LTM4600
PIN FUNCTIONS
(See Package Description for Pin Assignment)
V
IN
(Bank 1):
Power Input Pins. Apply input voltage be-
tween these pins and PGND pins. Recommend placing
input decoupling capacitance directly between V
IN
pins
and PGND pins.
f
ADJ
(Pin A15):
A 110k resistor from V
IN
to this pin sets
the one-shot timer current, thereby setting the switching
frequency. The LTM4600 switching frequency is typically
850kHz. An external resistor to ground can be selected to
reduce the one-shot timer current, thus lower the switching
frequency to accommodate a higher duty cycle step down
requirement. See the applications section.
SV
IN
(Pin A17):
Supply Pin for Internal PWM Controller. Leave
this pin open or add additional decoupling capacitance.
EXTV
CC
(Pin A19):
External 5V supply pin for controller. If
left open or grounded, the internal 5V linear regulator will
power the controller and MOSFET drivers. For high input
voltage applications, connecting this pin to an external
5V will reduce the power loss in the power module. The
EXTV
CC
voltage should never be higher than V
IN
.
V
OSET
(Pin A21):
The Negative Input of The Error Amplifier.
Internally, this pin is connected to V
OUT
with a 100k precision
resistor. Different output voltages can be programmed with
additional resistors between the V
OSET
and SGND pins.
COMP (Pin B23):
Current Control Threshold and Error
Amplifier Compensation Point. The current comparator
threshold increases with this control voltage. The voltage
ranges from 0V to 2.4V with 0.8V corresponding to zero
sense voltage (zero current).
SGND (Pin D23):
Signal Ground Pin. All small-signal
components should connect to this ground, which in turn
connects to PGND at one point.
RUN/SS (Pin F23):
Run and Soft-Start Control. Forcing
this pin below 0.8V will shut down the power supply.
Inside the power module, there is a 1000pF capacitor
which provides approximately 0.7ms soft-start time with
200μF output capacitance. Additional soft-start time can
be achieved by adding additional capacitance between the
RUN/SS and SGND pins. The internal short-circuit latchoff
can be disabled by adding a resistor between this pin and
the V
IN
pin. This pullup resistor must supply a minimum
5μA pull up current.
FCB (Pin G23):
Forced Continuous Input. Grounding this
pin enables forced continuous mode operation regardless
of load conditions. Tying this pin above 0.63V enables
discontinuous conduction mode to achieve high efficiency
operation at light loads. There is an internal 4.75K resistor
between the FCB and SGND pins.
PGOOD (Pin J23):
Output Voltage Power Good Indicator.
When the output voltage is within 10% of the nominal
voltage, the PGOOD is open drain output. Otherwise, this
pin is pulled to ground.
PGND (Bank 2):
Power ground pins for both input and
output returns.
V
OUT
(Bank 3):
Power Output Pins. Apply output load
between these pins and PGND pins. Recommend placing
High Frequency output decoupling capacitance directly
between these pins and PGND pins.
EXTV
CC
81
TOP VIEW
SV
IN
f
ADJ
V
OSET
91
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
6
401
39
301
29
201
19
101
09
001
98
88
99
78
89
68
79
58
69
48
59
49
38
V
OUT
BANK 3
94
06
17
28
84
95
07
18
85
96
08
74
75
86
97
64
65
76
87
54
55
66
77
44
45
56
67
34
35
46
57
24
25
36
47
14
04
15
26
37
93
PGND
BANK 2
23
4600 PN01
12
22
32
42
83
13
73
03
51
63
92
41
53
82
31
43
72
62
33
05
16
27
23
21
52
8
V
IN
BANK 1
02
11
01
9
71
61
7
6
5
4
3
2
1
A
B
C
D
E
F
G
H
J
K
COMP
SGND
RUN/SS
FCB
PGOOD
L
M
N
P
R
T
4600fc
LINER [ LINEAR TECHNOLOGY ]
