Description
GM38C4x is fixed frequency, high performance, and cur-
rent- mode PWM controllers. Gamma's BiCMOS devices
are pin compatible with standard 384x bipolar devices but
with several improvements.
Undervoltage lockout circuitry allows the '42 and '44 ver-
sions to start up at 14.5V and operate down to 9V, and the
'43 and '45 versions start at 8.4V with operation down to
7.6V. All versions operate up to 16V.
When compared to bipolar 384x devices operating from a
15V supply, start-up current has been reduced to 50µA typi-
cal and operating current has been reduced to 4.0 mA typi-
cal. Decreased output rise/fall times drive larger MOSFETs,
and rail-to-rail output capability increases efficiency, espe-
cially at lower supply voltages. GM38C4x also features a
trimmed oscillator discharge current and bandgap refer-
ence.
GM38C4x denotes 8-pin plastic DIP and SOP packages.
Features
40ns output rise and 30ns output fall times
-40
°
to +85
°
C temp. range same as standard
UC284x
Low-power BiCMOS Process
Very low start-up current (50µA typical)
Low operating current (4mA typical)
CMOS outputs with rail-to-rail swing
500kHz current-mode operation
Pin-for-pin compatible with UC3842/ 3843
/ 3844/ 3845(A)
Trimmed oscillator discharge current
UVLO with hysteresis
Low cross-conduction currents
Application
Current-mode, off-line, switched-mode
power supplies
Current-mode, dc-to-dc converters.
Step-down "buck" regulators
Step-up "boost" regulators
Flyback, isolated regulators
Forward converters
Synchronous FET converters
GM38C42, GM38C43, GM38C44, GM38C45
1
www.gammamicro.com
GM 431
V0.1
GAMMA [ GAMMA MICROELECTRONICS INC. ]
