LTM4712
APPLICATIONS INFORMATION
Table 2. Switching Frequency vs RT Value
The typical LTM4712 application circuit is shown on the
front page. External component selection is primarily
determined by the input voltage, the output voltage, and
the maximum load current.
FREQUENCY
(kHz)
R VALUE
T
(kΩ)
100
200
300
400
500
600
58
80
120
140
170
200
Output Voltage Programming
The PWM controller has an internal 1V reference voltage.
A 100k internal feedback resistor connects V
and FB
OUT
pins together. Adding a resistor R from the FB pin to
FB
GND programs the output voltage (see Equation 1).
A phase-locked loop (PLL) is integrated to synchronize the
internal oscillator to an external clock source driving the
SYNC pin. The PLL is capable of locking to any frequency
within the range of 100kHz to 600kHz. The frequency set-
ting resistor at FREQ pin should always be present to set
the controller’s initial switching frequency before locking
to the external clock or in any cases the external clock is
missing during the operation. The CLKOUT pin is a clock
signal output with the same frequency as the internal
oscillator with phase shift programmed by the PHMODE
pin. It can be used in multi-IC parallel applications by
passing the clock signal of the first IC to the SYNC pin of
the second IC for frequency synchronization. The phase
shift can be programmed based on Table 3.
100
VOUT
RFB (kΩ) =
(1)
1
Table 1. VFB Resistor Table vs Various Output Voltages
V
(V)
3.3
5
8
12
16
20
24
28
OUT
R
(k)
43.5
25
14.3 9.09 6.67 5.23 4.35
3.74
FB
For parallel operation of N-channels LTM4712,
Equation 2 can be used to solve for R .
FB
100
N • VOUT
RFB (kΩ) =
(2)
1
Operating Frequency Selection and Phase-Locked
Loop (FREQ, SYNC, PHMODE and CLKOUT Pins)
Table 3. PHMODE Setting vs CLKOUT Phase Shift
CLKOUT PHASE SHIFT REFERS TO
PHMODE PIN
SGND
THE INTERNAL OSCILLATOR
The switching frequency of the LTM4712 can be selected
using the FREQ pin. If the SYNC pin is not being driven
by an external clock source, the FREQ pin is used to pro-
gram the controller’s operating frequency from 100kHz to
600kHz. Switching frequency is determined by the voltage
on the FREQ pin. Since there is a precision 10μA current
flowing out of the FREQ pin, program the controller’s
switching frequency with a single resistor to SGND (e.g.,
the FREQ pin voltage is 1.58V with 158k resistor from the
180°
120°
90°
FLOAT
INTV
CC
Input Decoupling Capacitors
In boost mode, since the input current is continuous,
only minimum input capacitors are required. However,
the input current is discontinuous in buck mode. So the
FREQ pin to SGND). Table 2 provides a list of R resistor
values and their resultant frequencies.
T
selection of input capacitor C is driven by the need of
IN
filtering the input square wave current.
Rev. 0
10
For more information www.analog.com
5秒后页面跳转
STM32H743技术深度剖析与应用案例探索
LM321中文资料解析：引脚功能介绍、技术特点、技术特性分析
74HC14芯片资料介绍：性能特性分析、引脚介绍
LM1875芯片手册：功放参数分析、引脚说明、电路设计要点
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
数据手册
如果您发现信息不准确，
