鈥?/div>
DESCRIPTION
The UCC3941 family of low input voltage single inductor boost converters
are optimized to operate from a single or dual alkaline cell, and step up to
a 3.3V, 5V, or an adjustable output at 500mW. The UCC3941 family also
provides an auxiliary 9V 100mW output, primarily for the gate drive supply,
which can be used for applications requiring an auxiliary output such as a
5V supply by linear regulating. The primary output will start up under full
load at input voltages typically as low as 0.8V, with a guaranteed maximum
of 1V, and will operate down to 0.4V once the converter is operating, maxi-
mizing battery utilization.
Demanding applications such as Pagers and PDA鈥檚 require high efficiency
Adjustable Output Power Limit Control
from several milli-watts to several hundred milli-watts, and the UCC3941
family accommodates these applications with >80% typical efficiencies
Output Fully Disconnected in
over the wide range of operation. The high efficiency at low output current
Shutdown
is achieved by optimizing switching and conduction losses along with low
quiescent current. At higher output current the 0.25鈩?switch, and 0.4鈩?syn-
Adaptive Current Mode Control for
chronous rectifier, along with continuous mode conduction, provide high ef-
Optimum Efficiency
ficiency. The wide input voltage range on the UCC3941 family can
8碌A Shutdown Supply Current
accommodate other power sources such as NiCd and NiMH.
Other features include maximum power control and shutdown control.
Packages available are the 8-pin SOIC (D) and 8-pin DIP (N or J).
SIMPLIFIED BLOCK DIAGRAM AND APPLICATION CIRCUIT
+
22碌H
10碌F
0.8V TO VOUT +0.5V
VIN
SW
3
8V
VGD
8
0.4鈩?/div>
UCC3941-3 = 3.3V
UCC3941-5 = 5.0V
UCC3941-ADJ = 1.30V TO 6V
VOUT
2
10碌F
STARTUP
CIRCUITRY
0.25鈩?/div>
1
100碌F
PLIM
SD
5
4
OPEN=SD
*SGND/FB
鈥?/div>
+
UCC3941-ADJ
1.25V
6
PGND
*FOR UCC3941-ADJ ONLY:
PIN 7 = SGND & PGND, PIN 6 = OUTPUT SENSE FEEDBACK, FB.
7
UDG-98147
SLUS242 - JULY 1999
FOR UCC3941-ADJ ONLY
MODULATOR CONTROL CIRCUIT
SYNCHRONOUS RECTIFICATION CIRCUITRY
ANTI-CROSS CONDUCTION
STARTUP
MULTIPLEXING LOGIC
MAXIMUM INPUT POWER CONTROL
ADAPTIVE CURRENT CONTROL
1
2
3
4
5
6
7
8
9
10
11
