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PDF ( 数据手册 , 数据表 ) ML1565

零件编号 ML1565
描述 Step-Up-Down DC-DC Converts
制造商 Minilogic Device
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ML1565 数据手册, 描述, 功能
ML1565
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Step-Up-Down DC-DC Converts
Digital Still camera Power Supply
High-Efficiency, 5-channel
ML1565
General Description
The ML1565 provides a complete power-supply solution
for digital still and video cameras through the integration
of ultra-high-efficiency step-up/step-down DC-to-DC con-
verters along with three auxiliary step-up controllers. The
ML1565 is targeted for applications that use either 2 or 3
alkaline or NiMH batteries as well as those using a single
lithium-ion (Li+) battery.
The step-up DC-to-DC converter accepts inputs from 0.7V
to 5.5V and regulates a resistor-adjustable output from
2.7V to 5.5V. It uses internal MOSFETs to achieve
95% efficiency. Adjustable operating frequency facilitates
design for optimum size, cost, and efficiency.
The step-down DC-to-DC converter can produce output
voltages as low as 1.25V and also utilizes internal
MOSFETs to achieve 95% efficiency. An internal softstart
ramp minimizes surge current form the battery. The
converter can operate from the step-up output providing
buck-boost capability with up to 90% compound efficiency,
or it can run directly from the battery if buck-boost
operation is not needed. The ML1565 features auxiliary
step-up controllers that power CCD, LCD, motor actuator,
and backlight circuits. The ML1565 is available in a
space-saving QFN-32 thin package.
Pin Configuration
Features
Step-up DC-to-DC Converter:
95% Efficient
3.3V (Fixed) or 2.7V to 5.5V (Adjustable) Output
Voltage
Step-Down DC-to-DC Converter:
Operate form Battery for 95% Efficient Buck
Combine with Step-Up for 90% Efficient Buck-Boost
Adjustable Output Down to 1.25V
Three Auxiliary PWM Controllers
Up to 1MHz Operating Frequency
1µA Shutdown Mode
Internal Soft-Start control
Overload Protection
Compact 32-Pin, 5mmx5mm Thin QFN Package
Ordering Information
Item
ML1565QFNG
Package Mark
Shipping
QFN-32 ML1565 160pcs/ Tray
Applications
Digital Still Cameras
Digital video Cameras
PDAs
Typical operating Circuit
ML1565
ML1565
--
P1/21
Rev. C, Sep 2005







ML1565 pdf, 数据表
ML1565
Pin Description
Pin16 FBSELSU
Pin17 FBSELSD
Pin18 FBSEL1
Pin19 OSC
Pin20 PGNDB
Pin21 LXSU
Pin22 OUTSUA
Pin23 SDOK
Pin24 COMP3
Pin25 FB3
Pin26 OUTSUB
Pin27 DL3
Pin28 DL2
Pin29 DL1
Pin30 GND
Pin31 COMP2
Pin32 FB2
Exposed EP
Pad
Step-Up Feedback Select Pin. With FBSELSD = GND, OUTSU regulates to 3.35V. With FBSELSD =
OUTSU, FBSU regulates to a 1.25V threshold for use with external feedback resistors. This pin is high
impedance in shutdown.
Step-Down Feedback Select Pin. With FBSELSD = GND, FBSD regulates to 1.5V. With FBSELSD =
OUTSU, FBSD regulates to a 1.25V for use with external feedback resistors. This pin is high
impedance in shutdown.
Auxiliary Controller 1 Feedback Select Pin. With FBSEL1 = GND and FB1 regulates to 5V. With
FBSEL1=OUTSU, FB1 regulates to 1.25V for use with external feedback resistors. This pin is high
impedance in shutdown.
Oscillator Control. Connect a timing capacitor from OSC to GND and a timing resistor from OSC to
OUTSU to set the oscillator frequency between 100kHz and 1MHz. This pin is high impedance in
shutdown.
Power Ground. Connect PGNDA and PGNDB together and to GND with short trace as close to the IC
as possible.
Step-Up Converter Power-Switching Node. Connect LXSU to the step-up converter inductor. LXSU is
high impedance in shutdown.
Step-Up Converter Output. OUTSUA is the power output of the step-up converter. Connect OUTSUA
to OUTSUB at the IC.
This open-drain output goes high impedance when the step-down has successfully completed
soft-start.
Auxiliary Controller 3 Compensation Node. Connect a series resistor-capacitor form COMP3 to GND
to compensate the control loop. COMP3 is actively driven to GND in shutdown and thermal limit.
Auxiliary Controller 3 Feedback Input. Connect a resistive voltage-divider from the output voltage to
FB3 to GND. The FB3 feedback threshold is 1.25V. This pin is high impedance in shutdown.
Step-Up Converter Output. OUTSUB powers the ML1565 and is the sense input when FBSELSU is
GND and the output is 3.3V. Connect OUTSUA to OUTSUB.
Auxiliary Controller 3 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL3. DL3
swings from GND to OUTSU and supplies up to 500mA. DL3 is driven to GND in shutdown and
thermal limit.
Auxiliary Controller 2 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL2. DL2
swings from GND to OUTSU and supplies up to 500mA. DL2 is driven to GND in shutdown and
thermal limit.
Auxiliary Controller 1 Gate-Drive Output. Connect the gate of an N-channel MOSFET to DL1. DL1
swings from GND to OUTSU and supplies up to 500mA. DL1 is driven to GND in shutdown and
thermal limit.
Quiet Ground. Connect GND to PGND as close to the IC as possible.
Auxiliary Controller 2 compensation Node. Connect a series resistor-capacitor from COMP2 to GND to
compensate the control loop. COMP2 is actively driven to GND in shutdown and thermal limit.
Auxiliary Controller 2 Feedback Input. Connect a resistive voltage-divider form the output voltage to
FB2 to GND to set the output voltage. The FB2 feedback threshold is 1.25V. This pin is high
impedance in shutdown.
Exposed Underside Metal Pad. This pad must be soldered to the PC board to achieve package
thermal and mechanical ratings. The exposed pad is electrically connected to GND.
P8/21
Rev. C, Sep 2005







ML1565 equivalent, schematic
ML1565
Design Procedure (4)
Step-Down Component Selection
Step-Down Inductor
The external components required for the step-down are
an inductor, input and output filter capacitors, and
compensation RC network. The ML1565 step-down
converter provides best efficiency with continuous inductor
current. A reasonable inductor value (LIDEAL) can be
derived from:
LIDEAL = 2(VIN) D (1-D) / (IOUT fOSC)
which sets the peak-to-peak inductor current at 1/2 the DC
inductor current. D is the duty cycle:
D = VOUT / VIN
Given LIDEAL, the peak-to-peak inductor current variation is
0.5 IOUT. The absolute peak inductor current is 1.25 IOUT.
Inductance values smaller than LIDEAL can be used to
reduce inductor size. However, if much smaller values are
used, inductor current rises and a large output
capacitance may be required to suppress output ripple.
Larger values than LIEDAL can be used to obtain higher
output current, but with typical larger inductor size.
Step-Down Compensation
The relevant characteristics for step-down compensation
are:
1) Transconductance (from FBSD to COMPSD), gmEA
(135µS)
2) Step-down slope compensation pole,
PSLOPE = VIN / (π L)
3) Current-sense amplifier transresistance,Rcs, (0.6V/A)
4) Feedback regulation voltage, VFB(1.25V)
5) Step-down output voltage, VSD, in V
6) Output load equivalent resistance,
RLOAD in = VOUTSD / ILOAD
The key steps for step-down compensation are:
1) Set the compensation RC zero to cancel the RLOAD
COUT pole.
2) Set the loop crossover below the lower of 1/5 the
slope compensation pole, or 1/5 the switching
frequency.
If we assume VIN = 3.35V, VOUT = 1.5V, and
IOUT = 350mA, then RLOAD = 4.3
If we select L = 4.7µH and fOSC = 440kHz,
PSLOPE = VIN / (πL) = 214kHz, so choose fc = 40kHz and
calculate Cc:
Cc = (VFB / VOUT)(RLOAD / RCS) (gm / 2π fc)
=(1.25/1.5)(4.3/0.6) x (135µS/(6.28 x 40kHz))
= 3.2nF
P16/21
Choose 3.3nF. Now select Rc such that transient droop
requirements are met. For example, if 4% transient droop
is allowed, the input to the error amplifier moves 0.04 x
1.25V, or 50mV. The error amp output drives 50mV x
135µS, or 6.75µA across Rc to provide transient gain.
Since the current-sense transresistance is 0.6V/A, the
value of Rc that allows the required load step swing:
RC=0.6 IIND(PK) / 6.75µA
In a step-down DC-to-DC converter, if LIDEAL is used, output
current relates to inductor current by:
IIND(OK) = 1.25 IOUT
Thus, for a 250mA output load step with VIN = 3.35V and
VOUT = 1.5V:
Rc = (1.25 x 0.6 x 0.25) / 6.75µA = 27.8k
Choose 27k. Note that the inductor does not limit the
response in this case since it can ramp at
(VIN-VOUT)/4.7µH, or (3.35 – 1.5)/4.7µH = 394mA/µs
The output filter capacitor is then chosen so that the
COUTRLOAD pole cancels the RcCc zero:
COUTRLOAD = RcCc
For example: COUT = 27kx 3.3nF / 4.3 = 20.7µF
Choose 22µF. If the output filter capacitor has significant
ESR, a zero occurs at:
ZESR = 1 / (2πCOUTRESR)
If ZESR > fc, it can be ignored, as is typically the case with
ceramic output capacitors. If ZESR is less than fc, it should
be cancelled with a pole set by capacitor Cp connected
from COMPAD to GND.
Cp = COUTRESR / Rc
If Cp is calculated to be < 10pF, it can be omitted.
Auxiliary Controller Component Selection
Diode
For most auxiliary applications, a Schottky diode rectifies
the output voltage. The Schottky diode’s low forward
voltage and fast recovery time provide the best
performance in most applications. Silicon signal diodes
(such as 1N4148) are sometimes adequate in low-current
(<10mA) high-voltage (>10V) output circuits where the
output voltage is large compared to the diode forward
voltage.
Rev. C, Sep 2005










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