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| 型号： | MAX16976AEE/V+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 12/17页 |
| 文件大小： | 0K |
| 描述： | IC REG BUCK 5V/ADJ 0.6A 16QSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,500 |
| 类型： | 降压（降压） |
| 输出类型： | 两者兼有 |
| 输出数： | 1 |
| 输出电压： | 5V，1 V ~ 10 V |
| 输入电压： | 3.5 V ~ 28 V |
| PWM 型： | 电流模式 |
| 频率 - 开关： | 220kHz ~ 1MHz |
| 电流 - 输出： | 600mA |
| 同步整流器： | 无 |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.154"，3.90mm 宽） |
| 包装： | 带卷 (TR) |
| 供应商设备封装： | 16-QSOP |
MAX16976
28V, 600mA Automotive Step-Down Converter
with Low Operating Current
RESET_TIMEOUT =
1.13V × C
26.4 × 10 ( ? x Hz)
f OSC (Hz) ≈
L = OUT SUPSW OUT
3.65 clock cycles. The device waits for the next 3.65
clock cycles to finish. As a result, the soonest the LX
node can go below ground is 4 + 3.65 = 7.65 clock
cycles. This time does not factor in the size of the induc-
tor and the time it takes for the inductor current to build
up to 100mA (internal load).
No load minimum time before refresh is:
?T (no load) = 7.65 clock cycles = 7.65 x 4.54μs (at
220kHz) = 34.73μs
Assuming a full 100mA is needed to refresh the BST capac-
itor and depending on the size of the inductor, the time it
takes to build up full 100mA in the inductor is given by:
?T (inductor) = L x ?I/?V (current build-up starts from the
sixth clock cycle)
L = inductor value chosen in the design guide.
?I is the required current = 100mA.
?V = voltage across the inductor (assume this to be
0.5V), which means V IN is greater than V OUT by 0.5V.
If ?T (inductor) < 7.65 – 6 (clock cycles) then the BST
capacitor is sized as follows:
BST_CAP ≥ I_BST(dropout) x ?T (no load)/?V (BST
capacitor)
?T (no load) = 7.65 clock cycles = 34.73μs.
?V (BST capacitor), for (3.3V to 5V) output = V OUT – 2.7V
(2.7V is the minimum voltage allowed on the BST capaci-
tor).
If ?T (inductor) > 7.65 - 6 clock cycles then we need to
wait for the next count of 3.65 clock cycles making ?T (no
load) = 11.65 clock cycles.
Assume ?T (no load) to be 16 clock cycles when design-
ing the BST capacitor with a typical inductor value for
220kHz operation.
The final BST_CAP equation is:
BST_CAP = I_BST (dropout) x ?T (no load)/?V (BST
capacitor)
where:
I_BST (dropout) = 2.5mA (worst case)
?T (no load) = 16 clock cycles
(s)
10 μ A
where C is the capacitor from CRES to GND in Farads.
Internal Oscillator
The device’s internal oscillator is programmable from
220kHz to 1.0MHz using a single resistor at FOSC. Use
the following formula to calculate the switching frequency:
9
R
where R is the resistor from FOSC to GND in ohms.
For example, a 220kHz switching frequency is set with
R FOSC = 120k I . Higher frequencies allow designs with
lower inductor values and less output capacitance.
Consequently, peak currents and I 2 R losses are lower
at higher switching frequencies, but core losses, gate-
charge currents, and switching losses increase.
Inductor Selection
Three key inductor parameters must be specified for
operation with the device: inductance value (L), inductor
saturation current (I SAT ), and DC resistance (R DCR ). To
select inductance value, the ratio of inductor peak-to-
peak AC current to DC average current (LIR) must be
selected first. A good compromise between size and loss
is a 30% peak-to-peak ripple current to average-current
ratio (LIR = 0.3). The switching frequency, input voltage,
output voltage, and selected LIR then determine the
inductor value as follows:
V (V - V )
V SUPSW f SW I OUT LIR
where V SUPSW , V OUT , and I OUT are typical values (so
that efficiency is optimum for typical conditions). The
switching frequency is set by R FOSC . The exact inductor
value is not critical and can be adjusted to make trade-
offs among size, cost, efficiency, and transient response
requirements. Table 1 shows a comparison between
small and large inductor sizes.
Table 1. Inductor Siz e Comparison
INDUCTOR SIZE
?V (BST capacitor) = V OUT - 2.7V
Reset Timeout Period
The device offers a capacitor-adjustable reset timeout
period. CRES can source 10 F A of current. Use the fol-
lowing formula to set the timeout period.
SMALLER
Lower price
Smaller form-factor
Faster load response
LARGER
Smaller ripple
Higher efficiency
Larger fixed-frequency
range in skip mode
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