Rainbow Electronics MAX744A - Manual (Page 7)

MAX730A/MAX738A/MAX744A
5V, Step-Down,
Current-Mode PWM DC-DC Converters
_______________________________________________________________________________________ 7
NAME FUNCTION
1 SHDN
Shutdown—active low. Ground to power-down chip, tie to V+ for normal operation.
Output voltage falls to 0V when
SHDN is low.
2 REF
3 SS
Soft-Start. Capacitor between SS and GND provides soft-start and short-circuit protection.
510k
Ω
resistor from SS to SHDN provides current boost.
2
3
4 CC
Compensation Capacitor Input externally compensates the outer feedback loop.
Connect to OUT with a 330pF capacitor.
5 OUT Output Voltage Sense Input provides regulation feedback sensing. Connect to +5V output.
6 GND Ground pins are internally connected. Connect both pins to ground.
7 LX Drain of internal P-channel power MOSFET.
7
8
9
8 V+
Supply-Voltage Input. Bypass to GND with 1µF ceramic and large-value electrolytic capaci-
tors in parallel. The 1µF capacitor must be as close to V+ and GND pins as possible.
N.C. No Connect—no internal connections to these pins.
10, 11
12, 13, 14
1, 15, 16
4, 5, 6
______________________________________________________________Pin Description
MAX730A
LOAD-TRANSIENT RESPONSE
50ms/div
A: VOUT, 50mV/div, DC-COUPLED
B: IOUT, 200mA/div, 20mA TO 300mA
V+ = 9V
MAX738A/MAX744A
LOAD-TRANSIENT RESPONSE
50ms/div
A: VOUT, 50mV/div, DC-COUPLED
B: IOUT, 500mA/div, 50mA TO 750mA
V+ = 12V
300mA
20mA
A
B
____________________________Typical Operating Characteristics (continued)
(Circuit of Figure 3, T
A
= +25°C, unless otherwise noted.)
16-PIN
WIDE SO
8-PIN
DIP/SO
Reference-Voltage Output (+1.23V) supplies up to 100µA for extended loads.
Bypass to GND with a capacitor that does not exceed 0.047µF.
750mA
50mA
A
B
PIN