LTC3576EUFE#PBF Linear Technology, LTC3576EUFE#PBF Datasheet - Page 33

• Manufacturer Part Number: LTC3576EUFE#PBF
• Description: IC POWER MANAGER W/USB OTG 38QFN
• Manufacturer: Linear Technology

Specifications of LTC3576EUFE#PBF

• Applications: Handheld/Mobile Devices
• Voltage - Supply: 4.35 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 38-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Supply: -

Bidirectional PowerPath Switching Regulator
CLPROG Resistor and Capacitor Selection
As described in the Bidirectional Switching Regula-
tor—Step-Down Mode section, the resistor on the
CLPROG pin determines the average V
limit when the switching regulator is set to either the 1×
mode (USB 100mA), the 5× mode (USB 500mA) or the
10× mode. The V
two components, the current that is used to drive V
and the quiescent current of the switching regulator. To
ensure that the USB specifi cation is strictly met, both
components of the input current should be considered.
The Electrical Characteristics table gives the typical values
for quiescent currents in all settings as well as current limit
programming accuracy. To get as close to the 500mA or
100mA specifi cations as possible, a precision resistor
should be used. Recall that:
An averaging capacitor is required in parallel with the
resistor so that the switching regulator can determine the
average input current. This capacitor also provides the
dominant pole for the feedback loop when current limit
is reached. To ensure stability, the capacitor on CLPROG
should be 0.1μF or larger.
Bidirectional PowerPath Switching Regulator
Inductor Selection
Because the input voltage range and output voltage range
of the PowerPath switching regulator are both fairly nar-
row, the LTC3576/LTC3576-1 were designed for a specifi c
inductance value of 3.3μH. Some inductors which may be
suitable for this application are listed in Table 7.
Table 7. Recommended PowerPath Inductors for the LTC3576
INDUCTOR
TYPE
LPS4018
D53LC
DB318C
WE-TPC
Type M1
CDRH6D12
CDRH6D38
APPLICATIONS INFORMATION
I
VBUS
= I
(μH)
VBUSQ
3.3
3.3
3.3
3.3
3.3
3.3
L
MAX
2.26
1.55
1.95 0.065 4.8 × 4.8 × 1.8 Wurth Electronik
I
(A)
2.2
2.2
3.5
BUS
+ V
DC
CLPROG
input current will be comprised of
0.034
0.070
0.063
0.020
MAX
DCR
0.08 3.9 × 3.9 × 1.7 Coilcraft
(Ω)
3.8 × 3.8 × 1.8
6.7 × 6.7 × 1.5
/R
SIZE IN mm
(L × W × H) MANUFACTURER
5 × 5 × 3
7 × 7 × 4
CLPPROG
BUS
• (h
www.coilcraft.com
Toko
www.toko.com
www.we-online.com
Sumida
www.sumida.com
CLPROG
input current
+1).
OUT
Bidirectional PowerPath Switching Regulator V
and V
The type and value of capacitors used with the LTC3576/
LTC3576-1 determine several important parameters such
as regulator control-loop stability and input voltage ripple.
Because the LTC3576/LTC3576-1 use a bidirectional
switching regulator between V
current waveform contains high frequency components.
It is strongly recommended that a low equivalent series
resistance (ESR) multilayer ceramic capacitor (MLCC) be
used to bypass V
are not recommended because of their high ESR. The value
of the capacitor on V
input ripple for a given load current. Increasing the size
of this capacitor will reduce the input ripple.
The inrush current limit specifi cation for USB devices is
calculated in terms of the total number of Coulombs needed
to charge the V
inrush charge for USB on-the-go devices is 33μC. This
places a limit of 6.5μF of capacitance on V
a linear capacitor. However, most ceramic capacitors have
a capacitance that varies with bias voltage. The average
capacitance needs to be less than 6.5μF over a 0V to 5V bias
voltage range to meet the inrush current limit specifi cation.
A 10μF capacitor in a 0805 package, such as the Murata
GRM21BR71A106KE51L would be a suitable V
capacitor. If more capacitance is required for better noise
performance and stability it should be connected directly to
the V
This extra capacitance will be soft-connected over several
milliseconds to limit inrush current and avoid excessive
transient voltage drops on V
To prevent large V
conditions, it is also recommended that an MLCC be used
to bypass V
pensation of the switching regulator. At least 10μF with
low ESR are required on V
improve load transient performance and stability.
MLCCs typically have exceptional ESR performance.
MLCCs combined with a tight board layout and an unbroken
ground plane will yield very good performance and low
EMI emissions.
BUS
OUT
pin when using the overvoltage protection circuit.
Bypass Capacitor Selection
OUT
BUS
. The output capacitor is used in the com-
LTC3576/LTC3576-1
BUS
OUT
bypass capacitor to 5V. The maximum
. Tantalum and aluminum capacitors
BUS
voltage steps during transient load
directly controls the amount of
OUT
BUS
. Additional capacitance will
BUS
.
and V
OUT
BUS
BUS
, the V
assuming
33
BUS
bypass
3576fb
BUS