ZLR964222L
Line Module User Guide
15
Microsemi Corporation Confidential and Proprietary
voltages, usually via DC/DC converters. DC/DC converters can create switching noise on the input supply. Good
decoupling is recommended.
Figure 4 - ZLR964222L Buck-Boost ABS Switching Regulator
4.5.1 PNP Driver
The BBABS design, as well as buck-boost designes, use a level shifting driver that converts the SWOUT 3.3V level
to a level appropriate for a high side PNP switch. Fast switching is helped by capacitor CS1. This capacitor is
critical to efficient switching of the PNP and customers should not deviate from the value, voltage rating, or package
size recommended. CS1 is specified as 0.1 uF 25 V X7R 0603. Capacitors rated for 16 V or less or 0402 body
sizes should NOT be used. Failure to follow these recommendations could result in power supply failures.
Additionally, there is a DC path to maintain good base drive current. This circuit is comprised of Q3, RC1, and RE1.
Q3 sets the base drive current. This is set by the equation, Ibase = 3.3 V - (Q3Vbe / RE1). Assuming Vbe of Q3 is
0.65 V and RE1 is 100
then the base current drive of the ZXTP2103 PNP is 26.5 ma. The previous BBABS
design used 75
for RE1 which set a 35 ma base current, which is still acceptable. This was determined to be
higher than necessary for most designs, although some versions of the PNP power transistor may still need a
higher base drive to operate effectively. Resistor RC1 is used to provide some additional voltage drop to limit heat
dissipation in Q3.
4.5.2 Capacitor Requirements
The BBABS supply has been design and characterized using low cost electrolytic capacitors. Both CFL1 and CFH1
are required to be 10uF capacitors. Depending on ringing requirements CFH1 can either be 50V or 63V rated. The
design uses 63V for both capacitors to minimize the number of different components. CFL1 should have a RMS
ripple rating of at least 150mA (at 100kHz). General purpose capacitor ripple is usually rated at 120Hz operating
frequency. High frequency ripple ratings are usually 1.5 to 2 times the 120Hz rating, but be sure to observe supplier
data sheets. There are also 0.1uF ceramic capacitors used for high frequency filtering. CFL2 is a 0.1uF 50V, and
CFH2 is a 0.1uF 100V. These should be X5R or X7R ceramic capacitors.
SWOUTY
VBSENSE1
VBATL_VBAT
VBATH
SWISY
AGND
AGND
VSW
3.3V
3.3V
AGND
AGND
AGND
AGND
VSW = 12V (10V - 14V)
Note 1
PLACE NEAR miSLIC DEVICE
'13
Buck-Boost ABS Power Supply
DO NOT POPULATE FOR 1 FXS
MUST BE 100V FOR 1FXS
Minimum Isat >1.5A
With option to convert to 1FXS buck-boost fixed tracker
RE1 = 120R for 1FXS
DSW1:
BAV23C for 1FXS
DNP
Populate either DSW2 (BAV23S) or DSW3/DSW4 (2x BAV70)
CPF4
0.1uF
0805
100V
RCS1
3.48K
RLIM3
1R0
1/16W
0402
CP1
0.22uF
0805
100V
RPF1
5.1R
1206
RE1
100R
0603
5%
RC1
75R
0603
CFH2
0.1uF
0805
100V
RDS1
10R
1206
RDS2
5.1R
1206
RLIM4
1R0
1/16W
0402
CS1
100nF
25V
0603
+
CFL1
10uF
63V
RVBL1
51K
0603
5%
CCS1
220pF
RB1
1K
0402
DSW3
BAV70
1
3
2
DSW2
BAV23S
1
3
2
CFL2
0.1uF
0805
50V
+
CFH1
10uF
63V
RTH1
1K
0402
RLIM2
1R0
1/16W
0402
RPF3
10R
1206
L1
47uH
1.5A
8mm
RLIM1
1R0
1/16W
0402
CPF3
0.1uF
0805
50V
Q2
ZXTP2013Z
SOT89
-100V
Q3
MMBT3904
SOT-23
Q1
ZXTP2013G
SOT223
-100V
DSW4
BAV70
1
3
2
+
CSW1
220uF
25V
DSW1
BAV70
1
3
2
RP1
10K
0402
