TC28C43EOE TELCOM [TelCom Semiconductor, Inc], TC28C43EOE Datasheet - Page 4

• Manufacturer Part Number: TC28C43EOE
• Description: BiCMOS CURRENT MODE PWM CONTROLLERS
• Manufacturer: TELCOM [TelCom Semiconductor, Inc]

TC18C43
TC28C43
TC38C43
Pin No.
REFERENCE SECTION
amplifier to drive the output. It is unstable with capacitances
between 0.01 F and 3.3 F. In a normal application a 4.7 F
is used. In some lower noise layouts the capacitor can be
eliminated entirely.
power supplied. This is different than its bipolar counter-
parts, in that the bipolar reference comes on only after the IC
has come out of its under voltage mode. Thus, on the 38C4x,
the reference pin can not be used as a reset function such
as on a soft start circuit.
OSCILLATOR SECTION
resistor from the reference to the R
capacitor from this pin to ground. The oscillator is designed
to have ramp amplitude from 0.15 to 2.5 volts. This is
approximate, as over shoot on the oscillator comparator
causes the ramp amplitude to increase with frequency due
to comparator delay. Minimum values for C
33pF and 1k
dent on leakage currents in the capacitor, not on the input
currents to the R
4-96
PIN DESCRIPTION (Cont.)
FREQUENCY OF OPERATION
trolled by a resistor to V
(C
the capacitor until its voltage reaches the threshold of the
upper comparator ( 2.5V). A 2.5mA current is then applied
to the capacitor to discharge it to near ground ( 0.15V). The
discharge current is then shut off and the cycle repeats. An
approximate equation for the frequency of operation is:
8-Pin
T
). V
The reference is a zener-based design with a buffer
The oscillator frequency is set by the combination of a
The frequency of oscillation for the TC38C43 is con-
5
6
7
8
REF
The reference is active as soon as the 38C4x has
supplies current through the resistor and charges
Pin No
14-Pin
13
10
11
12
14
respectively. Maximum values are depen-
6
8
9
T
/C
T
pin.
REF
Pin No
16-Pin
10
11
12
13
14
15
16
7
8
9
(R
T
) and a capacitor to ground
POWER GROUND
ANALOG GND
Symbol
OUTPUT
T
V
V
NC
NC
NC
V
NC
/C
REF
DD
IN
T
pin and by a
T
and R
T
are
Description
No Connection
No Connection
No Connection
Ground return of output driver.
For all the low level analog signal returns.
Output to drive switching transistor gate input.
Supply power input terminal for the output drivers.
Voltage bias supply of all PWM Controller circuit functions.
Reference: 5.0 volt output.
No Connection.
upper and lower comparators each have delays. As R
smaller and as the frequency of operation gets higher, the
above equation is no longer valid.
The value of R
f
O
R
T
PIN NUMBERS FOR 14-PIN DIP
1
C
R T
C T
T
BiCMOS CURRENT MODE
T
(R
affects the discharge current and the
TELCOM SEMICONDUCTOR, INC.
T
14
in Ohms and C
7
9
PWM CONTROLLERS
V REF
R T /C T
GND
(5V)
T
in Farads)
T
gets