either as a constant voltage (CV) regulator
or a constant current (CC) regulator. Both modes can be utilized
in a single system. The PI354x-00 family has a separate current
amplifier, called LGH, and built in 100mV lighting reference that
has its output connected to the EAO pin internally. If the current
through an external shunt starts to develop 100mV at the LGH
pin, the LGH amplifier will take over regulation by pulling down
on the EAO output until the current is in regulation according
to the designed shunt value. The LGH amplifier is a sink only
trans‑conductance amplifier (TCA). It does not source current.
In the event of an open LED string or open current signal, the
voltage loop can be set to regulate the output voltage to a safe or
desired value in CV mode.
Cool-Power^® ZVS Switching Regulators
Page 29 of 39
Rev 1.6
03/2017
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