AN8819NFB Datasheet, PDF (11/11 Pages) Panasonic Semiconductor – 4Ch. Linear Driver IC DC-DC Converter Control for CD

ICs for CD/CD-ROM Player
AN8819NFB
• DC-DC Converter Portion
3.4V regulator can be constructed by using external components. The output voltage can be made variable by using an external
resistance.
The short-circuit protective function stops switching of OUT pin (Pin3), unless the output of error amplifier (Pin4) reaches L
after H, within t = CSPRO × VTH/ISPRO (VTH = 1.1V ISPRO = 30µA). (It is recommended that an electrolytic capacitor of 4.7µF
around should be used for Pin3.)
The soft start function works by attaching a capacitor to Pin2 for GND. t = CDED × R (R = 60kΩ)
Also, MAX duty can be changed by attaching an external resistance to Pin2. The output voltage is determined as follows:
(Example)
SVCC
Assuming R1 + R2 = 50kΩ
11
1.11V
R1
R3
R1 × R3
R1 + R3
+
R2 × R4
R2 + R4
+
IC Inside
SVCC = 1.1 ×
–
R2 × R4
5
R2 + R4
R2
IN
R4
FB ⁴
Where
R3 = 26.9kΩ
R4 = 13.1kΩ
• Ripple Filter Portion for DA Converter (Ripple Filter of Low Saturation Voltage Type)
Attach a capacitor for noise removal to CRIP pin for GND.
(A capacitor of 22µF around is recommended.) Output current : 10mA (typ.)
• Battery Voltage Detection Circuit
The voltage applied to VSEN pin (Pin10) and the constant voltage are compared for output to EMP pin (Pin37).
There is approx. 50mV of hysteresis from detection to reset to prevent the output chattering.
The detection threshold voltage can be made variable by an external resistance.
The threshold values with no external resistances at VSEN pin (Pin10) are as follows:
Detection : VSEN = 2.2V (typ.) BSEL (Pin9) = L
Reset : VSEN = 2.25V (typ.) BSEL (Pin9) = L
Detection : VSEN = 1.8V (typ.) BSEL (Pin9) = HiZ
Reset : VSEN = 1.85V (typ.) BSEL (Pin9) = HiZ
Use the following equation as reference to determine the detection threshold voltage:
VSEN’
R1
VSEN
10
Assuming that the voltage of VSEN (Pin10) at battery
shortage detection is VSEN’
R2
VSEN’ =
R1 + R2 + R3
R3
× 1.25
R3
IC Inside
37
EMP
1.25V
Where
R1 : External Resistance
R2 : 8.0kΩ
R3 : 16.5kΩ (BSEL = HiZ)
R3 : 10.5kΩ (BSEL = L)
• RESET and MRST Portions
RESET (Pin35) is changed from L to H, and MRST pin is changed from H to L, with approx. 90% of the output voltage by a DC-
DC converter.