ISL6532 Intersil Corporation, ISL6532 Datasheet - Page 13

• Manufacturer Part Number: ISL6532
• Description: ACPI Regulator/Controller for Dual Channel DDR Memory Systems
• Manufacturer: Intersil Corporation

from the switching losses seen when sinking current. When
sourcing current, the upper MOSFET realizes most of the
switching losses. The lower switch realizes most of the
switching losses when the converter is sinking current (see
the equations below). These equations assume linear
voltage-current transitions and do not adequately model
power loss due the reverse-recovery of the upper and lower
MOSFET’s body diode. The gate-charge losses are
dissipated in part by the ISL6532 and do not significantly heat
the MOSFETs. However, large gate-charge increases the
switching interval, t
switching losses. Ensure that both MOSFETs are within their
maximum junction temperature at high ambient temperature
by calculating the temperature rise according to package
thermal-resistance specifications. A separate heatsink may be
necessary depending upon MOSFET power, package type,
ambient temperature and air flow.
1.25V
V
TT
V
REF
PGOOD
220µF
V
C
DDQ
20
0.1µF
V
C
+
DDQ
26
SW
0.1µF
C
+
27
which increases the MOSFET
220µF
C
21
10.0kΩ
FIGURE 7. DDR SDRAM AND AGP VOLTAGE REGULATOR USING THE ISL6532
R
0.47µF
2
13
C
19
+3.3V
S5
S3
C
1µF
17,18
PGOOD
SLP_S5#
SLP_S3#
VREF_OUT
VREF_IN
VTT
VTT
VTTSNS
5VSBY
ISL6532
ISL6532
VCC12
UGATE
LGATE
COMP
VDDQ
VDDQ
NCH
ISL6532 Application Circuit
Figure 7 shows an application circuit utilizing the ISL6532.
Detailed information on the circuit, including a complete Bill-
of-Materials and circuit board description, can be found in
Application Note AN1055.
Approximate Losses while Sinking current
FB
Approximate Losses while Sourcing current
C
1µF
16
P
P
P
P
LOWER
UPPER
UPPER
LOWER
Where: D is the duty cycle = V
4.99kΩ
= Io
= Io
R
=
=
t
f
1
SW
s
6.8nF
C
Io
2
Io
is the switching frequency.
2
14
2
x r
x r
2
is the combined switch ON and OFF time, and
1000pF
×
×
C
DS(ON)
DS(ON)
r
15
r
DS ON
19.1kΩ
DS ON
R
(
3
(
VCC5
x D
x (1 - D)
)
)
Q
×
Q
Q
×
L
2.1µH
5
1,3
56nF
D
2,4
825Ω
C
(
1
R
1 D
13
+
6
2.1µH
–
1.74kΩ
1
-- - Io
2
OUT
L
R
2
⋅
4
)
22.6Ω
C
1µF
+
R
4,5
/ V
5
×
1
-- - Io
2
V
⋅
IN
IN
,
+
×
×
V
+
t
2200µF
SW
IN
C
1-3
1800µF
×
C
×
6-8
t
f
SW
s
V
2.5V
DDQ
×
C
22µF
f
9-12
s