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Application Notes
Increasing the PT7761 Output Current with
the PT7769 Compatible Current Booster
The PT7769 is a 40-A “Current Booster” module
for the PT7761 regulator. The booster is controlled
directly by the regulator, and effectively adds a
parallel output stage. This allows the system to run
sychronously, providing a low noise solution. Up to
three booster modules can be connected to a single
regulator. Each booster increases the available output
current by 40A. Combinations of a regulator and
booster modules can supply power for virtually any
multi-processor application.
A current booster is not a stand-alone product, and
can only operate with a regulator. It is housed in
the same package as its compatible regulator, and
shares the same mechanical outline. Except for an
increase in output current, the overall performance
of a PT7761/booster combination is identical to
that of a stand-alone regulator. Refer to the appro-
priate data sheet for the performance specifications.
PT7761, PT7769
Current Booster Application Schematic
C
IN
+
C
OUT
+
LOAD
V
IN
VID0
VID1
VID2
VID3
V
OUT
GND
STBY*
L
IN
1 H
REMOTE SENSE ( – )
REMOTE SENSE ( + )
PROGRAMMING PINS
C
IN
+
L
IN
1 H
VID4
C
OUT
+
PT7761
43
2
1
3 1
23 – 30
15
61 6 – 22
9 – 14
5
7
Sync
GND
Sns (+)
Sns (–)
V
OUT
V
IN
Stby
VID0 - VID4
PT7769
7
23 – 30
16 – 22
9 – 14
Synch
V
OUT
GND
V
OUT
To
Additional
Boosters
Table 1; PT7769 Pin-Out Information
Pin Function
1
No Connect
11 Vin
21 GND
2
No Connect
12 Vin
22 GND
3No Connect
13Vin
23Vout
4
No Connect
14 Vin
24 Vout
5
No Connect
15 No Connect
25 Vout
6
No Connect
16 GND
26 Vout
7
Sync
17 GND
27 Vout
8
No Connect
18 GND
28 Vout
9Vin
19 GND
29 Vout
10 Vin
20 GND
30 Vout
31 No Connect
Notes:
1. Each booster requires the same amount of input and
output capacitance as recommended for a stand-alone
regulator. See the Standard Application schematic and
the respective input/output filter notes in the PT7761
product data sheet. Recommendations on specific
capacitor types are also detailed in the application note,
“Capacitor Recommendations for the PT7761
Integrated Switching Regulator.”
2. The 1-H filter choke located at the input of each
regulator and booster module (Lin) is optional for most
applications. If specified, each inductor must be sized
to handle 30ADC at full output load.
3. The pin-out of the current booster modules include a
number pins identified, “No Connect” (see Table 1).
These pins are not connected internally to the module
but must be soldered to a pad to preserve the unit’s
mechanical integrity.
4. A similar PCB footprint and trace layout between the
regulator and each booster will facilitate current sharing
between all modules.