LX1562IDM Microsemi Analog Mixed Signal Group, LX1562IDM Datasheet - Page 14

• Manufacturer Part Number: LX1562IDM
• Description: IC CONTROLLER PFC 13.1V 8SOIC
• Manufacturer: Microsemi Analog Mixed Signal Group

Specifications of LX1562IDM

• Mode: Discontinuous Conduction (DCM)
• Frequency - Switching: 1.7MHz
• Current - Startup: 200µA
• Voltage - Supply: 11 V ~ 25 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LX1562/1563
14
V
VOLTAGE REFERENCE
VOLTAGE REFERENCE
The voltage reference is a low drift bandgap design which pro-
vides a stable +2.5V output with maximum of ±1.5% initial ac-
curacy. This voltage is internally tied to the non-inverting in-
put of the amplifier and is not available for external connec-
tion. The initial accuracy of the reference includes error am-
plifier input offset voltage. Figure 26 shows typical variation of
the reference voltage vs. temperature.
FIGURE 26 —
C1
2.52
2.51
2.50
2.49
2.48
2.47
2.46
2.45
R
T
& C
-50
FIGURE 25 — START-UP CAPACITOR VOLTAGE
T
TIME CONSTANT
REFERENCE VOLTAGE (Including Offset) vs. TEMPERATURE
V
HYST
V
START
-25
(T
A
) Ambient Temperature - (°C)
(continued)
0
DISCHARGE
25
P R O D U C T D A T A B O O K 1 9 9 6 / 1 9 9 7
C1
S
E C O N D
50
BOOTSTRAP
WINDING
P
DISCHARGE
TIME
-G
R O D U C T I O N
V
C
75
CC
L
E N E R AT I O N
= 1nF
= 12V
100
I C D E S C R I P T I O N
125
P
t
O W E R
D
f = Line Freq.
ERROR AMPLIFIER
The error amplifier is an internally compensated op-amp with
access to the inverting input and the output pin. The non-
inverting input is internally connected to the voltage reference
and is not available for external connection. The amplifier is
designed for an open loop gain of 80dB, along with a typical
bandwidth of 1.7MHz and 49 degrees of phase margin. The
boost output voltage of the power factor pre-regulator is di-
vided down and monitored by the inverting input. Input bias
current (0.5µA max) can cause an output voltage error that is
equal to the product of the input bias current and the value of
the upper divider resistor. The amplifier's output is available
for external loop compensation. Typically, the loop bandwidth
is set below 10Hz in order to reject the low frequency ripple
associated with 2X the line frequency. For example, if the
error amplifier is configured as an integrator with 1.2Hz band-
width, it will have 40dB ripple rejection at 120Hz frequency.
This means that if the output of the error amp is allowed to
have 100mV of ripple, the boost converter must be limited to
less than 10V of ripple on its output.
during removal of the output load, a separate comparator moni-
tors the E.A. output voltage and compares it to an internal 1.8V
reference. When load is removed, E.A. output swings lower
than 1.8V, trips the comparator and turns output driver off till
the inverting input voltage drops below 2.5V. At this point, the
E.A. output swings positive, turns the output driver back on
and repeats the cycle until the load is returned to normal con-
dition.
the E.A. output is clamped to two diode drops above the refer-
ence voltage. This prohibits the amplifier from being satu-
rated, allowing it to recover faster thus minimizing the boost
voltage overshoot.
A T A
F
To prevent boost output run away condition that may occur
To reduce output overshoot during line and load transients,
2f
FIGURE 27 — THE AMPLIFIER CONFIGURED AS AN INTEGRATOR
A C T O R
R10
R9
V
O
S
I
9
C
H E E T
1
O N T R O L L E R
Bias
V
REF
FOR LOOP COMPENSATION
C4
1.8V
From I
2
DET
Logic
BW =
I
9
>> I
BIAS
2 R
1
9
C4
Copyright © 1996
Rev. 1.3a
7
OUTPUT
DRIVE
8/30