DATASHEET

Radiation Hardened and SEE Hardened 6A Synchronous
Buck Regulator
ISL70001ASEH
Features
The ISL70001ASEH is a radiation hardened and SEE hardened
high efficiency monolithic synchronous buck regulator with
integrated MOSFETs. This single chip power solution operates
over an input voltage range of 3V to 5.5V and provides a tightly
regulated output voltage that is externally adjustable from 0.8V
to ~85% of the input voltage. Output load current capacity is 6A
for TJ < +145°C.
• ±1% reference voltage over line, load, temperature and
radiation
The ISL70001ASEH utilizes peak current-mode control for
excellent output load transient response and features integrated
compensation and switches at a fixed frequency of 1MHz to
reduce component size and count. In application where two POLs
are needed, two ISL70001ASEH devices can be synchronized
180° out-of-phase to reduce the overall input RMS ripple current.
The internal synchronous power switches are optimized for high
efficiency and good thermal performance.
• Highly efficient: 94% peak efficiency
The ISL70001ASEH incorporates fault protection for the
regulator. The protection circuits include input undervoltage,
output undervoltage, and output overcurrent.
• Power-good output voltage monitor
High integration and class leading radiation tolerance makes
the ISL70001ASEH an ideal choice to power many of today’s
small form factor applications. Two devices can be
synchronized to provide a complete power solution for large
scale digital ICs, like field programmable gate arrays (FPGAs),
that require separate core and I/O voltages.
Applications
• FPGA, CPLD, DSP, CPU Core or I/O voltages
• Low-voltage, high-density distributed power systems
• Current mode control for excellent dynamic response
• Full mil-temp range operation (TA = -55°C to +125°C)
• 50% lower shutdown supply current than the ISL70001SEH
• Available in a thermally enhanced heatsink package - R48.B
• Operates from 3V to 5.5V supply
• Adjustable output voltage
- Two external resistors set VOUT from 0.8V to ~85% of VIN
• Bidirectional SYNC pin allows two devices to be synchronized
180° out-of-phase
• Adjustable analog soft-start
• Input undervoltage, output undervoltage and output
overcurrent protection
• Electrically screened to DLA SMD 5962-09225
• QML qualified per MIL-PRF-38535 requirements
• Radiation hardness
- Total dose [50-300rad(Si)/s] . . . . . . . . . . . . . . 100krad(Si)
- Total dose [<10mrad(Si)/s]. . . . . . . . . . . . . . . 100krad(Si)*
* Product capability established by initial characterization. The
EH version is acceptance tested on a wafer-by-wafer basis to
50krad(Si) at low dose rate.
• SEE hardness
- SEL and SEB LETeff . . . . . . . . . . . . 86.4MeV/mg/cm2 min
- SEFI X-section (LETeff = 86.4MeV/mg/cm2) 1.4 x 10-6 cm2
max
- SET LETeff (< 1 pulse perturbation) 86.4MeV/mg/cm2 min
Related Literature
• AN1842, “ISL70001ASEHEV1Z Evaluation Board”
100
ISL70001ASEH
CORE
SYNCH
ISL75051SEH
AUX
RAD TOLERANT
FPGA
EFFICIENCY (%)
95
5V Supply
90
85
1.5V
1.8V
3.3V
2.5V
80
1.2V
ISL70001ASEH
I/O
SYNCH
75
70
0
1
2
3
4
5
6
LOAD CURRENT (A)
FIGURE 1. TYPICAL APPLICATION
May 20, 2014
FN8365.2
1
FIGURE 2. EFFICIENCY 5V INPUT, TA = +25°C
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 | Copyright Intersil Americas LLC 2013, 2014. All Rights Reserved
Intersil (and design) is a trademark owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners.
ISL70001ASEH
EN
Functional Block Diagram
AVDD
POWER-ON
RESET (POR)
PORSEL
DVDD
PVINx
CURRENT
SENSE
SLOPE
COMPENSATION
SOFT
START
SS
EA
FB
GM
PWM
CONTROL
LOGIC
GATE
DRIVE
LXx
COMPENSATION
PGNDx
UV
POWER-GOOD
PGOOD
REF
PWM
REFERENCE
0.6V
TDI
BIT
TDO
TRIM
ZAP
SYNC
M/S
PGNDx
PGNDx
DGND
AGND
Ordering Information
ORDERING NUMBER
(Note 1)
PART NUMBER
TEMP. RANGE
(°C)
PACKAGE
(RoHS Compliant)
PKG.
DWG. #
5962R0922503VXC
ISL70001ASEHVF (Note 2)
-55 to +125
48 Ld CQFP
R48.A
5962R0922503VYC
ISL70001ASEHVFE (Note 2)
-55 to +125
48 Ld CQFP with Heatsink
R48.B
5962R0922503V9A
ISL70001ASEHVX
-55 to +125
Die
ISL70001ASEHF/PROTO
ISL70001ASEHF/PROTO (Note 2)
-55 to +125
48 Ld CQFP
R48.A
ISL70001ASEHFE/PROTO
ISL70001ASEHFE/PROTO (Note 2)
-55 to +125
48 Ld CQFP with Heatsink
R48.B
ISL70001ASEHX/SAMPLE
ISL70001ASEHX/SAMPLE
-55 to +125
Die
ISL70001ASEHEV1Z
ISL70001ASEHEV1Z
Evaluation Board
NOTES:
1. Specifications for Rad Hard QML devices are controlled by the Defense Logistics Agency Land and Maritime (DLA). The SMD
numbers listed in the Ordering Information table must be used when ordering.
2. These Intersil Pb-free Hermetic packaged products employ 100% Au plate - e4 termination finish, which is RoHS compliant
and compatible with both SnPb and Pb-free soldering operations.
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FN8365.2
May 20, 2014
ISL70001ASEH
Pin Configuration
PVIN3
PVIN2
2
PVIN2
PGND1
3
LX2
LX1
4
PGND2
PVIN1
5
PGND2
PVIN1
6
PGND1
SYNC
ISL70001ASEH
(48 LD CQFP)
TOP VIEW
M/S
7
1 48 47 46 45 44 43
42
ZAP
8
41
LX3
TDI
9
40
PGND3
TDO
10
39
PGND3
PGOOD
11
38
PGND4
37
PGND4
36
LX4
PVIN3
13
DVDD
14
35
PVIN4
DGND
15
34
PVIN4
DGND
16
33
PVIN5
AGND
17
32
PVIN5
AGND
31
18
19 20 21 22 23 24 25 26 27 28 29 30
PGND5
PGND6
PGND6
LX6
PVIN6
PVIN6
PORSEL
EN
FB
REF
* HEATSINK
PGND5
DVDD
AVDD
SS
12
LX5
* Heatsink available in R48.B package
Pin Descriptions
PIN NUMBER
PIN NAME
DESCRIPTION
1, 2, 27, 28, 29, 30,
37, 38, 39, 40, 47,
48
PGNDx
These pins are the power grounds associated with the corresponding internal power blocks. Connect these pins
directly to the ground plane. These pins should also connect to the negative terminals of the input and output
capacitors. Locate the input and output capacitors as close as possible to the IC.
3, 26, 31, 36, 41,
46
LXx
These pins are the outputs of the corresponding internal power blocks and should be connected to the output
filter inductor. Internally, these pins are connected to the synchronous MOSFET power switches. To minimize
voltage undershoot, it is recommended that a Schottky diode be connected from these pins to PGNDx. The
Schottky diode should be located as close as possible to the IC.
4, 5, 24, 25, 32, 33,
34, 35, 42, 43, 44,
45
PVINx
These pins are the power supply inputs to the corresponding internal power blocks. These pins must be
connected to a common power supply rail, which must fall in the range of 3V to 5.5V. Bypass these pins directly
to PGNDx with ceramic capacitors located as close as possible to the IC.
6
SYNC
This pin is the synchronization I/O for the IC. When configured as an output (Master Mode), this pin drives the
SYNC input of another ISL70001ASEH. When configured as an input (Slave Mode), this pin accepts the SYNC
output from another ISL70001ASEH or an external clock. Synchronization of the slave unit is 180° out-of-phase
with respect to the master unit. If synchronizing to an external clock, the clock must be SEE hardened and the
frequency must be within the range of 1MHz ±20%.
7
M/S
This pin is the Master/Slave input for selecting the direction of the bidirectional SYNC pin. For SYNC = Output
(Master Mode), connect this pin to DVDD. For SYNC = Input (Slave Mode), connect this pin to DGND.
8
ZAP
This pin is a trim input and is used to adjust various internal circuitry. Connect this pin to DGND.
9
TDI
This pin is the test data input of the internal BIT circuitry. Connect this pin to DGND.
10
TDO
This pin is the test data output of the internal BIT circuitry. Connect this pin to DGND.
11
PGOOD
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This pin is the power-good output. This pin is an open drain logic output that is pulled to DGND when the output
voltage is outside a ±11% typical regulation window. This pin can be pulled up to any voltage from 0V to 5.5V,
independent of the supply voltage. A nominal 1k to 10k pull-up resistor is recommended. Bypass this pin
to DGND with a 10nF ceramic capacitor to mitigate SEE.
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FN8365.2
May 20, 2014
ISL70001ASEH
Pin Descriptions (Continued)
PIN NUMBER
PIN NAME
DESCRIPTION
12
SS
This pin is the soft-start input. Connect a ceramic capacitor from this pin to DGND to set the soft-start output
ramp time in accordance with Equation 1:
t SS = C SS  V REF  I SS
(EQ. 1)
where:
tSS = Soft-start output ramp time
CSS = Soft-start capacitor
VREF = Reference voltage (0.6V typical)
ISS = Soft-start charging current (23µA typical)
Soft-start time is adjustable from approximately 2ms to 200ms.
The range of the soft-start capacitor should be 82nF to 8.2µF, inclusive.
13, 14
DVDD
These pins are the bias supply inputs to the internal digital control circuitry. Connect these pins together at the
IC and locally filter them to DGND using a 1 resistor and a 1µF ceramic capacitor. Locate both filter
components as close as possible to the IC.
15, 16
DGND
These pins are the digital ground associated with the internal digital control circuitry. Connect these pins
directly to the ground plane.
17, 18
AGND
These pins are the analog ground associated with the internal analog control circuitry. Connect these pins
directly to the ground plane.
19
AVDD
This pin is the bias supply input to the internal analog control circuitry. Locally filter this pin to AGND using a 1
resistor and a 1µF ceramic capacitor. Locate both filter components as close as possible to the IC.
20
REF
This pin is the internal reference voltage output. Bypass this pin to AGND with a 220nF ceramic capacitor
located as close as possible to the IC. The bypass capacitor is needed to mitigate SEE. No current (sourcing or
sinking) is available from this pin.
21
FB
This pin is the voltage feedback input to the internal error amplifier. Connect a resistor from FB to VOUT and
from FB to AGND to adjust the output voltage in accordance with Equation 2:
V OUT = V REF   1 +  R T  R B  
(EQ. 2)
where:
VOUT = Output voltage
VREF = Reference voltage (0.6V typical)
RT = Top divider resistor (Must be 1k)
RB = Bottom divider resistor
The top divider resistor must be 1k to mitigate SEE. Connect a 4.7nF ceramic capacitor across RT to mitigate SEE
and to improve stability margins.
22
EN
This pin is the enable input to the IC. This is a comparator type input with a rising threshold of 0.6V and
programmable hysteresis. Driving this pin above 0.6V enables the IC. Bypass this pin to AGND with a 10nF
ceramic capacitor to mitigate SEE.
23
PORSEL
This pin is the input for selecting the rising and falling POR (Power-On-Reset) thresholds. For a nominal 5V
supply, connect this pin to DVDD. For a nominal 3.3V supply, connect this pin to DGND. For nominal supply
voltages between 5V and 3.3V, connect this pin to DGND.
HEATSINK
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4
The heatsink is electrically isolated and should be connected to a thermal chassis of any potential which offers
optimal thermal relief.
FN8365.2
May 20, 2014
ISL70001ASEH
Typical Application Schematic
PVIN1
LX1
PVIN2
LX2
PVIN3
LX3
PVIN4
LX4
PVIN5
LX5
5V
100µF
1µF
1µF
1µH
LX6
PVIN6
1Ω
1kΩ
FB
1µF
ISL70001ASEH
0V TO 5.5V
AGND
499Ω
PGOOD
DVDD
VSENSE
470µF
20V
3A
AVDD
1Ω
1.8V
6A
10nF
1µF
SYNC
DGND
REF
EN
10nF
220nF
M/S
PORSEL
TDI
SS
TDO
100nF
PGND6
PGND5
PGND4
PGND3
PGND2
PGND1
ZAP
FIGURE 3. 5V INPUT SUPPLY VOLTAGE WITH MASTER MODE SYNCHRONIZATION
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FN8365.2
May 20, 2014
ISL70001ASEH
Typical Application Schematic (Continued)
PVIN1
LX1
PVIN2
LX2
PVIN3
LX3
PVIN4
LX4
PVIN5
LX5
3.3V
100µF
1µF
1µF
1µH
LX6
PVIN6
1Ω
470µF
20V
3A
DVDD
1kΩ
4.7nF
FB
1µF
ISL70001ASEH
0V TO 5.5V
DGND
1Ω
1.8V
6A
499Ω
PGOOD
AVDD
10nF
1µF
VSENSE
SYNC
AGND
REF
EN
10nF
220nF
M/S
PORSEL
TDI
SS
TDO
100nF
PGND6
PGND5
PGND4
PGND3
PGND2
PGND1
ZAP
FIGURE 4. 3.3V INPUT SUPPLY VOLTAGE WITH SLAVE MODE SYNCHRONIZATION
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FN8365.2
May 20, 2014
ISL70001ASEH
Absolute Maximum Ratings
Thermal Information
AVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AGND - 0.3V to AGND + 6.5V
DVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DGND - 0.3V to DGND +6.5V
LXx, PVINx . . . . . . . . . . . . . . . . . . . . . . . . . . . PGNDx - 0.3V to PGNDx + 6.5V
AVDD - AGND, DVDD - DGND . . . . . . . . . . . . . . . . . . . . PVINx - PGNDx ± 0.3V
Signal Pins (Note 8) . . . . . . . . . . . . . . . . . . . . . AGND - 0.3V to AVDD + 0.3V
Digital Control Pins (Note 9) . . . . . . . . . . . . . . DGND - 0.3V to DVDD + 0.3V
PGOOD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DGND - 0.3V to DGND + 6.5V
SS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DGND - 0.3V to DGND + 2.5V
Thermal Resistance (Typical)
JA (°C/W) JC (°C/W)
48 Ld CQFP R48.A (Notes 3, 5) . . . . . . . . .
36.5
3
48 Ld CQFP R48.B (Notes 4, 6) . . . . . . . . .
19
1.3
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . .+145°C
Storage Temperature Range. . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see TB493
Absolute Maximum Ratings (Note 7)
Recommended Operating Conditions
AVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AGND - 0.3V to AGND + 5.7V
DVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DGND - 0.3V to DGND + 5.7V
LXx, PVINx . . . . . . . . . . . . . . . . . . . . . . . . . . . PGNDx - 0.3V to PGNDx + 5.7V
AVDD - AGND, DVDD - DGND . . . . . . . . . . . . . . . . . . . . PVINx - PGNDx ± 0.3V
Signal Pins (Note 8) . . . . . . . . . . . . . . . . . . . . . AGND - 0.3V to AVDD + 0.3V
Digital Control Pins (Note 9) . . . . . . . . . . . . . . DGND - 0.3V to DVDD + 0.3V
PGOOD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DGND - 0.3V to DGND + 5.7V
SS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .DGND - 0.3V to DGND + 2.5V
AVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AGND + 3V to 5.5V
DVDD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DGND + 3V to 5.5V
PVINx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PGNDx + 3V to 5.5V
AVDD - AGND, DVDD - DGND . . . . . . . . . . . . . . . . . . . . PVINx - PGNDx ± 0.1V
Signal Pins (Note 8) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . AGND to AVDD
Digital Control Pins (Note 9) . . . . . . . . . . . . . . . . . . . . . . . . . .DGND to DVDD
REF, SS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internally Set
GND, TDI, TDO, TPGM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . DGND
ILXx (TJ ≤ +145°C) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0A to 1.0A
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . . .-55°C to +125°C
ESD Rating
Human Body Model (Tested per MIL-PRF-883 3015.7). . . . . . . . . . . 2kV
Machine Model (Tested per JESD22-A115-A) . . . . . . . . . . . . . . . . . 200V
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product
reliability and result in failures not covered by warranty.
NOTES:
3. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
4. JA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech
Brief TB379
5. For JC, the “case temp” location is the center of the package underside.
6. For JC, the “case temp” location is the center of the exposed metal pad on the package underside.
7. For operation in a heavy ion environment at LET = 86.4 MeV•cm2/mg with +125°C (TC).
8. EN, FB, PORSEL and REF pins.
9. M/S, SYNC, TDI, TDO and ZAP pins
Electrical Specifications
V
Unless otherwise noted, VIN = AVDD = DVDD = PVINx = EN = M/S = 3V or 5.5V;
GND = AGND = DGND = PGNDx = TDI = TDO = ZAP = 0V; FB = 0.65V; PORSEL = VIN for 4.5V ≤ VIN ≤ 5.5V and GND for VIN < 4.5V,
SYNC = LXx = Open Circuit; PGOOD is pulled up to VIN with a 1k resistor; REF is bypassed to GND with a 220nF capacitor; SS is bypassed to GND with a
100nF capacitor; IOUT = 0A; TA = TJ = +25°C (Note 12). Boldface limits apply across the operating temperature range, -55°C to +125°C; over a total
iodizing dose of 100krad(Si) with exposure at a high dose rate of 50 - 300krad(Si)/s; and over a total iodizing dose of 50krad(Si) with exposure at a low
dose rate of <10mrad(Si)/s.
PARAMETER
MIN
(Note 13)
TYP
(Note 12)
MAX
(Note 13)
UNITS
VIN = 5.5V (Note 10)
40
65
mA
VIN = 3.6V (Note 10)
25
45
mA
VIN = 5.5V, EN = GND (Note 11)
2
6
mA
VIN = 3.6V, EN = GND (Note 11)
1.5
4.5
mA
0.594
0.6
0.606
V
TEST CONDITIONS
POWER SUPPLY
Operating Supply Current
Shutdown Supply Current
OUTPUT VOLTAGE
Reference Voltage Tolerance
Output Voltage Tolerance
VOUT = 0.8V to 2.5V for VIN = 4.5V to 5.5V,
VOUT = 0.8V to 2.5V for VIN = 3V to 3.6V,
IOUT = 0A to 6A (Notes 14, 15)
-2
0
2
%
Feedback (FB) Input Leakage Current
VIN = 5.5V, VFB = 0.6V
-1
0
1
µA
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FN8365.2
May 20, 2014
ISL70001ASEH
Electrical Specifications
Unless otherwise noted, VIN = AVDD = DVDD = PVINx = EN = M/S = 3V or 5.5V;
GND = AGND = DGND = PGNDx = TDI = TDO = ZAP = 0V; FB = 0.65V; PORSEL = VIN for 4.5V ≤ VIN ≤ 5.5V and GND for VIN < 4.5V,
SYNC = LXx = Open Circuit; PGOOD is pulled up to VIN with a 1k resistor; REF is bypassed to GND with a 220nF capacitor; SS is bypassed to GND with a
100nF capacitor; IOUT = 0A; TA = TJ = +25°C (Note 12). Boldface limits apply across the operating temperature range, -55°C to +125°C; over a total
iodizing dose of 100krad(Si) with exposure at a high dose rate of 50 - 300krad(Si)/s; and over a total iodizing dose of 50krad(Si) with exposure at a low
dose rate of <10mrad(Si)/s. (Continued)
MIN
(Note 13)
TYP
(Note 12)
MAX
(Note 13)
UNITS
Oscillator Accuracy
0.85
1
1.15
MHz
External Oscillator Range
0.8
1
1.2
MHz
PARAMETER
TEST CONDITIONS
PWM CONTROL LOGIC
Minimum LXx On Time
VIN = 5.5V, Test Mode
110
150
ns
Minimum LXx Off Time
VIN = 5.5V, Test Mode
40
100
ns
Minimum LXx On Time
VIN = 3V, Test Mode
150
210
ns
Minimum LXx Off Time
VIN = 3V, Test Mode
50
100
ns
Master/Slave (M/S) Input Voltage
Input High Threshold
VIN - 0.5
Input Low Threshold
1.3
0.5
V
1
µA
Master/Slave (M/S) Input Leakage Current
VIN = 5.5V, M/S = GND or VIN
-1
0
Synchronization (SYNC) Input Voltage
Input High Threshold, M/S = GND
2.3
1.7
Input Low Threshold, M/S = GND
-1
V
1.2
V
1.5
1
V
0
1
µA
Synchronization (SYNC) Input Leakage
Current
VIN = 5.5V, M/S = GND, SYNC = GND or VIN
Synchronization (SYNC) Output Voltage
VIN - VOH at IOH = -1mA
0.15
0.4
V
VOLat IOL = 1mA
0.15
0.4
V
POWER BLOCKS
Upper Device rDS(ON)
VIN = 3V, 0.4A Per Power Block, Test Mode (Note 15)
122
215
346
m
Lower Device rDS(ON)
VIN = 3V, 0.4A Per Power Block, Test Mode (Note 15)
77
146
236
m
LXx Output Leakage
VIN = 5.5V, EN = LXx = GND, Single LXx Output
-1
0
VIN = 5.5V, EN = GND, LXx = VIN, Single LXx Output
0
15
µA
5
ns
VIN = 3.3V, VOUT = 1.8V, IOUT = 3A
90
%
VIN = 5V, VOUT = 2.5V, IOUT = 3A
92
%
1.4
V
Deadtime
Within a Single Power Block or between Power Blocks
(Note 15)
Efficiency
1.7
µA
POWER-ON RESET
POR Select (PORSEL)
Input High Threshold
VIN - 0.5
1.2
0.5
V
POR Select (PORSEL) Input Leakage Current VIN = 5.5V, PORSEL = GND or VIN
Input Low Threshold
-1
0
1
µA
VIN POR
Rising Threshold, PORSEL = VIN
4.1
4.25
4.45
V
Hysteresis, PORSEL = VIN
225
325
425
mV
Rising Threshold, PORSEL = GND
2.65
2.8
2.95
V
90
175
260
mV
0.56
0.6
0.64
V
Hysteresis, PORSEL = GND
Enable (EN) Input Voltage
Rising/Falling Threshold
Enable (EN) Input Leakage Current
VIN = 5.5V, EN = GND or VIN
-3
0
3
µA
Enable (EN) Sink Current
EN = 0.3V
6.4
11
16.6
µA
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FN8365.2
May 20, 2014
ISL70001ASEH
Electrical Specifications
Unless otherwise noted, VIN = AVDD = DVDD = PVINx = EN = M/S = 3V or 5.5V;
GND = AGND = DGND = PGNDx = TDI = TDO = ZAP = 0V; FB = 0.65V; PORSEL = VIN for 4.5V ≤ VIN ≤ 5.5V and GND for VIN < 4.5V,
SYNC = LXx = Open Circuit; PGOOD is pulled up to VIN with a 1k resistor; REF is bypassed to GND with a 220nF capacitor; SS is bypassed to GND with a
100nF capacitor; IOUT = 0A; TA = TJ = +25°C (Note 12). Boldface limits apply across the operating temperature range, -55°C to +125°C; over a total
iodizing dose of 100krad(Si) with exposure at a high dose rate of 50 - 300krad(Si)/s; and over a total iodizing dose of 50krad(Si) with exposure at a low
dose rate of <10mrad(Si)/s. (Continued)
MIN
(Note 13)
TYP
(Note 12)
MAX
(Note 13)
UNITS
20
23
27
µA
Soft-Start Discharge ON-Resistance
2.2
4.7

Soft-Start Discharge Time
256
PARAMETER
TEST CONDITIONS
SOFT-START
Soft-Start Source Current
SS = GND
Clock Cycles
POWER-GOOD SIGNAL
Rising Threshold
VFB as a % of VREF, Test Mode
107
111
115
%
Rising Hysteresis
VFB as a % of VREF, Test Mode
2
3.5
5
%
Falling Threshold
VFB as a % of VREF, Test Mode
85
89
93
%
Falling Hysteresis
VFB as a % of VREF, Test Mode
2
3.5
5
%
Power-Good Drive
VIN = 3V, PGOOD = 0.4V, EN = GND
7.3
8.2
Power-Good Leakage
VIN = PGOOD = 5.5V
mA
0.001
1
µA
PROTECTION FEATURES
Undervoltage Monitor
Undervoltage Trip Threshold
VIN = 3V, VFB as a % of VREF, Test mode
71
75
79
%
Undervoltage Recovery Threshold
VIN = 3V, VFB as a % of VREF, Test mode
84
88
92
%
Overcurrent Trip Level
LX4 Power Block, Test Mode, (Note 16)
1.3
1.9
2.5
A
Overcurrent Trip Counts
LX4 Power Block, Test Mode (Note 15)
Overcurrent or Short-Circuit Duty-Cycle
VIN = 3V, SS interval = 200µs, Test Mode, Fault
interval divided by hiccup interval
5
%
Overcurrent Monitor
2
0.8
NOTES:
10. L = 1µH connected to Lx.
11. 1kΩ PGOOD pull-up resistor is not populated.
12. Typical values shown are not guaranteed. Guaranteed min/max values are provided in the SMD.
13. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.
14. Limits do not include tolerance of external feedback resistors. The 0A to 6A output current range may be reduced by Minimum LXx On Time and
Minimum LXx Off Time specifications.
15. Limits established by design, characterization or analysis and are not production tested.
16. During an output short-circuit, peak current through the power block(s) can continue to build beyond the overcurrent trip level by up to 3A. With all
six power blocks connected, peak current through the power blocks and output inductor could reach (6 x 2.5A) + 3A = 18A.
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FN8365.2
May 20, 2014
ISL70001ASEH
Typical Operating Performance
100
100
95
95
EFFICIENCY (%)
EFFICIENCY (%)
Unless otherwise noted, TA = +25°C, VIN = 5V, EN = 5V, L = 1.0µH, CIN = 4x47µF, COUT = 10x100µF, VOUT = 1.8V, IOUT = 0A to 6A.
90
85
1.5V
1.8V
80
1.2V
2.5V
85
1.5V
1.8V
1.2V
0
1
2
3
4
5
70
6
0
1
2
2.0
1.8
1.8
1.6
1.6
POWER DISSIPATION (W)
POWER DISSIPATION (W)
2.0
2.5V
1.2
4
5
6
FIGURE 6. EFFICIENCY vs LOAD, VIN = 5.0V
FIGURE 5. EFFICIENCY vs LOAD, VIN = 3.3V
1.4
3
ILOAD (A)
ILOAD (A)
1.2V
1.8V
1.0
1.5V
0.8
0.6
0.4
2.5V
1.4
1.8V
1.2
1.2V
3.3V
1.0
1.5V
0.8
0.6
0.4
0.2
0.2
0
3.3V
2.5V
80
75
75
70
90
0
1
2
3
4
5
0
6
0
1
2
ILOAD (A)
3
4
5
6
ILOAD (A)
FIGURE 7. POWER DISSIPATION vs LOAD, VIN = 3.3V
FIGURE 8. POWER DISSIPATION vs LOAD, VIN = 5.0V
0.010
0.005
0.004
0.003
0.005
1.5V
0.001
1.2V
1.2V
VOUT (V)
VOUT (V)
0.002
0
-0.001
-0.002
-0.005
-0.003
1.8V
1.8V
-0.004
-0.005
1.5V
0
2.5V
0
1
2
3
ILOAD (A)
4
5
6
FIGURE 9. VOUT REGULATION vs ILOAD, VIN = 3.3V (NORMALIZED
to ILOAD = 0)
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2.5V
3.3V
-0.010
0
1
2
3
4
5
6
ILOAD (A)
FIGURE 10. VOUT REGULATION vs ILOAD, VIN = 5.0V (NORMALIZED
to ILOAD = 0)
FN8365.2
May 20, 2014
ISL70001ASEH
Typical Operating Performance
Unless otherwise noted, TA = +25°C, VIN = 5V, EN = 5V, L = 1.0µH, CIN = 4x47µF, COUT = 10x100µF, VOUT = 1.8V, IOUT = 0A to 6A. (Continued)
EN 2V/DIV
EN 2V/DIV
VOUT 1V/DIV
VOUT 1V/DIV
IL 1A/DIV
IL 2A/DIV
PGOOD 5V/DIV
PGOOD 5V/DIV
FIGURE 11. SOFT-START WITH NO LOAD
LX PULSE 2V/DIV
VOUT 20mV/DIV
IL 1A/DIV
FIGURE 13. STEADY STATE OPERATION WITH NO LOAD
VOUT 20mV/DIV
FIGURE 12. SOFT-START WITH FULL LOAD
LX PULSE 2V/DIV
IL 2A/DIV
VOUT 20mV/DIV
FIGURE 14. STEADY STATE OPERATION WITH FULL LOAD
VOUT 50mV/DIV
IL 2A/DIV
IL 2A/DIV
FIGURE 15. LOAD TRANSIENT 50%
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FIGURE 16. LOAD TRANSIENT 100%
FN8365.2
May 20, 2014
ISL70001ASEH
Typical Operating Performance
Unless otherwise noted, TA = +25°C, VIN = 5V, EN = 5V, L = 1.0µH, CIN = 4x47µF, COUT = 10x100µF, VOUT = 1.8V, IOUT = 0A to 6A. (Continued)
EN 2V/DIV
EN 2V/DIV
VOUT 1V/DIV
VOUT 1V/DIV
IL 1A/DIV
IL 2A/DIV
PGOOD 5V/DIV
PGOOD 5V/DIV
FIGURE 17. SOFT-START WITH PRE-BIASED 0.5V
FIGURE 18. SOFT-DISCHARGE SHUTDOWN
LX 5V/DIV
LX 5V/DIV
VOUT 1V/DIV
VOUT 1V/DIV
IL 5A/DIV
IL 5A/DIV
PGOOD 5V/DIV
PGOOD 5V/DIV
FIGURE 19. OUTPUT SHORT CIRCUIT
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FIGURE 20. OUTPUT SHORT CIRCUIT RECOVERY
FN8365.2
May 20, 2014
ISL70001ASEH
Functional Description
The ISL70001ASEH is a monolithic, fixed frequency,
current-mode synchronous buck regulator with user configurable
power blocks. Two ISL70001ASEH devices can be used to provide
a total DC/DC solution for FPGAs, CPLDs, DSPs and CPUs.
The ISL70001ASEH utilizes peak current-mode control with
integrated compensation and switches at a fixed frequency of
1MHz. Two ISL70001ASEH devices can be synchronized 180°
out-of-phase to reduce input RMS ripple current. These attributes
reduce the number and size of external components required,
while providing excellent output transient response. The
internal synchronous power switches are optimized for high
efficiency and good thermal performance.
six LXx pins to the output inductor provides a maximum 6A of
output current. See the “Typical Application Schematic” on
page 5 for pin connection guidance.
A scaled pilot device associated with each power block provides
current feedback. Power block 4 contains the master pilot device
and this is why it must be connected to the output inductor.
Main Control Loop
During normal operation, the internal top power switch is turned
on at the beginning of each clock cycle. Current in the output
inductor ramps up until the current comparator trips and turns
off the top power MOSFET. The bottom power MOSFET turns on
and the inductor current ramps down for the rest of the cycle.
The chip features a comparator type enable input that provides
flexibility. It can be used for simple digital on/off control or,
alternately, can provide undervoltage lockout capability by
using two external resistors to precisely sense the level of an
external supply voltage. A power-good signal indicates when the
output voltage is within ±11% typical of the nominal output
voltage.
The current comparator compares the output current at the
ripple current peak to a current pilot. The error amplifier monitors
VOUT and compares it with an internal reference voltage. The
output voltage of the error amplifier drives a proportional current
to the pilot. If VOUT is low, the current level of the pilot is
increased and the trip off current level of the output is increased.
The increased output current raises VOUT until it is in agreement
with the reference voltage.
Regulator start-up is controlled by an analog soft-start circuit,
which can be adjusted from approximately 2ms to 200ms by
using an external capacitor.
Output Voltage Selection
The ISL70001ASEH differs from the ISL70001SEH in the fault
counts needed to initiate an overcurrent or undervoltage
condition. The ISL70001ASEH also has a lower standby supply
current.
Power Blocks
The power output stage of the regulator consists of six 1A
capable power blocks that are paralleled to provide full 6A
output current capability. The block diagram in Figure 21 shows
a top level view of the individual power blocks.
The output voltage of the ISL70001ASEH can be adjusted using
an external resistor divider as shown in Figure 22.
VREF = 0.6V
CREF = 220nF
RT = 1k
CC = 4.7nF
POWER BLOCK 1
PVIN2
LX2
PGND2
POWER BLOCK 2
POWER BLOCK 5
PVIN5
LX5
PGND5
PVIN3
LX3
PGND3
POWER BLOCK 3
POWER BLOCK 4
PVIN4
LX4
PGND4
POWER BLOCK 6
PVIN6
LX6
PGND6
FIGURE 21. POWER BLOCK DIAGRAM
Each power block has a power supply input pin, PVINx, a phase
output pin, LXx, and a power supply ground pin, PGNDx. All PVINx
pins must be connected to a common power supply rail and all
PGNDx pins must be connected to a common ground. LXx pins
should be connected to the output inductor based on the
required load current, but must include the LX4 pin. For example,
if 3A of output current is needed, any three LXx pins can be
connected to the inductor as long as one of them is the LX4 pin.
The unused LXx pins should be left unconnected. Connecting all
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VOUT
COUT
CC
RT
ERROR
AMPLIFIER
FB
+
PVIN1
LX1
PGND1
L
LXx OUT
VREF
REF
RB
CREF
FIGURE 22. OUTPUT VOLTAGE SELECTION
RT should be selected as 1kto mitigate SEE. RT should be
shunted by a 4.7nF ceramic capacitor, CC, to mitigate SEE and to
improve loop stability margins. The REF pin should be bypassed
to AGND with a 220nF ceramic capacitor to mitigate SEE. It
should be noted that no current (sourcing or sinking) is available
from the REF pin. RB can be determined from Equation 3. The
designer can configure the output voltage from 0.8V to 85% of
the input voltage.
V REF
R B = R T  -------------------------------V
–V
OUT
(EQ. 3)
REF
Switching Frequency/Synchronization
The ISL70001ASEH features an internal oscillator running at a
fixed frequency of 1MHz ±15% over recommended operating
conditions. The regulator can be configured to run from the
internal oscillator or can be synchronized to another
ISL70001ASEH or an SEE hardened external clock with a
frequency range of 1MHz ±20%.
FN8365.2
May 20, 2014
ISL70001ASEH
To run the regulator from the internal oscillator, connect the M/S
pin to DVDD. In this case, the output of the internal oscillator
appears on the SYNC pin. To synchronize the regulator to the
SYNC output of another ISL70001ASEH regulator or to an SEE
hardened external clock, connect the M/S pin to DGND. In this
case, the SYNC pin is an input that accepts an external
synchronizing signal. When synchronizing multiple devices, Slave
regulators are synchronized 180° out-of-phase with respect to
the SYNC output of a Master regulator or to an external clock.
VR = 0.6V
IEN = 11µA
CEN = 10nF
PVINx
VIN2
ENABLE
COMPARATOR
Operation Initialization
The ISL70001ASEH initializes based on the state of the power-on
reset (POR) monitor of the PVINx inputs and the state of the EN
input. Successful initialization prompts a soft-start interval, and
the regulator begins slowly ramping the output voltage. Once the
commanded output voltage is within the proper window of
operation, the power-good signal changes state from low-to-high,
indicating proper regulator operation.
R1
EN
+
-
POR
LOGIC
CEN
VR
R2
IEN
Power-On Reset
FIGURE 23. ENABLE CIRCUIT
The POR circuitry prevents the controller from attempting to
soft-start before sufficient bias is present at the PVINx pins.
The POR threshold of the PVINx pins is controlled by the PORSEL
pin. For a nominal 5V supply voltage, PORSEL should be
connected to DVDD. For a nominal 3.3V supply voltage, PORSEL
should be connected to DGND. For nominal supply voltages
between 5V and 3.3V, PORSEL should be connected to DGND.
The POR rising and falling thresholds are shown in the “Electrical
Specifications” table on page 8.
Hysteresis between the rising and falling thresholds ensures that
small perturbations on PVINx seen during turn-on/turn-off of the
regulator do not cause inadvertent turn-off/turn-on of the
regulator. When the PVINx pins are below the POR rising
threshold, the internal synchronous power MOSFET switches are
turned off, and the LXx pins are held in a high-impedance state.
Enable and Disable
After the POR input requirement is met, the ISL70001ASEH
remains in shutdown until the voltage at the enable input rises
above the enable threshold. As shown in Figure 23, the enable
circuit features a comparator type input. In addition to simple
logic on/off control, the enable circuit allows the level of an
external voltage to precisely gate the turn-on/turn-off of the
regulator. An internal IEN current sink with a typical value of
11µA is only active when the voltage on the EN pin is below the
enable threshold. The current sink pulls the EN pin low. As VIN2
rises, the enable level is not set exclusively by the resistor divider
from VIN2.
With the current sink active, the enable level is defined by
Equation 4. R1 is the resistor from the EN pin to VIN2 and R2 is
the resistor from the EN pin to the AGND pin.
R1
V ENABLE = V R  1 + ------- + I EN  R 1
R
2
14
With the part enabled and the IEN current sink off, the disable
level is set by the resistor divider. The disable level is defined by
Equation 5.
R1
V DISABLE = V R  1 + ------R2
(EQ. 5)
The difference between the enable and disable levels provides
adjustable hysteresis so that noise on VIN2 does not interfere
with the enabling or disabling of the regulator.
To mitigate SEE, the EN pin should be bypassed to the AGND pin
with a 10nF ceramic capacitor.
Soft-Start
Once the POR and enable circuits are satisfied, the regulator
initiates a soft-start. Figure 24 shows that the soft-start circuit
clamps the error amplifier reference voltage to the voltage on an
external soft-start capacitor connected to the SS pin.
VREF = 0.6V
ISS = 23µA
RD = 2.2Ω
VOUT
RT
FB
RB
ERROR
AMPLIFIER
PWM
LOGIC
+
+
SS
REF
VREF
CSS
CREF
RD
ISS
(EQ. 4)
Once the voltage at the EN pin reaches the enable threshold, the
IEN current sink turns off.
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VIN1
FIGURE 24. SOFT-START CIRCUIT
FN8365.2
May 20, 2014
ISL70001ASEH
The soft-start capacitor is charged by an internal ISS current
source. As the soft-start capacitor is charged, the output voltage
slowly ramps to the set point determined by the reference
voltage and the feedback network. Once the voltage on the SS
pin is equal to the internal reference voltage, the soft-start
interval is complete. The controlled ramp of the output voltage
reduces the in-rush current during start-up. The soft-start output
ramp interval is defined in Equation 6 and is adjustable from
approximately 2ms to 200ms. The value of the soft-start
capacitor, CSS, should range inclusively from 8.2nF to 8.2µF. The
peak in-rush current can be computed from Equation 7. The
soft-start interval should be long enough to ensure that the peak
in-rush current plus the peak output load current does not exceed
the overcurrent trip level of the regulator.
V REF
t SS = C SS  ------------I
(EQ. 6)
SS
V OUT
I INRUSH = C OUT  ------------t
(EQ. 7)
SS
The soft-start capacitor is immediately discharged by a 2.2
resistor whenever POR conditions are not met or EN is pulled low.
The soft-start discharge time is equal to 256 clock cycles.
Power-Good
The power-good (PGOOD) pin is an open-drain logic output that
indicates when the output voltage of the regulator is within
regulation limits. The power-good pin pulls low during shutdown
and remains low when the controller is enabled. After a
successful soft-start, the PGOOD pin releases, and the voltage
rises with an external pull-up resistor. The power-good signal
transitions low immediately when the EN pin is pulled low.
The power-good circuitry monitors the FB pin and compares it to
the rising and falling thresholds shown in the “Electrical
Specifications” table on page 9. If the feedback voltage exceeds
the typical rising limit of 111% of the reference voltage, the
PGOOD pin pulls low. The PGOOD pin continues to pull low until
the feedback voltage falls to a typical of 107.5% of the reference
voltage. If the feedback voltage drops below a typical of 89% of
the reference voltage, the PGOOD pin pulls low. The PGOOD pin
continues to pull low until the feedback voltage rises to a typical
92.5% of the reference voltage. The PGOOD pin then releases
and signals the return of the output voltage to within the
power-good window.
The PGOOD pin can be pulled up to any voltage from 0V to 5.5V,
independently from the supply voltage. The pull-up resistor
should have a nominal value from 1k to 10k. The PGOOD pin
should be bypassed to DGND, with a 10nF ceramic capacitor to
mitigate SEE.
Fault Monitoring and Protection
The ISL70001ASEH actively monitors output voltage and current
to detect fault conditions. Fault conditions trigger protective
measures to prevent damage to the regulator and external load
device.
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Undervoltage Protection
A hysteretic comparator monitors the FB pin of the regulator. The
feedback voltage is compared to an undervoltage threshold that
is a fixed percentage of the reference voltage. Once the
comparator trips, indicating a valid undervoltage condition, an
undervoltage counter increments. The counter is reset if the
feedback voltage rises back above the undervoltage threshold,
plus a specified amount of hysteresis outlined in the “Electrical
Specifications” table on page 9. If the undervoltage condition
exists for 3 consecutive counts, the counter overflows and the
undervoltage protection logic shuts down the regulator.
After the regulator shuts down, it enters a delay interval
equivalent to the soft-start interval, which allows the device to
cool. The undervoltage counter is reset when the device enters
the delay interval. The protection logic initiates a normal
soft-start once the delay interval ends. If the output successfully
soft-starts, the power-good signal goes high, and normal
operation continues. If undervoltage conditions continue to exist
during the soft-start interval, the undervoltage counter must
overflow before the regulator shuts down again. This hiccup
mode continues indefinitely until the output soft-starts
successfully.
Overcurrent Protection
A pilot device integrated into the PMOS transistor of Power Block 4
samples current each cycle. This current feedback is scaled and
compared to an overcurrent threshold based on the number of
power blocks connected. Each additional power block connected
beyond Power Block 4 increases the overcurrent limit by 2A. For
example, if three power blocks are connected, the typical current
limit threshold would be 3 x 2A = 6A.
If the sampled current exceeds the overcurrent threshold, an
overcurrent counter increments by one. Once the overcurrent
counter reaches a count of 3, it overflows and the regulator shuts
down. If the sampled current falls below the threshold before the
counter overflows, the counter is reset.
After the regulator shuts down, it enters a delay interval,
equivalent to the soft-start interval, which allows the device to
cool. The overcurrent counter is reset when the device enters the
delay interval. The protection logic initiates a normal soft-start
once the delay interval ends. If the output successfully
soft-starts, the power-good signal goes high, and normal
operation continues. If overcurrent conditions continue to exist
during the soft-start interval, the overcurrent counter must
overflow before the regulator shuts down the output again. This
hiccup mode continues indefinitely until the output soft-starts
successfully.
NOTE: To prevent severe negative ringing that can disturb the overcurrent
counter, it is recommended that a Schottky diode of appropriate rating be
added from the LXx pins to the PGNDx pins.
Feedback Loop Compensation
To reduce the number of external components and to simplify the
process of determining compensation components, the
ISL70001ASEH buck regulator has an internally compensated
error amplifier.
FN8365.2
May 20, 2014
ISL70001ASEH
Due to the current loop feedback in peak current mode control, the
modulator has a single pole response with -20dB slope at a
frequency determined by the load (Equation 8):
1
F PO = ------------------------------------2  R O  C OUT
(EQ. 8)
where RO is load resistance and COUT is the output load
capacitance. For this type of modulator, a Type 2 compensation
circuit is usually sufficient.
Figure 25 shows a Type 2 amplifier and its response, along with
the responses of the current mode modulator and the converter.
C2
R2
C1
CONVERTER
R1
EA
TYPE 2 EA
FZ
FPO
FIGURE 25. FEEDBACK LOOP COMPENSATION
The Type 2 amplifier, in addition to the pole at origin, has a
zero-pole pair that causes a flat gain region at frequencies
between the zero and the pole (Equations 9 and 10).
(EQ. 9)
1
F P = ------------------------------ = 546kHz
2  R 1  C 2
(EQ. 10)
Zero frequency and amplifier high-frequency gain were chosen to
satisfy typical applications. The crossover frequency will appear
at the point where the modulator attenuation equals the
amplifier high frequency gain. The only task that the system
designer has to complete is to specify the output filter capacitors
to position the load main pole somewhere within one decade
lower than the amplifier zero frequency. Equation 13 on page 17
approximates the amount of capacitance needed to achieve an
optimal pole location depending on the number of LXx pins
connected. With this type of compensation, plenty of phase
margin is easily achieved due to zero-pole pair phase ‘boost’.
Conditional stability may occur only when the main load pole is
positioned too much to the left side on the frequency axis due to
excessive output filter capacitance. In this case, the ESR zero
placed within the 1.2kHz to 30kHz range gives some additional
phase ‘boost’. Some phase boost is also achieved by connecting
the recommended capacitor CC in parallel with the upper resistor
RT of the divider that sets the output voltage value, as
demonstrated in Figure 22.
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Output Filter Design
The output inductor and the output capacitor bank together form
a low-pass filter responsible for smoothing the pulsating voltage
at the phase node. The filter must also provide the transient
energy until the regulator can respond. Since the filter has low
bandwidth relative to the switching frequency, it limits the
system transient response. The output capacitors must supply or
sink current while the current in the output inductor increases or
decreases to meet the load demand.
The critical load parameters in choosing the output capacitors are
the maximum size of the load step (ISTEP), the load-current slew
rate (di/dt), and the maximum allowable output voltage deviation
under transient loading (VMAX). Capacitors are characterized
according to their capacitance, Equivalent Series Resistance (ESR)
and Equivalent Series Inductance (ESL).
FP
FC
1
F Z = ------------------------------ = 8.6kHz
2  R 2  C 1
This design guide is intended to provide a high-level explanation
of the steps necessary to create a power converter. It is assumed
the reader is familiar with many of the basic skills and
techniques referenced in the following. In addition to this guide,
Intersil provides a complete evaluation board that includes
schematic, BOM, and an example PCB layout (see “Ordering
Information” table on page 2).
OUTPUT CAPACITOR SELECTION
GEA = 25.1dB
MODULATOR
Component Selection Guide
At the beginning of a load transient, the output capacitors supply all
of the transient current. The output voltage initially deviates by an
amount approximated by the voltage drop across the ESL. As the
load current increases, the voltage drop across the ESR increases
linearly until the load current reaches its final value. Neglecting the
contribution of inductor current and regulator response, the output
voltage initially deviates by an amount shown in Equation 11.
di
V MAX  ESL  ----- +  ESR  I STEP 
dt
(EQ. 11)
The filter capacitors selected must have sufficiently low ESL and
ESR such that the total output voltage deviation is less than the
maximum allowable ripple.
Most capacitor solutions rely on a mixture of high frequency
capacitors with relatively low capacitance in combination with
bulk capacitors having high capacitance but larger ESR.
Minimizing the ESL of the high-frequency capacitors allows them
to support the output voltage as the current increases.
Minimizing the ESR of the bulk capacitors allows them to supply
the increased current with less output voltage deviation.
Ceramic capacitors with X7R dielectric are recommended.
Alternately, a combination of low ESR solid tantalum capacitors
and ceramic capacitors with X7R dielectric may be used.
The ESR of the bulk capacitors is responsible for most of the
output voltage ripple. As the bulk capacitors sink and source the
inductor AC ripple current, a voltage, VP-P(MAX), develops across
the bulk capacitor according to Equation 12.
 V IN – V OUT V OUT
V P-P(MAX) = ESR  ---------------------------------------------L OUT  f s  V IN
(EQ. 12)
FN8365.2
May 20, 2014
ISL70001ASEH
In addition to ESL and ESR, another consideration in selecting
the output capacitors is loop stability. The total output
capacitance sets the dominant pole of the PWM. Because the
ISL70001ASEH uses integrated compensation techniques, it is
necessary to restrict the output capacitance in order to optimize
loop stability. The recommended load capacitance can be
estimated using Equation 13.
1.8V
C OUT = 75F  Number of LXx Pins Connected  ------------V OUT
(EQ. 13)
Another stability requirement on the selection of the output
capacitor is that the ‘ESR zero’ (f ZESR) be placed at 60kHz to
90kHz. This range is set by an internal, single compensation zero
at 8.6kHz. This ESR zero location contributes to an increased
phase margin of the control loop; therefore if a capacitor is
chosen with an inadequate ESR, stability may be compromised.
Equation 14 may be used to calculate the required ESR to place
the ‘ESR zero’ in the recommended range:
1
ESR = ---------------------------------------------2  f ZESR   C OUT 
(EQ. 14)
2  C OUT
L OUT  ------------------------- V MAX –  I L(P-P)  ESR   V IN – V OUT


 I STEP  2
Another concern when selecting an output inductor is to ensure
there is adequate slope compensation when the regulator is
operated above 50% duty cycle. Since the internal slope
compensation is fixed, output inductance should satisfy
Equation 18 to ensure this requirement is met.
4.32µH
L OUT  ------------------------------------------------------------------------------Number of LXx Pins Connected
2. The ESR must be sufficiently low to meet the desired output
voltage ripple due to the output inductor current.
3. The ESR zero should be placed, in a rather large range, to
provide additional phase margin.
OUTPUT INDUCTOR SELECTION
Once the output capacitors are selected, the maximum allowable
ripple voltage, VP-P(MAX), determines the lower limit on the
inductance as shown in Equation 15.
 V IN – V OUT V OUT
L OUT  ESR  -------------------------------------------------f s  V IN  V P-P(MAX)
(EQ. 15)
Since the output capacitors are supplying a decreasing portion of
the load current while the regulator recovers from the transient,
the capacitor voltage becomes slightly depleted. The output
inductor must be capable of assuming the entire load current
before the output voltage decreases more than VMAX. This
places an upper limit on inductance.
Equation 16 gives the upper limit on output inductance for the
case when the trailing edge of the current transient causes a
greater output voltage deviation than the leading edge.
Equation 17 addresses the leading edge. Normally, the trailing
edge dictates the inductance selection because duty cycles are
usually <50%. Nevertheless, both inequalities should be
evaluated, and inductance should be governed based on the
lower of the two results. In each equation, LOUT is the output
inductance, COUT is the total output capacitance, and IL(P-P) is
the peak-to-peak ripple current in the output inductor.
2  C OUT  V OUT
L OUT  --------------------------------------V MAX –  I L(P-P)  ESR 
 I STEP  2
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17
(EQ. 18)
Input Capacitor Selection
Input capacitors are responsible for sourcing the AC component
of the input current flowing into the switching power devices.
Their RMS current capacity must be sufficient to handle the AC
component of the current drawn by the switching power devices,
which is related to duty cycle. The maximum RMS current
required by the regulator is closely approximated by Equation 19.
I RMS
MAX
=
V OUT 
2 1  V IN – V OUT V OUT 2
-----------------   I
+ ------   ----------------------------------  ----------------- 
V IN
12  L
V IN  
 OUT  MAX 
OUT  f s
(EQ. 19)
In conclusion, the output capacitors must meet three criteria:
1. They must have sufficient bulk capacitance to sustain the
output voltage during a load transient while the output
inductor current is slewing to the value of the load transient.
(EQ. 17)
The important parameters to consider when selecting an input
capacitor are the voltage rating and the RMS ripple current
rating. For reliable operation, select capacitors with voltage
ratings at least 1.5x greater than the maximum input voltage.
The capacitor RMS ripple current rating should be higher than
the largest RMS ripple current required by the circuit.
Ceramic capacitors with X7R dielectric are recommended.
Alternately, a combination of low ESR solid tantalum capacitors
and ceramic capacitors with X7R dielectric may be used. The
ISL70001ASEH requires a minimum effective input capacitance
of 100µF for stable operation.
Derating Current Capability
Most space programs issue specific derating guidelines for parts,
but these guidelines take the pedigree of the part into account.
For instance, a device built to MIL-PRF-38535, such as the
ISL70001ASEH, is already heavily derated from a current density
standpoint. However, a mil-temp or commercial IC that is
up-screened for use in space applications may need additional
current derating to ensure reliable operation because it was not
built to the same standards as the ISL70001ASEH.
Figure 26 shows the maximum average output current of the
ISL70001ASEH with respect to junction temperature. These plots
take into account the worst-case current share mismatch in the
power blocks and the current density requirement of
MIL-PRF-38535 (< 2 x 105 A/cm2). The plot clearly shows that
the ISL70001ASEH can handle 12.1A at +125°C from a
worst-case current density standpoint, but the part is limited to
7.8A because that is the lower limit of the current limit threshold
with all six power blocks connected.
(EQ. 16)
FN8365.2
May 20, 2014
MAXIMUM AVERAGE CURRENT FOR
0.1% FAILURES AT 100,000 HOURS (A)
ISL70001ASEH
13
12
11
3A
10.18
10
9
MINIMUM OCP
LEVEL = 7.8A
8.57
8
ERROR
AMPLIFIER
6.16
6
5.3
+
125
130
135
140
145
150
COUT
RT
PGNDx
CC
FB
-
6A AT +146°C
5
RS
VOUT
CS
7.25
7
4
120
LOUT
LXx
12.14
VREF
RB
REF
CREF
155
JUNCTION TEMPERATURE (°C)
FIGURE 26. CURRENT vs TEMPERATURE
FIGURE 27. SCHOTTKY DIODE AND R-C SNUBBER
PCB Layout
PCB Design
PCB design is critical to high-frequency switching regulator
performance. Careful component placement and trace routing
are necessary to reduce voltage spikes and minimize
undesirable voltage drops. Selection of a suitable thermal
interface material is also required for optimum heat dissipation
and to provide lead strain relief. See Table 1 on page 20 for
layout x-y coordinates.
Use a small island of copper to connect the LXx pins of the IC to
the output inductor on Layers 1 and 4. To minimize capacitive
coupling to the power and ground planes, void the copper on
Layers 2 and 3 adjacent to the island. Place most of the island of
Layer 4 to minimize the amount of copper that must be voided
from the ground plane (Layer 2).
Keep all other signal traces as short as possible.
PCB Plane Allocation
For an example layout, see AN1842.
Four layers of 2-oz. copper are recommended. Layer 2 should be
a dedicated ground plane with all critical component ground
connections made with vias to this layer. Layer 3 should be a
dedicated power plane split between the input and output power
rails. Layers 1 and 4 should be used primarily for signals but can
also provide additional power and ground islands, as required.
Thermal Management for Ceramic Package
PCB Component Placement
Components should be placed as close as possible to the IC to
minimize stray inductance and resistance. Prioritize the
placement of bypass capacitors on the pins of the IC in the order
shown: REF, SS, AVDD, DVDD, PVINx (high frequency capacitors),
EN, PGOOD, PVINx (bulk capacitors).
Locate the output voltage resistive divider as close as possible to
the FB pin of the IC. The top leg of the divider should connect
directly to the POL (Point of Load), and the bottom leg of the
divider should connect directly to AGND. The junction of the
resistive divider should connect directly to the FB pin.
Locate a Schottky clamp diode as close as possible to the LXx
and PGNDx pins of the IC. A small series R-C snubber connected
from the LXx pins to the PGNDx pins may be used to damp high
frequency ringing on the LXx pins, if desired, see Figure 27.
For optimum thermal performance, place a pattern of vias and a
thermal land on the top layer of the PCB directly underneath the
IC. Connect the vias to the plane which serves as a heatsink. To
ensure good thermal contact, thermal interface material such as
a Sil-Pad or thermally conductive epoxy should be used to fill the
gap between the vias and the bottom of the ceramic package.
Lead Strain Relief
The package leads protrude from the bottom of the package and
the leads need forming to provide strain relief. On the ceramic
bottom package R48.A, the Sil-pad or epoxy maybe be used to fill
the gap left between the PCB board and the bottom of the
package when lead forming is completed. On the heatsink option
of the package, R48.B, the lead forming should be made so that
the bottom of the heatsink and the formed leads are flush.
Heatsink Mounting Guidelines
The R48.B package option has a heatsink mounted on the
underside of the package. The following JESD51-5 guidelines
may be used to mount the package:
1. Place a thermal land on the PCB under the heatsink.
2. The land should be approximately the same size as to 1mm
larger than the 9x9mm heatsink.
3. Place an array of thermal vias below the thermal land.
- Via array size: ~8x8=64 thermal vias
- Via diameter: ~0.3mm drill diameter with plated copper on
the inside of each via.
- Via pitch: ~1.2mm.
- Vias should drop to and contact as much buried metal area
as feasible to provide the best thermal relief.
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18
FN8365.2
May 20, 2014
ISL70001ASEH
Heatsink Electrical Potential
The heatsink is electrically isolated and unbiased. The heatsink
may be electrically connected to any potential which offers the
best thermal relief through conductive mounting materials
(conductive epoxy, solder, etc) or may be left unbiased through
the use of electrically non-conductive mounting materials
(non-conductive epoxy, Sil-pad, kapton film, etc.).
Weight Characteristics
Weight of Packaged Device
1.602 Grams typical - R48.A Package
2.440 Grams typical - R48.B Package
Die Characteristics
Die Dimensions
5720µm x 5830µm (225.2 mils x 229.5 mils)
Thickness: 483µm ± 25.4µm (19.0 mils ± 1 mil)
Interface Materials
Silicon
ASSEMBLY RELATED INFORMATION
Substrate Potential Package R48.A and R48.B
PGND
Metal Lid Potential
Electrically Isolated -Package R48.A
PGND - Package R48.B
ADDITIONAL INFORMATION
GLASSIVATION
Worst Case Current Density
Type: Silicon Oxide and Silicon Nitride
Thickness: 0.3µm ± 0.03µm to 1.2µm ± 0.12µm
TOP METALLIZATION
Type: AlCu (0.5%)
Thickness: 2.7µm ±0.4µm
SUBSTRATE
< 2 x 105 A/cm2
Transistor Count
25030
Layout Characteristics
Step and Repeat
Type: Silicon
Isolation: Junction
Submit Document Feedback
BACKSIDE FINISH
5720µm x 5830µm
Connect PGND to PGNDx
19
FN8365.2
May 20, 2014
ISL70001ASEH
Metallization Mask Layout
ISL70001ASEH
LX1
SYNC PVIN1
PGND1
PGND2
LX2
PVIN2
PVIN3
M/S
ZAP
LX3
TDI
TDO
PGND3
PGOOD
PGND4
SS
LX4
DVDD
PVIN4
PVIN5
DGND
PGND
LX5
AGND
AVDD
REF
FB
EN PORSEL
PVIN6
LX6
PGND6
PGND5
ORIGIN
TABLE 1. LAYOUT X-Y COORDINATES
PAD NUMBER
X
(µm)
Y
(µm)
dX
(µm)
dY
(µm)
BOND WIRES
PER PAD
AVDD
15
478
263
135
135
1
REF
16
865
263
135
135
1
FB
17
1295
263
135
135
1
EN
18
1751
263
135
135
1
PORSEL
19
2151
263
135
135
1
PVIN6
20
2838
188
521
135
3
LX6
21
3449
188
521
135
3
PGND6
22
4060
188
521
135
3
PGND5
23
4845
188
521
135
3
LX5
24
5449
925
135
521
3
PVIN5
25
5449
1651
135
521
3
PVIN4
26
5449
2263
135
521
3
LX4
27
5449
2874
135
521
3
PAD NAME
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20
FN8365.2
May 20, 2014
ISL70001ASEH
TABLE 1. LAYOUT X-Y COORDINATES (Continued)
PAD NUMBER
X
(µm)
Y
(µm)
dX
(µm)
dY
(µm)
BOND WIRES
PER PAD
PGND4
28
5449
3485
135
521
3
PGND3
29
5449
4096
135
521
3
LX3
30
5449
4745
135
521
3
PVIN3
31
4941
5559
521
135
3
PVIN2
32
4137
5559
521
135
3
LX2
33
3449
5559
521
135
3
PGND2
34
2838
5559
521
135
3
PGND1
1
2227
5559
521
135
3
LX1
2
1578
5559
521
135
3
PVIN1
3
962
5559
521
135
3
SYNC
4
544
5559
135
135
1
M/S
5
226
5280
135
135
1
ZAP
6
226
4910
135
135
1
TDI
7
226
4540
135
135
1
TDO
8
226
4170
135
135
1
PGOOD
9
226
3777
135
135
1
SS
10
226
3425
135
135
1
DVDD
11
226
2566
135
333
2
DGND
12
226
1538
135
333
2
PGND
13
226
1018
135
135
1
AGND
14
226
654
135
135
1
PAD NAME
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21
FN8365.2
May 20, 2014
ISL70001ASEH
Revision History
The revision history provided is for informational purposes only and is believed to be accurate, but not warranted. Please go to web to
make sure you have the latest Rev.
DATE
REVISION
CHANGE
May 20, 2014
FN8365.2
Page 11: Figure 13 and 14, updated the LX Signal label from 5V/div to 2V/div.
February 26, 2014
FN8365.1
Added Note 10 “L = 1µH connected to Lx.” on page 9
Added Note 11 “1kΩ PGOOD pull-up resistor is not populated.” on page 9
Removed MSL note from the ordering information on page 2 as it is not applicable to Hermetic packages.
May 22, 2013
FN8365.0
Initial Release
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22
FN8365.2
May 20, 2014
ISL70001ASEH
Package Outline Drawing
R48.A
48 CERAMIC QUAD FLATPACK PACKAGE (CQFP)
Rev 3, 10/12
1.118 (28.40)
1.080 (27.43)
0.572 (14.53)
0.555 (14.10)
#1 #48
0.287 (7.29)
0.253 (6.43)
0.040 (1.02) BSC
PIN 1
INDEX AREA
0.572 (14.53)
0.555 (14.10)
1.118 (28.40)
1.080 (27.43)
0.007 (0.18) MIN
0.015 (0.38)
0.008 (0.20)
0.015 (0.38) MIN
TOP VIEW
0.099 (2.51)
0.076 (1.93)
0.016 (0.41)
0.009 (0.23)
SIDE VIEW
NOTE:
1. All dimensions are in inches (millimeters).
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23
FN8365.2
May 20, 2014
ISL70001ASEH
Package Outline Drawing
R48.B
48 CERAMIC QUAD FLATPACK PACKAGE (CQFP) WITH BOTTOM HEATSINK
Rev 0, 10/12
1.118 (28.40)
1.080 (27.43)
0.572 (14.53)
0.555 (14.10)
#1 #48
0.287 (7.29)
0.253 (6.43)
0.040 (1.016) BSC
PIN 1
INDEX AREA
1.118 (28.40)
1.080 (27.43)
0.572 (14.53)
0.555 (14.10)
0.012 (0.30)
0.008 (0.20)
TOP VIEW
0.131 (3.33)
0.105 (2.67)
0.042 (1.067) REF
0.026 (0.66) MIN. 2
0.013 (0.33)
0.009 (0.23)
HEATSINK
SIDE VIEW
0.359 (9.12)
0.349 (8.87)
HEATSINK
0.359 (9.12)
0.349 (8.87)
PIN 1
INDEX AREA
NOTES:
1. All dimensions are in inches (millimeters)
2. Dimension shall be measured at point of exit
(beyond the meniscus) of the lead from the body.
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24
#1 #48
BOTTOM VIEW
FN8365.2
May 20, 2014
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