DATASHEET
ISL91127
FN8418
Rev 5.01
Aug 26, 2022
High Efficiency Buck-Boost Regulator with 4.5A Switches
The ISL91127 is a high-current, buck-boost switching regulator
for systems using new battery chemistries. It uses the Renesas
proprietary buck-boost algorithm to maintain voltage
regulation while providing excellent efficiency and very low
output voltage ripple when the input voltage is close to the
output voltage.
Features
The ISL91127 can deliver at least 2.1A continuous output
current (VOUT = 3.3V) across a battery voltage range of 2.5V to
4.35V. This maximizes the energy utilization of advanced,
single-cell Li-ion battery chemistries that have significant
capacity left at voltages below the system voltage. Its fully
synchronous low ON-resistance 4-switch architecture and a low
quiescent current of only 30µA optimize efficiency under all
load conditions.
• Input voltage range: 1.8V to 5.5V
The ISL91127 supports stand-alone applications with a fixed
3.3V or 3.5V output voltage or adjustable output voltage with
an external resistor divider. Output voltages as low as 1V or as
high as 5.2V are supported.
• Fully protected for short-circuit, over-temperature, and
undervoltage
The ISL91127 is available in a 20 bump, 0.4mm pitch WLCSP
(2.15mmx1.74mm) with a 2.5MHz switching frequency, which
further reduces the size of external components.
Applications
• Accepts input voltages above or below regulated output
voltage
• Automatic and seamless transitions between Buck and
Boost modes
• Continuous output current: up to 2.1A (PVIN = 2.5V,
VOUT = 3.3V)
• High efficiency: up to 96%
• 30µA quiescent current maximizes light-load efficiency
• 2.5MHz switching frequency minimizes external component
size
• Small 2.15mmx1.74mm WLCSP
• Brownout-free system voltage for smartphones and tablet
PCs
• Wireless communication devices
• 2G/3G/4G RF power amplifiers
100
VIN = 3.6V
C1
10µF
LX1
PVIN
L1
1µH
LX2
VIN
VOUT
EN
MODE
FB
VOUT = 3.3V
C2
2x22µF
EFFICIENCY (%)
ISL91127IINZ
VIN = 1.8V TO 5.5V
VIN = 4V
95
90
85
VIN = 3.3V
VIN = 3V
VIN = 2.5V
80
SGND PGND
75
1
10
100
100 0
LOAD CURREN T (mA)
FIGURE 1. TYPICAL APPLICATION: VOUT = 3.3V
FN8418 Rev 5.01
Aug 26, 2022
FIGURE 2. EFFICIENCY: VOUT = 3.3V
Page 1 of 12
© 2016-2022 Renesas Electronics
ISL91127
Block Diagram
LX1
LX2
B1 B2 B3
D1 D2 D3
E1
A1
PVIN A2
E2 VOUT
A3
SOFT
DISCHARGE
REVERSE
CURRENT
GATE
DRIVERS
AND ANTISHOOT THRU
EN
EN
C1
EN
VIN A4
E3
C2 PGND
VREF
PVIN
MONITOR
THERMAL
SHUTDOWN
MODE C3
VOUT
CLAMP
PWM
CONTROL
CURRENT
DETECT
EN
EN B4
VOUT
MONITOR
EN
E4 FB
EN
SGND D4
OSC
REF
ERROR
AMP
C4
VOLTAGE
PROG.
FIGURE 3. BLOCK DIAGRAM
Pin Configuration
ISL91127
(20 BALL WLCSP, 0.4mm PITCH)
TOP VIEW, BUMPS DOWN
1
A
PVIN
2
PVIN
3
PVIN
VIN
LX1
LX1
LX1
EN
C
PGND
PGND
MODE
SGND
E
LX2
VOUT
FN8418 Rev 5.01
Aug 26, 2022
LX2
VOUT
LX2
VOUT
PIN #
PIN NAMES
A1, A2, A3
PVIN
Power input. Range: 1.8V to 5.5V. Connect
2x10μF capacitors to PGND.
B1, B2, B3
LX1
Inductor connection, input side
C1, C2
PGND
D1, D2, D3
LX2
E1, E2,
E3
VOUT
Buck-boost regulator output. Connect
2x22μF capacitors to PGND.
C3
MODE
Logic input, HIGH for auto PFM mode. LOW
for forced PWM operation.
A4
VIN
Supply input. Range: 1.8V to 5.5V.
B4
EN
Logic input, drive HIGH to enable device.
C4, D4
SGND
E4
FB
4
B
D
Pin Descriptions
SGND
FB
DESCRIPTION
Power ground for high switching current
Inductor connection, output side
Analog ground pin
Voltage feedback pin
Page 2 of 12
ISL91127
Ordering Information
PART NUMBER
(Notes 2, 3)
ISL91127IINZ-T
PART
MARKING
OUTPUT VOLTAGE
PACKAGE
(V)
(RoHS COMPLIANT)
GAXU
3.3
20 Ball WLCSP
PKG.
DWG. #
CARRIER TYPE
(Note 1)
TEMP. RANGE
W4x5.20M
Reel, 3k
-40 to +85°C
ISL91127IINZ-T7A
ISL91127II2AZ-T
Reel, 250
GAXV
3.5
Reel, 3k
ISL91127II2AZ-T7A
ISL91127IIAZ-T
Reel, 250
GAXT
ADJ
Reel, 3k
ISL91127IIAZ-T7A
Reel, 250
ISL91127IIN-EVZ
Evaluation Board for ISL91127IINZ
ISL91127II2A-EVZ
Evaluation Board for ISL91127II2AZ
ISL91127IIA-EVZ
Evaluation Board for ISL91127IIAZ
NOTES:
1. Refer to TB347 for details about reel specifications.
2. These Pb-free WLCSP packaged products employ special Pb-free material sets; molding compounds/die attach materials and SnAgCu - e1 solder ball
terminals, which are RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Pb-free WLCSP packaged products are MSL
classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), see the ISL91127 product information page. For more information about MSL, see TB363.
TABLE 1. KEY DIFFERENCES BETWEEN FAMILY OF PARTS
BUCK-BOOST
REGULATION
BYPASS
DYNAMIC VOLTAGE
SCALING
I2C
PACKAGE
ISL91127
Yes
No
No
No
WLCSP
ISL91127IR
Yes
No
No
No
QFN
ISL91128
Yes
Yes
Yes
Yes
WLCSP
PART NUMBER
NOTE: For the full family of ISL911xx buck-boost regulators, please visit our website.
FN8418 Rev 5.01
Aug 26, 2022
Page 3 of 12
ISL91127
Absolute Maximum Ratings
Thermal Information
PVIN, VIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.5V
LX1, LX2. . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.5VDC, -2V to 7V for 10ns
FB (Adjustable Version) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 2.7V
FB (Fixed VOUT Versions) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.5V
GND, PGND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 0.3V
All Other Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.5V
ESD Rating
Human Body Model (Tested per JS-001-2010). . . . . . . . . . . . . . . . .2.5kV
Machine Model (Tested per JESD22-A115C) . . . . . . . . . . . . . . . . . 250V
Charged Device Model (Tested per JS-002-2014) . . . . . . . . . . . . . . . 1kV
Latch-Up (Tested per JESD-78D; Class 2, Level A) . . . . . . . . . . . . . . 100mA
Thermal Resistance (Typical)
JA (°C/W) JB (°C/W)
20 Ball WLCSP Package (Notes 4, 5) . . . .
72
16
Maximum Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . .+125°C
Storage Temperature Range. . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see TB493
Recommended Operating Conditions
Ambient Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . -40°C to +85°C
Supply Voltage Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8V to 5.5V
Maximum Load Current
VIN = 2.5V VOUT = 3.3V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1ADC
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:
4. JA is measured in free air with the component mounted on a high-effective thermal conductivity test board with “direct attach” features. See TB379.
5. For JB, the board temp is taken on the board near the edge of the package, on a trace at the middle of one side. See TB379.
Analog Specifications VIN = VPVIN = VEN = 3.6V, VOUT = 3.3V, L1 = 1µH, C1 = 2x10µF, C2 = 2x22µF, TA = +25°C. Boldface limits apply
across the operating temperature range, -40°C to +85°C and input voltage range (1.8V to 5.5V) unless specified otherwise.
PARAMETER
SYMBOL
TEST CONDITIONS
MIN
TYP
MAX
(Note 6) (Note 7) (Note 6)
UNIT
POWER SUPPLY
Input Voltage Range
VIN Undervoltage Lockout Threshold
1.8
5.5
V
1.795
V
30
55
µA
0.05
1.00
µA
1.00
5.20
V
VIN = 3.7V, VOUT = 3.3V, IOUT = 0mA, PWM mode
-2
+2
%
VIN = 3.7V, VOUT = 3.3V, IOUT = 1mA, PFM mode
-3
+4
%
VIN
VUVLO
Rising
Falling
VIN Supply Current
IVIN
PFM mode, 1.8V ≤ VIN ≤ 5V, no external load on
VOUT (Note 8)
VIN Supply Current, Shutdown
ISD
EN = GND, VIN = 3.6V
1.725
1.550
1.650
V
OUTPUT VOLTAGE REGULATION
Output Voltage Range
VOUT
Output Voltage Accuracy
ISL91127IIAZ, IOUT = 100mA, VIN = 3.6V
FB Pin Voltage Regulation
VFB
For adjustable output version, VIN = 3.6V
FB Pin Bias Current
IFB
For adjustable output version
0.783
0.800
0.813
V
20
nA
Line Regulation, PWM Mode
VOUT/
VIN
IOUT = 500mA, VIN steps from 2.8V to 5.5V
2.2
mV/V
Line Regulation, PFM Mode
VOUT/
VI
IOUT = 100mA, VIN steps from 2.8V to 5.5V
2.7
mV/V
Load Regulation
VOUT/
IOUT
VIN = 3.7V, IOUT steps from 0A to 1A
0.021
mV/mA
Output Voltage Clamp
VCLAMP
Rising
5.25
Output Voltage Clamp Hysteresis
5.95
400
V
mV
DC/DC SWITCHING SPECIFICATIONS
Oscillator Frequency
2.10
fSW
2.50
2.90
MHz
80
ns
Minimum On-Time
tON(MIN)
LX1 Pin Leakage Current
IPFETLEAK
VIN = 3.6V
-1
1
µA
LX2 Pin Leakage Current
INFETLEAK
VIN = 3.6V
-1
1
µA
FN8418 Rev 5.01
Aug 26, 2022
Page 4 of 12
ISL91127
Analog Specifications VIN = VPVIN = VEN = 3.6V, VOUT = 3.3V, L1 = 1µH, C1 = 2x10µF, C2 = 2x22µF, TA = +25°C. Boldface limits apply
across the operating temperature range, -40°C to +85°C and input voltage range (1.8V to 5.5V) unless specified otherwise. (Continued)
PARAMETER
MIN
TYP
MAX
(Note 6) (Note 7) (Note 6)
UNIT
Time from when EN signal asserts to when output
voltage ramp starts.
1
ms
Time from when output voltage ramp starts to when
output voltage reaches 95% of its nominal value
with device operating in Buck mode.
VIN = 4V, VOUT = 3.3V, IO = 200mA
2
ms
Time from when output voltage ramp starts to when
output voltage reaches 95% of its nominal value
with device operating in Boost mode.
VIN = 2V, VOUT = 3.3V, IO = 200mA
2
ms
120
Ω
SYMBOL
TEST CONDITIONS
tSS
SOFT-START AND SOFT DISCHARGE
Soft-Start Time
VOUT Soft Discharge ON-Resistance
rDISCHG
EN < VIL
POWER MOSFET
P-Channel MOSFET ON-Resistance
rDS(ON)_P VIN = 3.6V, IO = 200mA
28
mΩ
N-Channel MOSFET ON-Resistance
rDS(ON)_N VIN = 3.6V, IO = 200mA
26
mΩ
P-Channel MOSFET Peak Current Limit
IPK_LMT
VIN = 3.6V
3.8
4.3
5.0
A
PFM/PWM TRANSITION
Load Current Threshold, PFM to PWM
VIN = 3.6V, VOUT = 3.3V
360
mA
Load Current Threshold, PWM to PFM
VIN = 3.6V, VOUT = 3.3V
160
mA
Thermal Shutdown
150
°C
Thermal Shutdown Hysteresis
30
°C
LOGIC INPUTS
ILEAK
VIN = 3.6V
Input HIGH Voltage
VIH
VIN = 3.6V
Input LOW Voltage
VIL
VIN = 3.6V
Input Leakage
0.05
1
µA
0.4
V
1.4
V
NOTES:
6. Parameters with MIN and/or MAX limits are 100% tested at +25°C, unless otherwise specified. Temperature limits established by characterization
and are not production tested.
7. Typical values are for TA = +25°C and VIN = 3.6V.
8. Quiescent current measurements are taken when the output is not switching.
FN8418 Rev 5.01
Aug 26, 2022
Page 5 of 12
ISL91127
Typical Performance Curves
Unless otherwise noted, operating conditions are: TA = +25°C, VIN = EN = 3.6V, L1 = 1µH,
C1 = 2x10µF, C2 = 2x22µF, VOUT = 3.3V, IOUT = 0A to 3A.
100
3.294
LOAD = 100mA
98
3.29
OUTPUT VOLTAGE (V)
EFFICIENCY (%)
96
94
92
90
LOAD = 10mA
88
86
84
LOAD = 1000mA
3.288
3.286
3.28
3.278
VIN = 3.6V
3.276
3.274
3.272
3.27
3
VIN = 3.3V
3.282
80
2.5
VIN = 3V
3.284
82
2
VIN = 4V
3.292
LOAD = 500mA
3.5
4
4.5
VI N = 2.5V
1
5
10
100
100 0
LOAD CURRENT (mA)
VIN (V )
FIGURE 5. OUTPUT VOLTAGE vs LOAD CURRENT
FIGURE 4. EFFICIENCY vs INPUT VOLTAGE
80
TA = +25oC
2.45
TA = +85oC
SWITCHING FREQUENCY (MHz)
QUIESCENT CURRENT (µA)
70
60
50
40
30
TA = -40oC
20
10
2.4
2.35
2.3
2.25
2.2
2.15
0
1.5
2
2.5
3
3.5
4
VIN (V)
4.5
5
5.5
6
FIGURE 6. QUIESCENT CURRENT vs INPUT VOLTAGE (VOUT = 3.3V,
MODE = HIGH)
1 .5
2.5
3.5
VIN (V)
4.5
5.5
FIGURE 7. SWITCHING FREQUENCY vs INPUT VOLTAGE
LX1 (2V/DIV)
LX2 (2V/DIV)
LX2 (2V/DIV)
LX1 (2V/DIV)
VOUT (AC, 50mV/DIV)
IL (500mA/DIV)
400ns/DIV
FIGURE 8. STEADY-STATE OPERATION IN PFM (VIN = 4V,
VOUT = 3.3V, NO LOAD)
FN8418 Rev 5.01
Aug 26, 2022
VOUT (AC, 10mV/DIV)
IL (200mA/DIV)
400ns/DIV
FIGURE 9. STEADY-STATE OPERATION IN PWM (VIN = 3.3V,
VOUT = 3.3V, NO LOAD)
Page 6 of 12
ISL91127
Typical Performance Curves
Unless otherwise noted, operating conditions are: TA = +25°C, VIN = EN = 3.6V, L1 = 1µH,
C1 = 2x10µF, C2 = 2x22µF, VOUT = 3.3V, IOUT = 0A to 3A. (Continued)
VOUT (1V/DIV)
VOUT (1V/DIV)
EN (2V/DIV)
EN (2V/DIV)
IL (500mA/DIV)
IL (500mA/DIV)
400µs/DIV
FIGURE 10. SOFT-START (VIN = 3.6V, VOUT = 3.3V, NO LOAD)
400µs/DIV
FIGURE 11. SOFT-START (VIN = 3.6V, VOUT = 3.3V, 1A LOAD)
IL (1A/DIV)
LX1 (2V/DIV)
VOUT (AC, 100mV/DIV)
LX2 (2V/DIV)
IL (1A/DIV)
VOUT (AC, 100mV/DIV)
100µs/DIV
400ns/DIV
FIGURE 12. STEADY-STATE OPERATION (VIN = 2.5V, VOUT = 3.3V,
2A LOAD)
FIGURE 13. 0A TO 2A LOAD TRANSIENT (VIN = 3.6V, VOUT = 3.3V)
VOUT (AC, 100mV/DIV)
VOUT (AC, 100mV/DIV)
IL (500mA/DIV)
IL (500mA/DIV)
100µs/DIV
100µs/DIV
FIGURE 14. 0.5A TO 1.5A LOAD TRANSIENT (VIN = 3.6V, VOUT = 3.3V)
FIGURE 15. 0A TO 1A LOAD TRANSIENT (VIN = 3.6V, VOUT = 3.3V)
FN8418 Rev 5.01
Aug 26, 2022
Page 7 of 12
ISL91127
Typical Performance Curves
Unless otherwise noted, operating conditions are: TA = +25°C, VIN = EN = 3.6V, L1 = 1µH,
C1 = 2x10µF, C2 = 2x22µF, VOUT = 3.3V, IOUT = 0A to 3A. (Continued)
VIN (1V/DIV)
LX1 (2V/DIV)
LX2 (2V/DIV)
VOUT (2V/DIV)
VOUT (AC, 100mV/DIV)
IL (2A/DIV)
100µs/DIV
20ms/DIV
FIGURE 17. 4V TO 3.2V LINE TRANSIENT (VOUT = 3.3V, LOAD = 1A)
FIGURE 16. OUTPUT SHORT-CIRCUIT BEHAVIOR (VIN = 3.6V,
VOUT = 3.3V)
MAXIMUM OUTPUT CURRENT (A)
4.5
4.0
3.5
3.0
2.5
2.0
1.5
2.5
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
FIGURE 18. OUTPUT CURRENT CAPABILITY: VOUT = 3.3V, TA = +25°C
Functional Description
Enable Input
Functional Overview
Enable the device by asserting the EN pin HIGH. Driving EN LOW
invokes a power-down mode, in which most internal device
functions are disabled.
The ISL91127 implements a complete buck-boost switching
regulator with PWM controller, internal switches, references,
protection circuitry, and control inputs. Refer to the “Block
Diagram” on page 2
The PWM controller automatically switches between Buck and
Boost modes as necessary to maintain a steady output voltage
with changing input voltages and dynamic external loads.
Internal Supply and References
Referring to the “Block Diagram”, the ISL91127 provides three
PVIN power input pins. The PVIN pins supply input power to the
DC/DC converter. An additional VIN pin provides an operating
voltage source required for stable VREF generation. Separate
ground pins (PGND and SGND) are provided to avoid problems
caused by ground shift due to the high switching currents.
FN8418 Rev 5.01
Aug 26, 2022
Soft Discharge
When the device is disabled by driving EN LOW, an internal resistor
between VOUT and GND is activated to slowly discharge the output
capacitor. This internal resistor has a typical 120Ω resistance.
POR Sequence and Soft-Start
Asserting the EN pin HIGH allows the device to power up. The
following events occur during the start-up sequence: The internal
voltage reference powers up and stabilizes. The device then
starts operating. There is a typical 1ms delay between assertion
of the EN pin and the start of the switching regulator soft-start
ramp.
The soft-start feature minimizes output voltage overshoot and
input inrush currents. During soft-start, the reference voltage is
ramped to provide a ramping VOUT voltage. While the output
voltage is lower than approximately 20% of the target output
Page 8 of 12
ISL91127
voltage, switching frequency is reduced to a fraction of the
normal switching frequency to aid in producing low duty cycles
necessary to avoid input inrush current spikes. When the output
voltage exceeds 20% of the target voltage, the switching
frequency is increased to its nominal value.
When the target output voltage is higher than the input voltage,
the device transitions from Buck mode to Boost mode during the
soft-start sequence. At the time of this transition, the ramp rate
of the reference voltage is decreased, such that the output
voltage slew rate is decreased. This provides a slower output
voltage slew rate.
The VOUT ramp time is not constant for all operating conditions.
Soft-start into Boost mode takes longer than soft-start into Buck
mode. The total soft-start time into Buck operating mode is
typically 2ms, whereas the typical soft-start time into Boost
operating mode is typically 3ms. Increasing the load current
increases these typical soft-start times.
Short-Circuit Protection
The ISL91127 provides short-circuit protection by monitoring the
feedback voltage. When feedback voltage is sensed to be lower
than a certain threshold, the PWM oscillator frequency is
reduced in order to protect the device from damage. The
P-channel MOSFET peak current limit remains active during
this state.
Thermal Shutdown
A built-in thermal protection feature protects the ISL91127 if the
die temperature reaches +155°C (typical). At this die
temperature, the regulator is completely shut down. The die
temperature continues to be monitored in this thermal shutdown
mode. When the die temperature falls to +125°C (typical), the
device will resume normal operation. When exiting thermal
shutdown, the ISL91127 will execute its soft-start sequence.
Buck-Boost Conversion Topology
The ISL91127 operates in either Buck or Boost mode. When
operating in conditions where PVIN is close to VOUT, the
ISL91127 alternates between Buck and Boost modes as
necessary to provide a regulated output voltage.
L1
LX1
SWITCH A
PWM Operation
During PWM operation in Buck mode, Switch D is continuously
closed and Switch C is continuously open. Switches A and B
operate as a synchronous buck converter when in this mode.
During PWM operation in Boost mode, Switch A remains closed
and Switch B remains open. Switches C and D operate as a
synchronous boost converter when in this mode.
PFM Operation
During PFM operation in Buck mode, Switch D is continuously
closed and Switch C is continuously open. Switches A and B
operate in discontinuous mode during PFM operation. During
PFM operation in Boost mode, the ISL91127 closes Switch A and
Switch C to ramp up the current in the inductor. When the
inductor current reaches a certain threshold, the device turns off
Switches A and C, then turns on Switches B and D. With Switches
B and D closed, output voltage increases as the inductor current
ramps down.
In most operating conditions, there will be multiple PFM pulses
to charge up the output capacitor. These pulses continue until
VOUT has achieved the upper threshold of the PFM hysteretic
controller. Switching then stops, and remains stopped until VOUT
decays to the lower threshold of the hysteretic PFM controller.
Operation with VIN Close to VOUT
When the output voltage is close to the input voltage, the
ISL91127 rapidly and smoothly switches from Boost to Buck
mode as needed to maintain the regulated output voltage. This
behavior provides excellent efficiency and very low output
voltage ripple.
Output Voltage Programming
The ISL91127 is available in fixed and adjustable output voltage
versions. To use the fixed output version, the VOUT pin must be
connected directly to FB.
In the adjustable output voltage version (ISL91127IIAZ), an
external resistor divider is required to program the output
voltage. The FB pin has very low input leakage current, so it is
possible to use large value resistors (for example, R1 = 1MΩ and
R2 = 324kΩ for VOUT = 3.3V) in the resistor divider connected to
the FB input.
LX2
SWITCH D
PVIN
VOUT
SWITCH B
SWITCH C
FIGURE 19. BUCK-BOOST TOPOLOGY
Figure 19 shows a simplified diagram of the internal switches
and external inductor.
FN8418 Rev 5.01
Aug 26, 2022
Page 9 of 12
ISL91127
Applications Information
Feed-Forward Capacitor Selection
A small capacitor (C3 in Figure 19) in parallel with resistor R1 is
required to provide the specified load and line regulation. The
suggested value of this capacitor is 56pF for R1 = 1MΩ. An NPO
type capacitor is recommended.
Component Selection
The fixed-output version of the ISL91127 requires only three
external power components to implement the buck-boost
converter: an inductor, an input capacitor, and an output
capacitor.
Inductor Selection
The adjustable output version of the ISL91127 requires three
additional components to program the output voltage, as shown
in Figure 19. Two external resistors program the output voltage
and a small capacitor is added to improve stability and response.
.
ISL91127IIAZ
VIN = 1.8V TO 5.5V
C1
10µF
PVIN
LX1
L1
1µH
LX2
VIN
VOUT = 1V TO
VOUT
EN
R1
PGND
SGND
MODE
C3
C2
2x22µF
FB
R2
Use an inductor with high frequency core material (for example,
ferrite core) to minimize core losses and provide good efficiency.
The inductor must be able to handle the peak switching currents
without saturating.
A 1µH inductor with ≥4A saturation current rating is
recommended. Select an inductor with low DCR to provide good
efficiency. In applications where radiated noise must be
minimized, a toroidal or shielded inductor can be used (refer to
Table 3).
PVIN and VOUT Capacitor Selection
The input and output capacitors should be ceramic X5R type with
low ESL and ESR. The recommended input capacitor value is
10µF. The recommended VOUT capacitor value is 2x22µF.
TABLE 2. CAPACITOR VENDOR INFORMATION
FIGURE 20. ADJUSTABLE OUTPUT APPLICATION
MANUFACTURER
Output Voltage Programming, Adjustable
Version
Select the external resistor values to set and control the output
voltage of the ISL91127IIAZ (adjustable output version).
DESCRIPTION
Murata
GRM188R61A226ME15D 22µF, 0603, 10V, X5R
TDK
C1608X5R1A226M080AC 22µF, 0603, 10V, X5R
Recommended PCB Layout
Equation 1 can be used to derive the R1 and R2 resistor values:
R
V OUT = 0.8V 1 + ------1-
R
2
PN
(EQ. 1)
When designing a PCB, include a GND guard band around the
feedback resistor network to reduce noise and improve accuracy
and stability. Position resistors R1 and R2 close to the FB pin.
Correct PCB layout is critical for proper operation of the
ISL91127. Place the input and output capacitors as close to the
IC as possible. The ground connections of the input and output
capacitors should be kept as short as possible and should be on
the component layer to avoid problems that are caused by high
switching currents flowing through PCB vias.
TABLE 3. INDUCTOR VENDOR INFORMATION
MANUFACTURER
Toko
Coilcraft
MANUFACTURER
PART NUMBER
DESCRIPTION
DIMENSION
(mm)
WEBSITE
1277AS-H-1R0M
1µH, 20%, DCR = 34mΩtypicalISAT = 4.6A (typical)
3.2x2.5x1.2 www.toko.com
FDSD0312-H-1R0M
1µH, 20%, DCR = 43mΩtypicalISAT = 4.5A (typical)
3.2x3.0x1.2
XFL4020-102ME
1µH, 20%, DCR = 11mΩtypicalISAT = 5.1A (typical)
4.0x4.0x2.1 www.coilcraft.com
FN8418 Rev 5.01
Aug 26, 2022
Page 10 of 12
ISL91127
Revision History
The revision history provided is for informational purposes only and is believed to be accurate, however, not warranted. Please visit to web to make sure
you have the latest revision.
DATE
REVISION
Aug 26, 2022
5.01
Updated Ordering Information table formatting.
Updated first sentence in the Output Voltage Programming, Adjustable Version section.
Jan 28, 2022
5.00
Updated Figure 3: Removed the resistive connection between EN and SGND.
Removed Related Literature.
May 24, 2018
4.00
Removed About Intersil section.
Updated Disclaimer and moved to page 13.
Jan 5, 2017
3.00
Updated Related Literature section on page 1.
Updated Table 1 on page 3.
- changed “VSEL” column to “Dynamic Voltage Scaling” and made ISL91128 parameter “Yes”.
- removed “and DVS” from I2C column.
Aug 9, 2016
2.00
Removed burst current features bullet on page 1.
Updated Table 1 on page 3.
Removed “VIN = 3.0V VOUT = 3.3V, tON = 600µs, t = 4.6ms...3A” from the “Recommended Operating
Conditions” on page 4.
Jul 15, 2016
1.00
Updated 2 feature bullets to clarify statement.
Updated Table 1 on page 3.
Updated test conditions for VIN supply current page 4 from “PFM mode, no external load on VOUT” to “PFM
mode, 1.8V ≤ VIN ≤ 5V, no external load on”.
Updated “P-Channel MOSFET ON-Resistance” typical from 35 to 28 and “N-Channel MOSFET ON-Resistance”
typical from 24 to 26 typical.
Added Figure 18, “OUTPUT CURRENT CAPABILITY” to typical Performance Curves” on page 8.
Apr 5, 2016
0.00
Initial Release
FN8418 Rev 5.01
Aug 26, 2022
CHANGE
Page 11 of 12
ISL91127
Package Outline Drawing
For the most recent package outline drawing, see W4x5.20M.
W4x5.20M
20 BALL WAFER LEVEL CHIP SCALE PACKAGE (WLCSP 0.4mm PITCH)
Rev 0, 01/15
X
Y
0.400
1.74 ±0.030
20x 0.265 ±0.035
E
D
C
2.15 ±0.030
B
A
(4X)
0.10
PIN 1
(A1 CORNER)
TOP VIEW
0.275
1
2
3
4
0.200
0.270
BOTTOM VIEW
0.240
Z
PACKAGE
OUTLINE
0.05 Z
SEATING PLANE
3
0.400
0.290
2
0.265 ±0.035 x20
0.10
0.05
ZXY
Z
4
0.200 ±0.030
6 NSMD
RECOMMENDED LAND PATTERN
0.500 ±0.050
SIDE VIEW
NOTES:
9. Dimensions and tolerance per ASMEY 14.5 - 1994.
10. Dimension is measured at the maximum bump diameter parallel to primary datum Z.
11. Primary datum Z and seating plane are defined by the spherical crowns of the bump.
12. Bump position designation per JESD 95-1, SPP-010.
13. All dimensions are in millimeters.
14. NSMD refers to non-solder mask defined pad design per Intersil Techbrief TB451.
FN8418 Rev 5.01
Aug 26, 2022
Page 12 of 12
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