TC28C46EOE TELCOM [TelCom Semiconductor, Inc], TC28C46EOE Datasheet - Page 8

• Manufacturer Part Number: TC28C46EOE
• Description: CMOS CURRENT MODE PWM CONTROLLER
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

TC18C46
TC28C46
TC38C46
Selection of Timing Capacitor and Resistor
(C
1)
2)
3)
4-108
T
SYNC
We need to choose R
& R
First determine the frequency of operation F
the desired " dead" time", T
The current mirror in Fig. 6 , shows:
During discharge (T
2 m A out of C
charge it:
2 m A - I
DISCHARGE
10
CURRENT
I
I
CHG
CHG
T
)
= 3.5 V
= C
CHG
R
T
0.5V 3.5V
T
= C
2mA
T,
V
T
T
minus the I
.
D
), the discharge current pulls
T
Also,
Where,
and
V
T
and C
I CHARGE
8
,where
C T
D
CHG
T.
(see Fig.6 graph).
that keeps trying to
V = 3.5 - 0.5
T = T
3.5V
V= 3.0 Volts
T= T
= 3.0 Volts
R O
R T
CHG
D
9
R T
Figure 6. Oscillator Circuit
O
V DD
and
+
–
3.5V
Knowing T
PIN 8
PIN 10
OUTPUT DEAD TIME (T D )
D
T CHG
choosing R
Substituting and rearranging,
1/F O
C
T
T D
= T
TELCOM SEMICONDUCTOR, INC.
CMOS CURRENT MODE
3
D
T
PWM CONTROLLERS
permits calculation of C
(.002 - 3.5)
R
T
T .