S3056
4. BTL Driver Circuits [Focus, Tracking, Sled, Spindle]
R4
R3
Va(+)
VI-Converter
Iconv
Vin
R1
Bias
Level Shift
-
+
Vo(+)
PAMP1
-
+
+
R2
Iconv(+)
Iconv(-)
R5
Va(-)
R6
+
-
Vo(-)
PAMP2
-
Pref
R7
BTL Driver Circuits are composed of VI-Converter, Level Shifter and Output power AMP.
VI-Converter converts voltage of Vin into current [Iconv ]
Iconv = (Vin – Bias ) / R1[10KΩ]
[ Closed loop Voltage Gain Calculation ]
Va(+) = (R2×Iconv ) + Pref
Va(-) = (-R5×Iconv) + Pref
Vo(+) = Va(+)×(1 + R4/R3 )
Vo(-) = Va(-)×( 1 + R7/R6 )
[ * R2 = R5 , R3 = R6, R4 = R7 * ]
Focus, Tracking closed loop Voltage Gain [ R2 = 25KΩ, R3 = 10KΩ, R4 = 20KΩ ]
Gain = 20 log [{ Vo(+) - Vo(-) } / (Vin - Bias) ]
= 20 log [{ Va(+)×( 1 + R3/R4 ) - Va(-)×( 1 + R6/R7 ) } / ( Vin – Bias ) ]
= 20 log [{(R2×Iconv ) + Pref }×( 1 + R4/R3 )]– [{(-R5×Iconv) + Pref }×( 1 + R7/R6 )]
(Vin – Bias )
= 20 log [2×(25K/10K)×{1+(20K/10K)} ]
= 23.5 [dB]
Sled closed loop Voltage Gain [R2 = 25KΩ, R3 = 10KΩ, R4 = 10KΩ ]
Gain = 20 log [2× (25K/10K)×{1+(10K/10K)} ]
= 20 [dB]
Spindle closed loop Voltage Gain [R2 = 15KΩ, R3 = 10KΩ, R4 = 10KΩ]
Gain = 20 log [2× (25K/10K)×{1+(10K/10K)} ]
= 15.5 [dB]
KSD-I7A004-001
SEPT., 2010 REV. 01
8
KODENSHI [ KODENSHI KOREA CORP. ]
