NAD T748 Service Manual page 37

NAME
RLIM3
SS3
COMP3
FB3
SYNC
ROSC
FB1
COMP1
SS1
RLIM1
EN1
BST1
VIN1
LX1
LX2
VIN2
BST2
EN2
RLIM2
SS2
COMP2
FB2
LOW_P
GND
PGOOD
V7V
V3V
AGND
GND
TERMINAL FUNCTIONS (DCA)
NO. I/O
1 I
2 I
3 O
4 I
5 I
6 I
7 I
8 O
9 I
10 I
11 I
12 I
13 I
14, 15 O
16, 17 O
18 I
19 I
20 I
21 I
22 I
23 O
24 I
25 I
26
27 O
28 O
29 O
30
31
Current limit setting for Buck 3. Fit a resistor from this pin to ground to set
the peak current limit on the output inductor.
Soft start pin for Buck 3. Fit a small ceramic capacitor to this pin to set the
converter soft start time.
Compensation for Buck 3. Fit a series RC circuit to this pin to complete
the compensation circuit of this converter.
Feedback input for Buck 3. Connect a divider set to 0.8V from the output
of the converter to ground.
Synchronous clock input. If there is a sync clock in the system, connect to
the pin. When not used connect to GND.
Oscillator set. This resistor sets the frequency of internal autonomous
clock. If external synchronization is used resistor should be fitted and set
to ~70% of external clock frequency.
Feedback pin for Buck 1. Connect a divider set to 0.8 V from the output of
the converter to ground.
Compensation pin for Buck 1. Fit a series RC circuit to this pin to
complete the compensation circuit of this converter.
Soft start pin for Buck 1. Fit a small ceramic capacitor to this pin to set the
converter soft start time.
Current limit setting pin for Buck 1. Fit a resistor from this pin to ground to
set the peak current limit on the output inductor.
Enable pin for Buck 1. A low level signal on this pin disables it. If pin is
left open a weak internal pull-up to V3V will allow for automatic enable.
For a delayed start-up add a small ceramic capacitor from this pin to
ground.
Bootstrap capacitor for Buck 1. Fit a 47-nF ceramic capacitor from this pin
to the switching node.
Input supply for Buck 1. Fit a 10-μF ceramic capacitor close to this pin.
Switching node for Buck 1
Switching node for Buck 2
Input supply for Buck 2. Fit a 10-μF ceramic capacitor close to this pin.
Bootstrap capacitor for Buck 2. Fit a 47-nF ceramic capacitor from this pin
to the switching node.
Enable pin for Buck 2. A low level signal on this pin disables it. If pin is
left open a weak internal pull-up to V3V will allow for automatic enable.
For a delayed start-up add a small ceramic capacitor from this pin to
ground.
Current limit setting for Buck 2. Fit a resistor from this pin to ground to set
the peak current limit on the output inductor.
Soft start pin for Buck 2. Fit a small ceramic capacitor to this pin to set the
converter soft start time.
Compensation pin for Buck 2. Fit a series RC circuit to this pin to
complete the compensation circuit of this converter
Feedback input for Buck 2. Connect a divider set to 0.8 V from the output
of the converter to ground.
Low power operation mode(active high) input for TPS65251
Ground pin
Power good. Open drain output asserted after all converters are
sequenced and within regulation. Polarity is factory selectable (active high
default).
Internal supply. Connect a 10-μF ceramic capacitor from this pin to
ground.
Internal supply. Connect a 10-μF ceramic capacitor from this pin to
ground.
Analog ground. Connect all GND pins and the power pad together.
Ground pin
2-25
DESCRIPTION