LTC1439 Linear Technology, LTC1439 Datasheet - Page 7

• Manufacturer Part Number: LTC1439
• Description: Dual High Efficiency/ Low Noise/ Synchronous Step-Down Switching Regulators
• Manufacturer: Linear Technology

TYPICAL PERFORMANCE CHARACTERISTICS
V
IC’s signal ground pin.
INTV
EXTV
ered from this voltage. Must be closely decoupled to
power ground with a minimum of 2.2 F tantalum or
electrolytic capacitor. The INTV
both RUN/SS1 and RUN/SS2 are low. Refer to the LTC1538/
LTC1539 for 5V keep-alive applications.
EXTV
switch closes and supplies INTV
low dropout regulator whenever EXTV
4.7V. Connect this pin to V
higher output voltage. Do not exceed 10V on this pin. See
EXTV
BOOST 1, BOOST 2: Supplies to the Topside Floating
Drivers. The bootstrap capacitors are returned to these
pins. Voltage swing at these pins is from INTV
V
SW1, SW2: Switch Node Connections to Inductors. Volt-
age swing at these pins is from a Schottky diode (external)
voltage drop below ground to V
PIN
IN
IN
U
: Main Supply Pin. Must be closely decoupled to the
+ INTV
CC
CC
CC
CC
FUNCTIONS
: Output of the Internal 5V Regulator and the
: External Power Input to an Internal Switch. This
connection in Applications Information section.
Switch. The driver and control circuits are pow-
CC
U
.
20
15
10
5
0
0
Auxiliary Regulator
Sink Current Available
U
2
4
AUX DR VOLTAGE (V)
OUT
W
6
CC
of the controller with the
CC,
IN
U
regulator turns off when
.
8
bypassing the internal
10
CC
12
is higher than
14
1438 G19
16
CC
to
SGND: Small-Signal Ground. Common to both control-
lers, must be routed separately from high current grounds
to the (–) terminals of the C
PGND: Driver Power Ground. Connects to sources of
bottom N-channel MOSFETs and the (–) terminals of C
SENSE
current comparators. Except for the LTC1438-ADJ, SENSE
1 is internally connected to the first controller’s V
sensing point. The first controller can only be used as a
3.3V or 5.0V regulator controlled by the V
the LTC1438, LTC1438X and LTC1439. The LTC1438-ADJ
Controller 1 implements a remote sensing adjustable
regulator. The second controller can be set to a 3.3V, 5.0V
or an adjustable regulator controlled by the V
(see Table 1).
Table 1. Output Voltage Table
Controller 1
Controller 2
70
60
50
40
30
20
10
–
10
Auxiliary Regulator PSRR
1, SENSE
Remote Sensing
Adjustable Only
Adjustable Only
LTC1438-ADJ
POR2 Output
FREQUENCY (kHz)
–
2: Connects to the (–) input for the
100
Secondary Feedback Loop
10mA LOAD
100mA LOAD
LTC1438/LTC1439
LTC1438/LTC1438X
Remote Sensing
Adjustable Only
OUT
POR2 Output
capacitors.
1438 G20
5V or 3.3V Only
1000
PROG1
5V/3.3V/Adjustable
Remote Sensing
POR2 Output
LTC1439
PROG2
pin with
7
OUT
pin
IN
–
.