Page 1
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
1
DESCRIPTION
The SC1164/5 combines a synchronous voltage mode
controller with two low-dropout linear regulators
providing most of the circuitry necessary to implement
three DC/DC converters for powering advanced
microprocessors such as Pentium
®
II.
The SC1164/5 switching section features an integrated
5 bit D/A converter, pulse by pulse current limiting,
integrated power good signaling, and logic compatible
shutdown. The SC1164/5 switching section operates at
a fixed frequency of 200kHz, providing an optimum
compromise between size, efficiency and cost in the
intended application areas. The integrated D/A converter provides programmability of output voltage from
2.0V to 3.5V in 100mV increments and 1.30V to 2.05V
in 50mV increments with no external components.
The SC1164/5 linear sections are low dropout regulators. The SC1164 supplies 1.5V for GTL bus and 2.5V
for non-GTL I/O.
For the SC1165 both LDO’s are adjustable.
Pentium is a registered trademark of Intel Corporation
TEL:805-498-2111 FAX:805-498-3804 WEB:http://www.semtech.com
BLOCK DIAGRAMPIN CONFIGURATION
FEATURES
•
Synchronous design, enables no heatsink solution
•
95% efficiency (switching section)
•
5 bit DAC for output programmability
•
On chip power good function
•
Designed for Intel Pentium® ll requirements
•
1.5V, 2.5V or Adj. @ 1% for linear section
APPLICATIONS
•
Pentium® ll or Deschutes microprocessor supplies
•
Flexible motherboards
•
1.3V to 3.5V microprocessor supplies
•
Programmable triple power supplies
ORDERING INFORMATION
Part Number
(1)
Package
Linear
Voltage
Temp.
Range (T
J
)
SC1164CSW SO-24 1.5V/2.5V 0° to 125°C
SC1165CSW SO-24 Adj. 0° to 125°C
Note:
(1) Add suffix ‘TR’ for tape and reel.
Top View
(24 Pin SOIC)
AGND
GATE1
LDOS1
LDOS2
VCC
OVP
PWRGOOD
CS-
CS+
PGNDH
DH
PGNDL
1
2
3
LDOV
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VOSENSE
EN
BSTH
BSTL
DL
VID0
VID1
VID2
VID3
VID4
GATE2
2.5V/ADJ.
1.5V/ADJ.
1.265V
FET
CONTROLLER
REF.
FET
CONTROLLER
REF.
LDOV
Page 2
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
2
Parameter Symbol Maximum Units
VCC to GND VCC -0.3 to +7 V
PGND to GND ± 1 V
BST to GND -0.3 to +15 V
Operating Temperature Range T
A
0 to +70 °C
Junction Temperature Range T
J
0 to +125 °C
Storage Temperature Range T
STG
-65 to +150 °C
Lead Temperature (Soldering) 10 seconds T
L
300 °C
Thermal Impedance Junction to Ambient
θ
JA
80 °C/W
Thermal Impedance Junction to Case
θ
JC
25 °C/W
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
Unless specified: V CC = 4. 75V to 5.25V; GND = PGND = 0V; VOSE NS E = VO; 0mV < (CS+-CS-) < 60mV ; LDOV = 11.4V to 12.6V; TA = 25°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Switching Section
Output Voltage I
O
= 2A See Note 1.
Supply Voltage VCC 4.5 7 V
Supply Current VCC = 5.0V 8 15 mA
Load Regulation I
O
= 0.8A to 15A 1 %
Line Regulation 0.5 %
Current Limit Voltage 55 70 85 mV
Oscillator Frequency 175 200 225 kHz
Oscillator Max Duty Cycle 90 95 %
Peak DH Sink/Source Current BSTH-DH = 4.5V, DH-PGNDH = 3V 1 A
Peak DL Sink/Source Current BSTL-DL = 4.5V, DL-PGNDL = 3V 1 A
Output Voltage Tempco 65 ppm/
o
C
Gain (A
OL
) VOSENSE to V
O
35 dB
OVP threshold voltage 120 %
OVP source current V
OVP
= 3.0V 10 mA
Power good threshold voltage 85 115 %
Dead time 50 100 ns
Linear Sections
Quiescent current LDOV = 12V 5 mA
Output Voltage (LDO1 SC1164) 2.475 2.500 2.525 V
Output Voltage (LDO2 SC1164) 1.485 1.500 1.515 V
Reference Voltage (SC1165) 1.252 1.265 1.278 V
Feedback Pin Bias Current (SC1165) 10 uA
Gain (A
OL
) LDOS (1,2) to GATE (1,2) 90 dB
Load Regulation I
O
= 0 to 8A
(2)
0.3 %
Line Regulation 0.3 %
Output Impedance 1
K
Ω
Notes:
(1) See Output Voltage table.
(2) In application circuit.
Page 3
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
3
Note:
(1) All logic level inputs and outputs are open
collector TTL compatible.
PIN DESCRIPTION
Pin Pin Name Pin Function
1 AGND Small Signal Analog and Digital Ground
2 GATE1 Gate Drive Output LDO1
3 LDOS1 Sense Input for LDO1
4 LDOS2 Sense Input for LDO2
5 VCC Input Voltage
6 OVP High Signal out if V
O
>setpoint +20%
7 PWRGOOD
(1)
Open collector logic output, high if V
O
within 10% of setpoint
8 CS- Current Sense Input (negative)
9 CS+ Current Sense Input (positive)
10 PGNDH Power Ground for High Side Switch
11 DH High Side Driver Output
12 PGNDL Power Ground for Low Side Switch
13 DL Low Side Driver Output
14 BSTL Supply for Low Side Driver
15 BSTH Supply for High Side Driver
16 EN
(1)
Logic low shuts down the converter;
High or open for normal operation.
17 VOSENSE Top end of internal feedback chain
18
VID4
(1)
Programming Input (MSB)
19
VID3
(1)
Programming Input
20
VID2
(1)
Programming Input
21
VID1
(1)
Programming Input
22
VID0
(1)
Programming Input (LSB)
23 LDOV +12V for LDO section
24 GATE2 Gate Drive Output LDO2
Top View
(24 Pin SOIC)
AGND
GATE1
LDOS1
LDOS2
VCC
OVP
PWRGOOD
CS-
CS+
PGNDH
DH
PGNDL
1
2
3
LDOV
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
VOSENSE
EN
BSTH
BSTL
DL
VID0
VID1
VID2
VID3
VID4
GATE2
Page 4
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
4
OUTPUT VOLTAGE
Unless specified: VCC = 5.00V; GND = PGND = 0V; VOSENSE = VO; 0mV < (CS+-CS-) < 60mV; T
A
= 25oC
PARAMETER CONDITIONS VID
43210
MIN TYP MAX UNITS
Output Voltage I
O
= 2A in Application Circuit 01111 1.274 1.300 1.326
01110 1.323 1.350 1.377
01101 1.372 1.400 1.428
01100 1.421 1.450 1.479
01011 1.470 1.500 1.530
01010 1.527 1.550 1.573
01001 1.576 1.600 1.624
01000 1.625 1.650 1.675
00111 1.675 1.700 1.726
00110 1.724 1.750 1.776
00101 1.773 1.800 1.827
00100 1.822 1.850 1.878
00011 1.871 1.900 1.929
00010 1.921 1.950 1.979
00001 1.970 2.000 2.030
00000 2.019 2.050 2.081
11111 1.940 2.000 2.060
11110 2.058 2.100 2.142
11101 2.156 2.200 2.244
11100 2.254 2.300 2.346
11011 2.352 2.400 2.448
11010 2.450 2.500 2.550
11001 2.548 2.600 2.652
11000 2.646 2.700 2.754
10111 2.744 2.800 2.856
10110 2.842 2.900 2.958
10101 2.940 3.000 3.060
10100 3.038 3.100 3.162
10011 3.136 3.200 3.264
10010 3.234 3.300 3.366
10001 3.332 3.400 3.468
10000 3.430 3.500 3.570
Page 5
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
5
12V
5V
EN
VID3
VID2
VID1
VID0
OVP
VID4
PWRGD
VCC_CORE
VLIN2
VINLIN
VLIN1
C1
0.1uF
L1
4uH
R4
5mOhm
C18
0.1uF
+
C14
1500uF
+
C15
1500uF
+
C16
1500uF
+
C17
1500uF
+
C3
1500uF
+
C2
1500uF
R1
10
C13
0.1uF
Q2
BUK556
Q1
BUK556
C5
0.1uF
Q3
BUK556
+
C11
330uF
+
C12
330uF
R5
2.32k
U1
SC1164/5CSW
1
5
6
7
8
9
10
11
15
16
17
18
19
20
21
22
1312
1424
2 23
34
AGND
VCC
OVP
PWRGOOD
CS-
CS+
PGNDH
DH
BSTH
EN
VO SENSE
VID4
VID3
VID2
VID1
VID0
DLPGNDL
BSTLGATE2
GATE1 VDD
LDOS1LDOS2
Q4
BUK556
+
C9
330uF
+
C10
330uF
R6
1.00k
R12 *
R13 *
R15 *
R14 *
+
C21
330uF
+
C22
330uF
R16
TBD
R17
100k
R18
100k
NOTE: FOR SC1164, R12, R13, R14 AND R14 ARE NOT REQUIRED,
CONNECT LDOS1 (PIN3) DIRECTLY TO VLIN1 TO GENERATE 2.5V OUTPUT.
CONNECT LDOS2 (PIN4) DIRECTLY TO VLIN2 TO GENERATE 1.5V OUTPUT.
* SEE "SETTING LDO OUTPUT VOLTAGE" TABLE
** R17, R18 REQUIRED IF VINLIN CAN BE PRESENT WITHOUT 12V BEING
PRESENT.
**
**
(NORMALLY 3.3V)
APPLICATION CIRCUIT
Page 6
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
6
MATERIALS LIST
Qty. Reference Part/Description Vendor Notes
4 C1,C5,C13,C180.1µF Ceramic Various
6 C2,C3,C14-
C17
1500µF/6.3V SANYO MV-GX or equiv. Low ESR
6 C9-C12,
C21, C22
330µF/6.3V Various
1 L1 4µH 8 Turns 16AWG on MICROMETALS T50-52D core
4 Q1,Q2,Q3,Q4See notes See notes FET selection requires trade-off between efficiency and
cost. Absolute maximum R
DS(ON)
= 22 mΩ for Q1,Q2
1R4
5m
Ω
IRC OAR-1 Series
1R5
2.32kΩ, 1%, 1/8W
Various
1R6
1kΩ, 1%, 1/8W
Various
1R1
10Ω, 5%, 1/8W
Various
1 R12 1%, 1/8W Various See Table Below (Not required for SC1164)
1 R13 1%, 1/8W Various See Table Below (Not required for SC1164)
1 R14 1%, 1/8W Various See Table Below (Not required for SC1164)
1 R15 1%, 1/8W Various See Table Below (Not required for SC1164)
2 R17,R18
100kΩ, 5%,1/8W
Various Required if Voltage is applied to the linear FET(s) without
12V applied to SC1164/5
1 U1 SC1164/5CSW SEMTECH
SETTING LDO OUTPUT VOLTAGE
error tsignifican
cause not does term )RI( the that
so enoughlow be must R and R
ionclarificat for diagram layout See
resistor feedback Bottom R
resistor feedback Top R
current bias pin FeedbackI
:Where
)RI(
R
)RR(265.1
V
AFB
BA
B
A
FB
AFB
B
BA
OUT
⋅
=
=
=
⋅+
+⋅
=
R
B
R
A
VOUT LDO1 (LDO2) R12 (R14) R13 (R15)
3.45V
105
Ω
182
Ω
3.30V
105
Ω
169
Ω
3.10V
102
Ω
147
Ω
2.90V
100
Ω
130
Ω
2.80V
100
Ω
121
Ω
2.50V
100
Ω
97.6
Ω
1.50V
100
Ω
18.7
Ω
Page 7
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
7
70%
75%
80%
85%
90%
95%
0 2 4 6 8 10121416
Io (Amps)
Efficiency
3.5V Std
3.5V Sync
3.5V Sync Lo Rds
70%
75%
80%
85%
90%
95%
0 2 4 6 8 10 12 14 16
Io (Amps)
Efficiency
2.5V Std
2.5V Sync
2.5V Sync Lo Rds
70%
75%
80%
85%
90%
95%
0 2 4 6 8 10 12 14 16
Io (Amps)
Efficiency
2.8V Std
2.8V Sync
2.8V Sync Lo Rds
70%
75%
80%
85%
90%
95%
0 2 4 6 8 10 12 14 16
Io (Amps)
Efficiency
2.0V Std
2.0V Sync
2.0V Sync Lo Rds
Typical Ripple, Vo=2.8V, Io=10A
Typical Efficiency at Vo=2.5V
Typical Efficiency at Vo=3.5V Typical Efficiency at Vo=2.8V
Typical Efficiency at Vo=2.0V
Transient Response Vo=2.8V, Io=300mA to 10A
Page 8
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
8
LAYOUT GUIDELINES
Careful attention to layout requirements are necessary
for successful implementation of the SC1164/5 PWM
controller. High currents switching at 200kHz are present in the application and their effect on ground plane
voltage differentials must be understood and minimized.
1). The high power parts of the circuit should be laid out
first. A ground plane should be used, the number and
position of ground plane interruptions should be such
as to not unnecessarily compromise ground plane integrity. Isolated or semi-isolated areas of the ground
plane may be deliberately introduced to constrain
ground currents to particular areas, for example the input capacitor and bottom FET ground.
2). The loop formed by the Input Capacitor(s) (Cin), the
Top FET (Q1) and the Bottom FET (Q2) must be kept
as small as possible. This loop contains all the high current, fast transition switching. Connections should be as
wide and as short as possible to minimize loop inductance. Minimizing this loop area will a) reduce EMI, b)
lower ground injection currents, resulting in electrically
“cleaner” grounds for the rest of the system and c) minimize source ringing, resulting in more reliable gate
switching signals.
3). The connection between the junction of Q1, Q2 and
the output inductor should be a wide trace or copper
region. It should be as short as practical. Since this
connection has fast voltage transitions, keeping this
connection short will minimize EMI. The connection between the output inductor and the sense resistor should
be a wide trace or copper area, there are no fast voltage or current transitions in this connection and length
is not so important, however adding unnecessary
impedance will reduce efficiency.
Layout diagram for the SC1164/5
Vout
12V IN
5V Vo Lin1
Vo Lin2
5V
4uH
5mOhm
+
Cout
+
Cin
10
Q2
0.1uF
Q3
+
Cout Lin1
2.32k
Q4
+
Cout Lin2
1.00k
RB1
RA1
RA2
RB2
+
Cin Lin
SC1164/5
AGND
1
VCC
5
OVP
6
PWRGOOD
7
CS-
8
CS+
9
PGNDH
10
DH
11
BSTH
15
EN
16
VOSENSE
17
VID4
18
VID3
19
VID2
20
VID1
21
VID0
22
DL
13
PGNDL
12
BSTL
14
GATE2
24
GATE1
2
LDVO
23
LDOS1
3
LDOS2
4 Q1
0.1uF
Heavy lines indicate
high current paths.
are not required. LDOS1 connects to
For SC1164, RA1, RA2, RB1 and RB2
Vo Lin1, LDOS2 connects to Vo Lin2
Page 9
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
9
Vout
5V
+
+
4) The Output Capacitor(s) (Cout) should be located
as close to the load as possible, fast transient load
currents are supplied by Cout only, and connections
between Cout and the load must be short, wide copper areas to minimize inductance and resistance.
5) The SC1164/5 is best placed over a quiet ground
plane area, avoid pulse currents in the Cin, Q1, Q2
loop flowing in this area. PGNDH and PGNDL should
be returned to the ground plane close to the package.
The AGND pin should be connected to the ground
side of (one of) the output capacitor(s). If this is not
possible, the AGND pin may be connected to the
ground path between the Output Capacitor(s) and the
Cin, Q1, Q2 loop. Under no circumstances should
AGND be returned to a ground inside the Cin, Q1, Q2
loop.
6) Vcc for the SC1164/5 should be supplied from the
5V supply through a 10Ω resistor, the Vcc pin should
be decoupled directly to AGND by a 0.1µF ceramic
capacitor, trace lengths should be as short as possi-
ble.
7) The Current Sense resistor and the divider across
it should form as small a loop as possible, the traces
running back to CS+ and CS- on the SC1164/5 should
run parallel and close to each other. The 0.1µF capacitor should be mounted as close to the CS+ and
CS- pins as possible.
8) Ideally, the grounds for the two LDO sections
should be returned to the ground side of (one of) the
output capacitor(s).
Currents in various parts of the power section
Page 10
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
10
COMPONENT SELECTION
SWITCHING SECTION
OUTPUT CAPACITORS - Selection begins with the
most critical component. Because of fast transient load
current requirements in modern microprocessor core
supplies, the output capacitors must supply all transient
load current requirements until the current in the output
inductor ramps up to the new level. Output capacitor
ESR is therefore one of the most important criteria. The
maximum ESR can be simply calculated from:
step current Transient I
excursion voltage transient MaximumV
Where
I
V
R
t
t
t
t
ESR
=
=
≤
Each Capacitor Total
Technology C
(µF)
ESR
(mΩ)
Qty.
Rqd.C(µF)
ESR
(mΩ)
Low ESR Tantalum 330 60 6 2000 10
OS-CON 330 25 3 990 8.3
Low ESR Aluminum 1500 44 5 7500 8.8
()
OIN
t
ESR
VV
I
CR
L
−≤
OSC
IN
L
fL4
V
I
RIPPLE
⋅⋅
=
IN
O
)on(DS
2
OCOND
V
V
cycleduty =
where
RIP
≈δ
δ⋅⋅=
2
INOSW
10VIP
−
⋅⋅=
4
f)tt(VI
P
OSCfrINO
SW
⋅+⋅⋅
=
OSCINRRRR
fVQP
⋅⋅=
For example, to meet a 100mV transient limit with a
10A load step, the output capacitor ESR must be less
than 10mΩ. To meet this kind of ESR level, there are
three available capacitor technologies.
The choice of which to use is simply a cost/performance issue, with Low ESR Aluminum being the
cheapest, but taking up the most space.
INDUCTOR - Having decided on a suitable type and
value of output capacitor, the maximum allowable
value of inductor can be calculated. Too large an inductor will produce a slow current ramp rate and will
cause the output capacitor to supply more of the transient load current for longer - leading to an output voltage sag below the ESR excursion calculated above.
The maximum inductor value may be calculated from:
The calculated maximum inductor value assumes 100%
duty cycle, so some allowance must be made. Choosing
an inductor value of 50 to 75% of the calculated maximum will guarantee that the inductor current will ramp
fast enough to reduce the voltage dropped across the
ESR at a faster rate than the capacitor sags, hence ensuring a good recovery from transient with no additional
excursions.
We must also be concerned with ripple current in the
output inductor and a general rule of thumb has been to
allow 10% of maximum output current as ripple current.
Note that most of the output voltage ripple is produced
by the inductor ripple current flowing in the output capacitor ESR. Ripple current can be calculated from:
Ripple current allowance will define the minimum permitted inductor value.
POWER FETS - The FETs are chosen based on several
criteria with probably the most important being power
dissipation and power handling capability.
TOP FET - The power dissipation in the top FET is a
combination of conduction losses, switching losses and
bottom FET body diode recovery losses.
a) Conduction losses are simply calculated as:
b) Switching losses can be estimated by assuming a
switching time, if we assume 100ns then:
or more generally,
c) Body diode recovery losses are more difficult to estimate, but to a first approximation, it is reasonable to assume that the stored charge on the bottom FET body
diode will be moved through the top FET as it starts to
turn on. The resulting power dissipation in the top FET
will be:
To a first order approximation, it is convenient to only
consider conduction losses to determine FET suitability.
For a 5V in; 2.8V out at 14.2A requirement, typical FET
losses would be:
Page 11
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
11
)1(RIP
)on(DS
2
OCOND
δ−⋅⋅=
FET type
R
DS(on)
(mΩ)
P
D
(W) Package
BUK556H 22 2.48 TO220
IRL2203 7.0 0.79 D
2
PAK
Si4410 13.5 1.53 SO-8
FET type
R
DS(on)
(mΩ)
P
D
(W) Package
BUK556H 22 1.95 TO220
IRL2203 7.0 0.62 D
2
PAK
Si4410 13.5 1.20 SO-8
BOTTOM FET - Bottom FET losses are almost entirely
due to conduction. The body diode is forced into conduction at the beginning and end of the bottom switch conduction period, so when the FET turns on and off, there
is very little voltage across it, resulting in low switching
losses. Conduction losses for the FET can be determined by:
For the example above:
Each of the package types has a characteristic thermal
impedance, for the TO-220 package, thermal impedance
is mostly determined by the heatsink used. For the surface mount packages on double sided FR4, 2 oz printed
circuit board material, thermal impedances of 40
o
C/W
for the D
2
PAK and 80oC/W for the SO-8 are readily
achievable. The corresponding temperature rise is detailed below:
Temperature rise (oC)
FET type Top FET Bottom FET
BUK556H 49.6
(1)
39.0
(1)
IRL2203 31.6 24.8
Si4410 122.4 96
(1) With 20
o
C/W Heatsink
It is apparent that single SO-8 Si4410 are not adequate for
this application, but by using parallel pairs in each position, power dissipation will be approximately halved and
temperature rise reduced by a factor of 4.
INPUT CAPACITORS - since the RMS ripple current in
the input capacitors may be as high as 50% of the output current, suitable capacitors must be chosen accordingly. Also, during fast load transients, there may
be restrictions on input di/dt. These restrictions require
useable energy storage within the converter circuitry,
either as extra output capacitance or, more usually,
additional input capacitors. Choosing low ESR input
capacitors will help maximize ripple rating for a given
size.
Page 12
PROGRAMMABLE SYNCHRONOUS DC/DC
CONVERTER, DUAL LOW DROPOUT
REGULATOR CONTROLLER
© 1999 SEMTECH CORP.
October 25, 1999
652 MITCHELL ROAD NEWBURY PARK CA 91320
SC1164/5
12
OUTLINE DRAWING - SO-24
JEDEC MS-013AD
B17104B
ECN 99-667
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