LTC3716EG Linear Technology, LTC3716EG Datasheet - Page 17

• Manufacturer Part Number: LTC3716EG
• Description: IC SW REG STP-DN 5BIT SYNC36SSOP
• Manufacturer: Linear Technology
• Type: Step-Down (Buck)r

Specifications of LTC3716EG

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 1.75 V
• Current - Output: 35mA
• Frequency - Switching: 120kHz ~ 310kHz
• Voltage - Input: 4 ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 36-SSOP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Power - Output: -

APPLICATIO S I FOR ATIO
Topside MOSFET Driver Supply (C
Functional Diagram)
External bootstrap capacitors C
the BOOST1 and BOOST2 pins supply the gate drive
voltages for the topside MOSFETs. Capacitor C
Functional Diagram is charged though diode D
INTV
turns on, the driver places the C
source of the desired MOSFET. This enhances the MOSFET
and turns on the topside switch. The switch node voltage,
SW, rises to V
The value of the boost capacitor C
times that of the total input capacitance of the topside
MOSFET(s). The reverse breakdown of D
than V
The final arbiter when defining the best gate drive ampli-
tude level will be the input supply current. If a change is
made that decreases input current, the efficiency has
improved. If the input current does not change then the
efficiency has not changed either.
Output Voltage
The LTC3716 has a true remote voltage sense capablity.
The sensing connections should be returned from the load
back to the differential amplifier’s inputs through a com-
mon, tightly coupled pair of PC traces. The differential
amplifier corrects for DC drops in both the power and
ground paths. The differential amplifier output signal is
R6
R5
Figure 5a. Secondary Output Loop with EXTV
CC
OPTIONAL EXTV
CONNECTION
5V < V
EXTV
FCB
IN(MAX).
when the SW pin is low. When the topside MOSFET
CC
SEC
LTC3716
< 7V
IN
and the BOOST pin rises to V
CC
PGND
SW1
TG1
BG1
U
V
IN
C
IN
N-CH
N-CH
U
+
B
B1
voltage across the gate-
1N4148
B
V
IN
and C
needs to be 30 to 100
W
B
T1
,D
B
3
B
) (Refer to
B2
1
must be greater
R
CC
SENSE
connected to
Connection
IN
+ V
V
U
2
SEC
4
B
+
+
B
INTVCC
in the
3716 F05a
from
1 F
C
V
OUT
OUT
.
divided down and compared with the internal precision
0.6V voltage reference by the error amplifier.
Output Voltage Programming
The output voltage is digitally programmed as defined in
Table 1 using the VID0 to VID4 logic input pins. The VID
logic inputs program a precision, 0.25% internal feedback
resistive divider. The LTC3716 has an output voltage
range of 0.6V to 1.75V in 25mV and 50mV steps.
Between the ATTENOUT pin and ground is a variable
resistor, R1, whose value is controlled by the five VID input
pins (VID0 to VID4). Another resistor, R2, between the
ATTENIN and the ATTENOUT pins completes the resistive
divider. The output voltage is thus set by the ratio of
(R1 + R2) to R1.
Each VID digital input is pulled up by a 40k resistor in
series with a diode from V
grounded to get a digital low input, and can be either
floated or connected to V
series diode is used to prevent the digital inputs from
being damaged or clamped if they are driven higher than
V
V
normally connected to INTV
other sources. If it is driven from another source, that
source must be in the range of 2.7V to 5.5V and must be
alive prior to enabling the LTC3716.
BIAS
BIAS
EXTV
. The digital inputs accept CMOS voltage levels.
is the supply voltage for the VID section. It is
CC
Figure 5b. Capacitive Charge Pump for EXTV
LTC3716
PGND
SW1
BG1
TG1
V
IN
C
IN
N-CH
N-CH
+
BIAS
to get a digital high input. The
BIAS
CC
BAT85
V
IN
but can be driven from
. Therefore, it must be
L1
VN2222LL
3
1
R
0.22 F
SENSE
LTC3716
2
4
CC
+
+
3716 F05b
17
BAT85
BAT85
C
V
OUT
OUT